see first attach
geog x
one page12 hours
1. During this semester we analyzed different types of lava/magma. Please name and describe the characteristics of the major lava/magma types that exist on Earth. Please be very specific
2. Please explain which chapter you enjoyed/learned the most from this class (state your opinion). Please be specific if you want to get full credit.
Chapter 5
Introduction to Natural Hazards
Dr. Joao Santos
Chapter 5
Introduction to Natural Hazards
Dr. Joao Santos
© 2012 Pearson Education, Inc.
Case History: Hurricane Katrina (1)
• Made Landfall in August 29, 2005 to the east of
New Orleans
• Storm Surge: 3 to 6 m (9 to 20 ft)
• Diameter of serious damage path: About 160
km (100 mi)
• 80 percent of New Orleans under water
• Official number of deaths: 1,836
• Property damages: Tens of billions
• Estimated costs for recovering and rebuilding:
hundreds of billions
© 2012 Pearson Education, Inc.
Case History: Hurricane Katrina (2)
• Regional subsidence: 1 to 4 m (3 to 12 ft) per 100 yrs
• Sea level rise: 20 cm (8 in.) last 100 yrs due to global
warming and extraction of GW, oil and gas
• Geographic location: Vulnerable to hurricanes, storms,
and inland floods
• Aware of risks and warnings in place
• Insufficient funds for monitoring and maintaining the
levee and floodwalls
• Poor coordination in initial emergency response efforts
• Rebuild: Better design and planning, better technology
and knowledge, broader awareness
© 2012 Pearson Education, Inc.
Hurricane Katrina
Figure 5.1
© 2012 Pearson Education, Inc.
Natural Disaster, Hazards (1)
• Criteria: A particular event in which 10 or more
people are killed; one hundred or more people
are affected; a declaration of emergency is
issued, or there is a request for international
assistance
• Dangerous natural processes, including
earthquakes, floods, volcanic activities,
landslides, and storms
© 2012 Pearson Education, Inc.
Natural Disaster, Hazards (2)
• The occurrences of natural disasters on a world
scale are increasing
• Natural disaster causing great loss of life and/or
property damage
• Earthquakes, floods, cyclones (hurricanes) killed
several million people, with an average worldwide
annual loss of life of about 150,000 people
• Annual average property damage exceeds $50
billion
• Impact risks, depending on the nature of hazards,
spatial and temporal relations to human
environment
© 2012 Pearson Education, Inc.
From NOAA 99044-CD
Types of Natural Hazards
© 2012 Pearson Education, Inc.
Why Natural Processes Become Hazards
• Natural processes become hazardous: When
people live or work in areas where they occur
• Land-use changes, such as urbanization or
deforestation
• Better environmental planning:Simply not to
build on floodplains, earthquake prone areas
• Consumption of energy resources and climate
changes
© 2012 Pearson Education, Inc.
Hazard Magnitude and Frequency
• Magnitude: Intensity of a natural hazard in terms
of the amount of energy released
• Frequency: Recurrence interval of a disastrous
event
• Magnitude and Frequency: Generally an inverse
relation between them
• More damages associated with hazards of
moderate frequency and magnitudes
© 2012 Pearson Education, Inc.
Magnitude, Frequency, and Impact Risk
• Magnitude and Frequency: Largely controlled by
natural factors
• Impact risk: Controlled by both natural and human
factors
• Low-magnitude and high-frequency hazards not
always destructive, a high magnitude one almost
certainly catastrophic
• Commonly, most impact risks from natural
processes of moderate magnitude and moderate
frequency
© 2012 Pearson Education, Inc.
Mixed Blessings of Natural Hazards
• Not all hazardous processes exert harmful or
deadly consequences
• Benefits: Creating new land, supplying nutrients
to soil, flushing away pollutants, changing local
landscape
• Fault gouge has formed groundwater barriers,
producing natural subsurface dams and water
resources
© 2012 Pearson Education, Inc.
Damages of Natural Hazards (1)
• Death and damages: Great loss of human life,
grave damages to property, changes in
properties of Earth materials
• More life loss from a major natural disaster in a
developing country; more property damage in a
more developed country
• Catastrophe: Disastrous situations requiring a
long process to recovery from grave damages
© 2012 Pearson Education, Inc. Table 5.1
Catastrophic Potential of Hazards
© 2012 Pearson Education, Inc.
Hazard Evaluation (1)
Fundamental Principles
• Most natural hazards: Identified and studied using the
scientific method and predictable from scientific
evaluation
• Risk analysis: A critical component in understanding
impacts
• Different hazards are linked
• Hazardous events repetitive
• Importance of hazard planning and hazard mitigation
© 2012 Pearson Education, Inc.
Hazard Evaluation (2)
• Study historic data: Hazards are repetitive
events
– Occurrence and recurrence intervals
– Location and effects of past hazards
– Observations of present conditions
– Measuring the changes or rates of change
– Historic trends of hazards
© 2012 Pearson Education, Inc.
Hazard Evaluation (3)
• Studying linkages: Spatial and temporal links
– Linkages between adjacent locations
– Linkages between past, present, and future
conditions
– Linkages between hazards (e.g., volcano and
mudflow)
– Geologic setting and hazards (e.g., rock fractures
and landslides)
© 2012 Pearson Education, Inc.
Disaster Forecast, Prediction, and
Warning (1)
• Forecast: The certainty of the event is given as
the percent chance of happening
• Prediction: Sometimes possible to accurately
predict when, where, type and size of the
certain natural hazardous events
• Warning: A hazardous event has been
predicted or a forecast has been made, the
public must be warned
© 2012 Pearson Education, Inc.
Disaster Forecast, Prediction, and
Warning (2)
• Locations, precursors, probability of occurring
• Determining the probabilities of a hazardous
event at a given magnitude
• Observing precursor events or signs
• Forecasting the hazard
• Warning the public
© 2012 Pearson Education, Inc.
Disaster Prediction and Warning (2)
Figure 5.14
© 2012 Pearson Education, Inc.
Scientists, Hazards, and the Media
• The media are generally more interested in the impact of
a particular event on people than in its scientific aspects
• Good relations between scientists and the news media is
a goal that may be difficult to always achieve
• Scientists have an obligation to provide the public with
information about natural hazards
• Reports concerning people’s lives and property should be
conservative evaluations based on the evidence at hand
• Provide their readers, viewers, or listeners with accurate
information that have been verified
© 2012 Pearson Education, Inc.
Risk Assessment
• Risk determination
– Type, location, probability, consequences
– Risk estimate: Product of probability and
consequences
• Risk Threshold: Acceptable risks
– Put probability and consequences into perspective
– Society’s perception and willingness
• Limitations and opportunities of risk assessment
© 2012 Pearson Education, Inc.
Risk Impact (1)
Hazardous Earth processes and risk impact
statistics for the past two decades
• Annual loss of life: About 150,000
• Financial loss: > $50 billions
• More life loss from a major natural disaster in a
developing country (2003 Iran quake, ~30,000
people)
• More property damage occurs in a more
developed country
© 2012 Pearson Education, Inc.
Risk Impact (2)
Risk impact estimation:
• To human life: Potential loss and injury of life
• To property: Damage and destruction
• To society: Services and functions of society
• To economy: Manufacture, mining, commercial,
real estate, etc.
• To natural environment: Direct or indirect
adverse impact
© 2012 Pearson Education, Inc.
Human Response to Hazards (1)
Reactive response
• Primarily after the hazardous event
• Recovery phases: Search response, rescue,
restoration, and reconstruction
• Recovery period: Recovery length depending on
the magnitude of hazard and impact intensity
© 2012 Pearson Education, Inc.
Human Response to Hazards (2)
Reactive response and recovery priority
• Critical needs: Emergency operations, critical
infrastructure, hospitals, shelter, food, and water
supply
• Essential function: Transportation, communication,
education, and other services
• Improvement and development: Rebuild damaged
structures and develop better structures
© 2012 Pearson Education, Inc.
Human Response to Hazards (3)
Anticipatory Response: Perceiving, Avoiding, and
Adjusting to Hazards for avoiding or minimizing
the impacts of disasters
• Land-use planning
• Insurance and other regulations for safety
measures
• Evacuation
• Disaster awareness and preparedness:
Individuals, families, cities, states, or even
entire nations can practice
© 2012 Pearson Education, Inc.
Human Response to Hazards (4)
General response in a given location
• Combination of reactive and anticipatory
response
• Artificial control of natural processes
• Taking no or little action, being optimistic about
chances of making it through disasters
© 2012 Pearson Education, Inc.
Figure 5.19
Global Climate and Hazards
© 2012 Pearson Education, Inc.
Population Growth and Natural Hazards
• Increase in population puts a greater number of people
at risk
• Asia suffered the greatest losses from 1985 to 1997,
with 77 percent of the total deaths and 45 percent of
the economic losses
• Deadly catastrophes resulting from natural hazards
linked to changes in land use, Hurricane Mitch in 1998,
flooding of the Yangtze River in 1998, and Hurricane
Katrina in 2005
• In quest: Artificially controlling some natural hazards
© 2012 Pearson Education, Inc.
Land-Use Change and Natural Hazards (1)
• Land-use change amplifying the impact risks of
natural hazards
• Deforestation and fire in Honduras before
Hurricane Mitch, 11,000+ deaths
– Massive deforestation in major river basin (e.g.,
85 percent forest loss in Yangtze River, 4000+
deaths)
– Inappropriate construction code in tectonic
earthquake zone, 2003 Iran earthquake, ~300,000
deaths
– Poor construction in Haiti, 2010 earthquake, above
300,000 death
© 2012 Pearson Education, Inc. Figure 5.20
Land-Use Change and Increase in
Natural Hazards (2)
© 2012 Pearson Education, Inc.
Applied and Critical-Thinking Topics
• List all the natural hazardous processes in the are
where you live. What is done? What is more to be
done?
• Construct a U.S. vulnerability map of natural
hazards by state, or construct a state map by
county.
• What is the difference between forecasting and
warning
• Can humans eventually control the impact risks of
natural hazards? Explain your rationale.
© 2012 Pearson Education, Inc.
End of Chapter 5
Chapter 18
Global Climate Change
Dr. Joao Santos
Chapter 18
Global Climate Change
Dr. Joao Santos
© 2012 Pearson Education, Inc.
Case History: Potential Consequences
of
Global Warming
• Approximate 300 year period (1000 to 1300), Earth
was considerably warmer than normal, known as
the Medieval Warming Period (MWP)
• Followed by the Little Ice Age (LIA): Mid
1400
to
1700, difficult for people in Southeast Asia and
Western Europe
• The collapse of the Ankorian civilization part due to
the onset of the LIA
• Crop failures in Western Europe during the LIA, the
population devastated by the Black Plague about
1400
© 2012 Pearson Education, Inc.
Case History: Potential Consequences
of Global Warming
• Famous Viking explorer Eric the Red’s voyage near the
end of tenth century, a period of warm climate
(Medieval Warming period)
• The Vikings colonized Iceland, Greenland, and
northern North America
• Sea temperature probably 4°C (7°F) warmer than
now
• Little Ice Age started early fourteenth century, creating
treacherous sea conditions, famine, spread of the
Black Plague
• Climate changes believed to cause the abandonment
of Viking settlements in North America and Greenland
© 2012 Pearson Education, Inc.
Global Change: An Overview
• Climate changes: Contributing to the complex
evolutionary history of the Earth system
• Earth system: Interactions between the
atmosphere, the oceans, solid Earth, and the
biosphere
• The effects of human activities: Extensive on a
global scale
• Apply the better understanding to better
manage the environment
© 2012 Pearson Education, Inc.
Tools for Studying Global Change
• Geologic Records:
• Sediments deposited on floodplains or in lakes,
bogs, glaciers, or the ocean
• Carbon dioxide concentration in glacial ice, as
old as 800,000
years
• Real-time monitoring: Good for testing models
and predictions from prehistoric record
• Mathematical models: Global circulation models
(GCMs)
© 2012 Pearson Education, Inc.
Geologic Record (Marine/Ocean Cores)
© 2012 Pearson Education, Inc.
Geologic Record (Ice Cores)
© 2012 Pearson Education, Inc.
Atmosphere and Climate Change
• Atmosphere as a complex chemical factory: with
many little-understood chemical reactions
• Many of the reactions strongly influenced by
both sunlight and the compounds produced
by life
• Climate change: Change of atmosphere
conditions and its relationships with lithosphere,
hydrosphere, and biosphere
• Changes in greenhouse gases, variable
temperature, and water vapor
© 2012 Pearson Education, Inc.
The Greenhouse Effect (1)
• Temperature of Earth: Determined by three
factors
– The amount of sunlight received
– The amount of solar energy reflected and absorbed
– The amount of heat retention by atmosphere
• Earth: Absorbing the short wavelength solar
energy, then radiating longer wavelength IR
radiation
© 2012 Pearson Education, Inc.
The Greenhouse Effect (2)
• Several atmospheric gases: Water vapor and
several other atmospheric gases, including CO2,
CH4, NOx, CFCs, trapping more heat and
warming up the lower atmosphere, similar to the
effect of a greenhouse
• The concentration of greenhouse gases
increased recently due to human activities,
anthropogenic gases
© 2012 Pearson Education, Inc.
Study Past Climate Change
• The Instrumental Record: Started in 1860s, today
temperature measured at about 7,000 stations
around the world
• The Historical Record: Books, newspapers,
journal articles, personal journals
• The Paleo-Proxy Record: Proxy data refers to
data that is not strictly climatic but that can be
correlated with climate, such as temperature of
the land or sea: ice core, tree rings, pollen,
corals, carbon-14, carbon dioxide, and methane
data
© 2012 Pearson Education, Inc.
Dendrochronology (Tree Rings)
© 2012 Pearson Education, Inc.
Carbon Dioxide in the Atmosphere
© 2012 Pearson Education, Inc.
Global Warming
• Global warming: The observed increase in the average
temperature of the near-surface land and ocean
environments of Earth
• Human processes (in the past 100 years), as well as
natural ones (over geologic time) contributed
significantly to global warming
• Recent global warming is believed to be due in a large
part to human emissions of greenhouse gases
• Based on equivalent amount of the global warming
potential (GWP), carbon dioxide accounted for
85.1 percent, methane 8.2 percent, nitrous oxide
4.6 percent, and chlorofluorocarbons 2.2 percent
© 2012 Pearson Education, Inc.
Increase in Greenhouse Gasses
© 2012 Pearson Education, Inc.
Global Temperature Change
• The Pleistocene Ice Age: ~ 2 mya, peaked at
18,000 years ago
• Numerous changes in Earth’s mean annual
temperature since then
• Warming trend over the last 140 years, first 8
years of the twenty-first century had the
warmest temperatures
• Mean temp increased about 0.8°C (1.36°F) in
the past 100 years
© 2012 Pearson Education, Inc.
Global Temperature Data from the U.S.
(NOAA) and Europe (WMO)
© 2012 Pearson Education, Inc.
Why Climate Change?
• Changes in long cycles (100,000 years)
separated by short cycles (23,000 to 41,000
years)
• First identified in 1920s, Milankovitch hypothesis
• Long cycle: The variability in Earth’s orbit
around the Sun
• Short cycle: The tilt of Earth’s axis
© 2012 Pearson Education, Inc.
Milankovitch Cycles and Climate Change
Milankovitch hypothesis – Climate variation over 100-
300 Ka predicted by cyclic changes in orbital
geometry.
• The shape of Earth’s orbit varies (~ 100,000 year cyclicity)
• Tilt of Earth’s axis varies from 22.5o to 24.5o (~41,000 years)
• Precession – Earth’s axis wobbles like a top (23,000 years)
© 2012 Pearson Education, Inc.
Why Climate Change?
• Climate system even unstable in shorter cycles,
in a few decades
• The ocean conveyor belt, global circulation of
ocean water, contribute to the change
• Discernable human influence, mean
temperature likely 1.5° to 4.5°C (2.6° to
7.8°F) warmer in twenty-first century
• Global warming: Need to consider major forcing
variables—solar, volcanic, and anthropogenic
gases
© 2012 Pearson Education, Inc.
Solar Forcing
• Historic record of the past 1000 years showing
the variability of solar energy
• Medieval Warm Period (A.D. 1000 to 1300)
corresponding to a time increased solar
radiation
• The Little Ice Age (fourteenth century)
corresponding to the minimum solar activity
• The effect relatively small, 0.25 percent
© 2012 Pearson Education, Inc.
Volcanic Forcing
• Volcanic eruption: Vast amount of aerosol
particles into the air
• Aerosols: Reducing solar radiation to Earth
surface
• Episodes of volcanic eruptions having a
significant contribution to the cooling of the
Little Ice Age
© 2012 Pearson Education, Inc.
Anthropogenic Forcing
• Natural variability failing to explain the warming
at end of the twentieth century
• Mathematical modeling on the anthropogenic
forcing: increase of temperature 2°C due to the
doubling of CO2
• Significant global warming as a result of human
activities, air pollution reduced incoming solar
energy by 10 percent which offsetting up to 50
percent of the expected warming
© 2012 Pearson Education, Inc.
Potential Effects of Global Climate
• Doubling the greenhouse gases, then 1.5° to
4.5°C (2.6° to 7.8°F) increase in average
global temperature
• Significant rise of sea level and melting of
glacier ice due to the increase in temp
• The number of retreating glaciers accelerating
in many areas of the world (ex. Alaska)
• Significant effects on global climate patterns
© 2012 Pearson Education, Inc.
Glaciers and Global Warming
• Loose snow has about 90 percent air compared to firm,
with about 25 percent air to glacial ice with less than
20 percent air as bubbles
• Transformation from snow to glacial ice: 10s to 1000s of
years
• Global warming: Accelerated melting of glacial ice
• Exposed bare ground after glacial ice melts produces a
positive feedback cycle: The more ice that melts, the
faster the warming and increased melting
• The lowest extent of sea ice in the Atlantic Ocean in 2007
• The Antarctic Peninsula: One of the most rapidly warming
regions on Earth
© 2012 Pearson Education, Inc.
Extent of Sea Ice
© 2012 Pearson Education, Inc.
Change in Climate Patterns
• Global warming leads to significant changes of
rainfall and soil moisture (draught and flood)
• Agricultural activities (crop growth cycle) and
world food supplies affected greatly by climatic
factors (desertification)
• Global warming affects the frequency, intensity,
and distribution of natural hazards, such as
hurricane and other storms
© 2012 Pearson Education, Inc.
Sea Level Rise and Global Warming
• An estimated 40 to 200 cm (16 to 80 in.), wide
range of rise in sea level for the next century
• Increases in coastal erosion: Up to 260 ft on
open beaches by stronger wave actions
• Landward shift of existing estuaries
• Disastrous impact on the existing developments
along coastal zones
© 2012 Pearson Education, Inc.
Biosphere and Global Warming
• Causing a number of changes in biosphere,
both people and overall ecosystem
• Risk of extinction due to land-use change and
habitat shift
• Spread of infectious and other diseases due to
migration of organisms
• Both land and oceanic components affected:
from plants, to polar bears, to the bleaching of
coral reef
© 2012 Pearson Education, Inc.
Adaptation of Species to Global Warming
• During the past 25 years or so, plants and
animals shifted their ranges by about 6
kilometers per decade toward the polar areas
• Spring arriving earlier, migrating birds arriving
earlier, about 2.3 days per decade
• In Costa Rica, over 60 species of frogs may
have gone extinct
• Assist migration of some species, unable to
migrate with climate change, creating an
invasive species, problematic
© 2012 Pearson Education, Inc.
Strategies for Reducing the Impact of
Global Warming (1)
• Identify the historic changes that have occurred
• Predict the potential changes in the future:
through modeling and simulation
• Reduce greenhouse gases
• Political commitment: Reconciling the conflicts
between the environmental need for reduction
of greenhouse gases and the economic
demands for more fossil fuel
© 2012 Pearson Education, Inc.
Strategies for Reducing the Impact of
Global Warming (2)
• The Kyoto Protocol, international agreement to
reduce emissions of greenhouse gases, signed
by 166 nations and became a formal
international treaty in February 2005
• Scientific evidence suggests that burning fossil
fuels is contributing significantly to global
warming
• Even if carbon emissions were reduced to zero,
warming will continue this century. There is
0.5° to 1.0°C warming in the system
© 2012 Pearson Education, Inc.
Strategies for Reducing Global Warming
(3)
© 2012 Pearson Education, Inc.
Reducing the Impact of
Global Warming (4)
Reduce the emission of CO2
• Improved engineering technologies of the fuel-
burning power plants
• Use fossil fuels releasing less CO2
• Conservation of energy
• Store CO2 in forests, soils and rocks, depleted
oil and gas fields, saltwater aquifers
(sequestration of CO2)
• Use alternative energy
© 2012 Pearson Education, Inc.
End of Chapter 18
Chapter 15
Mineral Resources and Environment
Dr. Joao Santos
Chapter 15
Mineral Resources and Environment
Dr. Joao Santos
© 2012 Pearson Education, Inc.
Minerals and Human Use
• Backbone of modern societies
• Availability of mineral resources as a measure
of the wealth of a society
• Important in people’s daily life as well as in
overall economy
• Processed materials from minerals accounting
for 5 percent of the U.S. GDP
• Mineral resources are nonrenewable
© 2012 Pearson Education, Inc.
Common Use of Mineral Products
© 2012 Pearson Education, Inc.
Mineral Resources and Reserves
• Mineral resources: Usable economic commodity
(profitable) extracted from naturally formed
material (elements, compounds, minerals, or
rocks)
• Reserve: Portion of a resource that is identified
and currently available to be extracted legally
• Defining factors: Geologic, technological,
economic, and legal factors
© 2012 Pearson Education, Inc.
Mineral Resources and Reserves
© 2012 Pearson Education, Inc.
Types of Mineral Resources
Based on how we use them
• Materials for metal production and technology
• Construction materials
• Agricultural industry (fertilizers)
• Mineral resources for chemical industry
• Others (precious gem stones, cosmetics, food,
etc.)
• Energy mineral resources
© 2012 Pearson Education, Inc.
Mineral Resources Problems
• Nonrenewable resources
• Finite amount of mineral resources and growing
demands of the resources
• Supply shortage due to the growing global
industrialization, with more developed countries
consuming disproportionate share of mineral
resources
• The erratic distribution of the resources and uneven
consumption of the resources. Highly developed
countries use the most of the resources
© 2012 Pearson Education, Inc.
Responses to Limited Availability
• Find more sources
• Find a substitute
• Recycle
• Use less and make more efficient use of what
is available
• Do without
© 2012 Pearson Education, Inc.
Responses to Limited Availability
© 2012 Pearson Education, Inc.
Geology of Mineral Resources
Metallic ore: Useful metallic minerals that can
be mined for a profit
• Mining potential depending upon technology,
economics, and politics with an emphasis on
profitability, technological feasibility, and demands
• Concentration factor: Concentration necessary
for profitable mining (e.g., for gold is about 5,000)
– Variable with types of metals
– Variable over time
© 2012 Pearson Education, Inc.
Genesis of Mineral Resources
© 2012 Pearson Education, Inc.
Plate Tectonics and Minerals
• Plate tectonic boundaries related to the origins of
many ore deposits, Fe, Au, Cu, and Hg, etc.
• Plate tectonic processes (high temp, high pressure,
and partial melting) promoting release and
enrichment of metals along plate boundaries
• Ore deposits at divergent boundaries is related to the
migration (movement) of ocean water
• Ore deposits at convergent boundaries: Related to
partial melting of seawater-saturated rocks of the
oceanic lithosphere in a subduction zone
• Danger in oversimplification, not all directly related to
plate boundaries
© 2012 Pearson Education, Inc.
Other Minerals from the Sea
Mineral resources on the bottom of the ocean are vast
• Sulfide deposits: Massive sulfide deposits containing zinc,
copper, iron, and trace amounts of silver are produced at the
black smokers along the oceanic ridges, from which the hot,
dark-colored, mineral-rich water emerges as hot springs
• Manganese oxide nodules: cover vast areas of the deep-
ocean floor (up to 50 percent in certain area), containing
manganese (24 percent) and iron (14 percent), with
secondary copper (1 percent), nickel (1 percent), and cobalt
(0.25 percent). Most abundant in where sediment is at a
minimum, generally at depths of 5 to 7 km
• Cobalt-enriched manganese crusts: Present in the mid- and
southwest Pacific, on flanks of seamounts, volcanic ridges,
and islands
© 2012 Pearson Education, Inc.
Mineral Resources and
Environmental Impact
Environmental impact
• From mineral exploration and testing
• From mineral mining
• From mineral resources refining
• From mining waste disposal
© 2012 Pearson Education, Inc.
Environment Impact
The impact depends upon many factors
• Mining procedures
• Hydrologic conditions
• Climate factors
• Types of rocks and soils
• Topography
© 2012 Pearson Education, Inc.
Impact from Exploration and Testing
• Mineral exploration and testing
– Surface mapping, geochemical, geophysical, and
remote-sensing data collection
– Test drilling
• Impact
– Generally minimal impact
– More planning and care needed for sensitive areas
(arid, wetlands, and permafrost areas)
© 2012 Pearson Education, Inc.
Impact of Mineral Extraction
and Processing (1)
General impact
• Direct impact on land, water, air, and biological
environment
• Indirect impact on the environment: Topographic
effect, transportation of materials, etc.
• Impact on social environment: Increased
demands for housing and services
© 2012 Pearson Education, Inc.
Impact of Mineral Extraction
and Processing (2)
Impact from mining operations
• Land disturbances from access, surface mining (more
economical but more direct environmental effects)
• Waste from mines: 40 percent of the mining area for
waste disposal, mining waste 40 percent of all solid
wastes
• Special mining (e.g., chemical leaching from gold
mining)
• Mining acid drainage, during mining and post mining
• Water pollution, such as smelting emissions of SO2
• Biological environment
© 2012 Pearson Education, Inc.
Impact of Mineral Extraction
and Processing (3)
© 2012 Pearson Education, Inc.
Impact of Mineral Extraction
and Processing (4)
Water pollution
• Trace elements leaching out into water, such as
Cd, Co, Cu, Pb, Mo, Zn
• Flooding of abandoned mine
• Acid mine drainage from tailings
• Acidic and toxic mining wastewater
© 2012 Pearson Education, Inc.
Impact of Mineral Extraction
and Processing (5)
Other pollution
• Air pollution: Both extraction and processing
operations have adverse effects on air quality;
smelting has released enormous quantities of
pollutants; toxic gases from abandoned mines
• Pollution to overall biological environment:
Physical and chemical changes in the land, soil,
water, and air associated with mining directly
and indirectly affect the biological environment
© 2012 Pearson Education, Inc.
Mining and Toxicity
• Itai-Itai Disease: Chronical and painful (itai-itai
means “ouch, ouch”), attacks bones.
• The bones and tissues of victims were
examined and found to contain large
concentrations of zinc, lead, and cadmium
• Mercury and gold mining: Gold particles cling to
the liquid metal, mercury making recovery of the
gold easier.
• Estimated 4,500 metric tons of mercury was lost
into the environment, from 1850s–1880s in CA
© 2012 Pearson Education, Inc.
Minimizing the Impact
of Mining
• Knowledge and technology transfer: Developed
countries to developing countries
• Environmental regulations: forbid bad mining
practices, Clean Air Act, and on- and offsite
treatment of wastes
• Land reclamation: About 50 percent of land used
in mining industry reclaimed
• Use of new biotechnology in mining: Bio-
oxidation, bioleaching, biosorption, genetic
engineering
• Practicing the three Rs of waste management
© 2012 Pearson Education, Inc.
Minimizing the Impact
© 2012 Pearson Education, Inc.
Recycling Mineral Resources
(1)
Why recycle? Consider the impact of the wastes
• Toxic to humans
• Dangerous to natural ecosystem
• Degradation of air, water, and soil
• Use of land for disposal
• Aesthetically undesirable
© 2012 Pearson Education, Inc.
Recycling Mineral Resources
© 2012 Pearson Education, Inc.
Recycling Mineral Resources (2)
• Waste contains recyclable materials
• Saves energy, money, land, raw mineral
resources from more mining
• Saves energy and money when recycling
instead of refining raw ore materials
• Recycling has been proven to be profitable and
workable
© 2012 Pearson Education, Inc.
Recycling Mineral Resources (3)
• Most-recycled metals: iron and steel, 90 percent by
weight
• One third as much energy needed to produce steel
from recycled scrap as from original ore
• In 2006, the total value of recycled steel in the United
States was about $18.5 billion, recycling of iron and
steel amounted to approximately 50 percent
• Lead (73 percent, $1.96 billion), aluminum (43 percent,
$9.38 billion), copper (32 percent, $6.72 billion), nickel
(43 percent, $2.62 billion), and titanium (47 percent,
$0.25 billion)
© 2012 Pearson Education, Inc.
Minerals and Sustainability
• Sustainability: Long term strategy for consuming the
resources
• Find an alternative materials for the metal (e.g., glass
fiber cable for copper wires)
• Use raw materials more efficiently. The time available
for finding a solution to the depletion of a nonrenewable
mineral is the R/C ratio, where R is the known reserve
and C is the rate of consumption
• More R&D on innovative substitutes or ways to keep
the R/C ratio, a solution to the depletion of
nonrenewable resources
© 2012 Pearson Education, Inc.
End of Chapter 15
Chapter 16
Energy Resources
Dr. Joao Santos
Chapter 16
Energy Resources
Dr. Joao Santos
© 2012 Pearson Education, Inc.
Introduction
• Fundamental lifeblood for industrialization
• Disproportionate amount of energy resources
demanded and consumed in developed
countries
• Growing challenges: How to break energy
dependency, yet sustain development and high
standard of living
• Energy shocks: Constant worries from past to
present and to the future over the price,
dependency, power failure
© 2012 Pearson Education, Inc.
Case History: Energy Transition 1800–
• The amount of fossil fuels in the Earth is finite
• Energy transformation in the United States from wood in
the mid-1800s to fossil fuels in the mid-1900s, the peak in
use of wood was approximately 1870
• It took something like 100 years for the full transition
• Shortages of wood in 1812 in Philadelphia led to
experiments of burning coal, and the first oil well was
completed in 1858
• Peak oil production (when about one-half of Earth’s
recoverable oil will have been produced and used) is
likely to occur sometime between 2020 and 2050
• Another transition is in the making, from oil to alternative
energy sources
© 2012 Pearson Education, Inc.
Case History: Energy Transition 1800–
© 2012 Pearson Education, Inc.
Energy Shocks Past and Present
• 2000 years ago, affluent Roman citizens had central
heating that consumed vast amounts of wood—
perhaps as much as 125 kg (275 lb) every hour
• To combat the shortages, the Romans had to import
wood from distances as far away as 1600 km (995 mi)
• They turned to solar energy as an alternative
• During the summer of 2008, U.S. citizens were
shocked by the rapid price increase of gasoline
• “California energy crisis” with its rolling blackouts, in
2001 occurred ahead of the gasoline price increase
• Energy crisis: Not new, occurred in historic times
© 2012 Pearson Education, Inc.
Peak Oil
• Benefits of oil: Undeniable
• Problems associated with oil: Unquestionable
• Peak oil: The time when half of Earth’s oil
extracted and used
• Oil: Nonrenewable and being consumed too fast
• Consequences: Growing demands, water
pollution, air pollution, global warming; global,
economic, and political instability
© 2012 Pearson Education, Inc.
Peak Oil
© 2012 Pearson Education, Inc.
Energy Supply and Demand
• Fossil fuels: 90 percent of U.S. energy
consumption (10 percent from hydropower and
nuclear power)
• Fossil fuels nonrenewable resources
• Fossil fuel peak discoveries in 1960s
• U.S. energy consumption increasing over time.
The rate of increase variable: Peak increase
during 1950–1974, since then it has slowed
down
© 2012 Pearson Education, Inc.
Energy Supply and Demand
© 2012 Pearson Education, Inc.
Energy and Energy Units
• Types of energy: Light, electrical, chemical,
thermal, mechanical, and nuclear
• Energy unit: Energy capacity to do work
– Joules (J): 1 Newton force applied over 1 m
– 1 gigajoule (GJ) = 109 J,
– 1 exajoule (EJ) = 1018 J ,
– 1 quad (1015 BTU) = 1.055 EJ
• Power: Rate of energy transferred or used
– Watt (W): 1 joule per second (1 J/sec)
– MW (megawatts): 1000 W
© 2012 Pearson Education, Inc.
Fossil Fuels
• Transformed from the solar energy originally stored
in organic matter
• Organic matter buried and preserved as fossil fuels
• Geologically: Stored in subsurface rock materials
• Types: Coal, petroleum, natural gas
• Environmental
impact
: Significant impact from
exploration, production, processing, and distribution
© 2012 Pearson Education, Inc.
Coal Resources
• America has more coal than any other fossil-fuel
resource.
• 20 percent of the total U.S. energy consumption
• The United States has more coal reserves than
any other single country in the world
• One-quarter of all the known coal in the world is
in the United States
• Large coal deposits can be found in 38 of the 50
states
© 2012 Pearson Education, Inc.
Geology of Coal
• Coal: Transformed plant matter in ancient
swamps
– Estuaries, lagoons, low-lying coastal plains or delta
environment
• Coal forming process
– Massive dead plants� buried in an anaerobic
(O-deficient) environment� peat� prolonged bury
and transformation to increase carbon content�
coal
© 2012 Pearson Education, Inc.
Geology of Coal
© 2012 Pearson Education, Inc.
Classification of Coal
• Based on carbon content and calorific value on
combustion
– Lignite, subbituminous, bituminous, anthracite
• With the increase in rank, generally higher
carbon content, higher calorific values, less
volatile gas, and less moisture content
• Based on sulfur content: low (< 1 percent), medium (1 to 3 percent), and high (> 3 percent)
© 2012 Pearson Education, Inc.
Coal Distribution and Consumption
• World reserves about 1000 BMT (billion metric
tons)
• Relatively evenly distributed throughout the
world
• U.S. reserves: 25 percent of the world reserves
• Annual global consumption 5 BMT
• China, United States, and Russian account for
50 percent of total CO2 released
© 2012 Pearson Education, Inc.
Distribution of Coal (2)
© 2012 Pearson Education, Inc.
Impact of Coal Mining
• Land disturbances from open-pit and strip
mining
• Mining area acid drainage
• Subsidence over subsurface mines
• Surface water and groundwater pollution
• Air pollution from thermoelectric power plant
• Area ecosystem degradation due to mining
practice and afterward inadequate land
reclamation
© 2012 Pearson Education, Inc.
Future Use and Environmental
Impacts of Coal
• More and more land will be strip mined
• Disposal of coal ash (5–20 percent of original coal)
• Mining, processing, disposal of mining waste,
shipping, burning, and disposing of ash: All
potentially adverse to environment
• Fly ash, from burning finely ground coal in a power
plant, hazardous
• The use of coal releasing huge amounts of carbon
dioxide (CO2) into the atmosphere
• China, the United States, and Russia: The major
carbon dioxide contributors
© 2012 Pearson Education, Inc.
Hydrocarbon: Oil and Gas
• Oil and gas (O&G): Hydrocarbons due to
chemical composition of C, H, and O
• Natural gas: Mostly methane (CH4)
• O&G: Formed from transformation of organic
matters
• Heavily mined through production wells
• Other forms: Oil shale and tar sands
© 2012 Pearson Education, Inc.
Geology of Oil and Gas (1)
• Formation of O&G
– Rapid bury�
– Anaerobic environment�
– Biogenic or thermogenic transformation�
– Oil window (approximately 3 to 6 km depth)
– Formation of oil and gas�
– O&G trapped over geologic time in certain structures
© 2012 Pearson Education, Inc.
Geology of Oil and Gas (2)
© 2012 Pearson Education, Inc.
Geology of Oil & Gas (3)
Geologic conditions for O&G fields
• Source rock: Fine-grained organic-rich
sedimentary rocks, then O&G migrating upward
to the reservoir rocks
• Reservoir rock: Porous and permeable rocks
• Cap rock:Impermeable rock as a barrier to trap
O&G in place, forming oil fields
© 2012 Pearson Education, Inc.
Oil & Gas Production
Production: Commonly through wells
• Types of production
– Primary recovery: Pump no more than 25 percent of
the petroleum in the field under natural reservoir
pressure
– Enhanced recovery: Manipulate reservoir pressure
by injecting gases and liquids, 50 to 60 percent of
the petroleum
© 2012 Pearson Education, Inc.
Distribution of Oil and Gas (1)
• Almost exclusively from sedimentary rocks
younger than 500 million years
• ~ 85 percent of the total production in less than
5 percent of production fields
• ~ 65 percent of the total production from about
1 percent of the giant fields
• Most giant O&G fields near recently active plate
boundaries in the last 70 million years
© 2012 Pearson Education, Inc.
Distribution of Oil and Gas (2)
© 2012 Pearson Education, Inc.
Natural Gas
• Larger global reserve, lasting 100 years at
current rate of consumption
• The most reserves in Russia and Middle East
• Cleaner fuel than oil and coal
• Methane hydrate: May be future alternative
energy source
© 2012 Pearson Education, Inc.
Coal-Bed Methane
• Coal containing a large amount of methane
• The methane reserves in WY sufficient for the U.S.
natural gas use for 5 years
• Most coal-bed methane shallow and more
economical to drill
• Concerns over extraction processing and
transportation
• Environmental problems associated with production,
such as disposal of salty water, a flammable
process, erosion
© 2012 Pearson Education, Inc.
Methane Hydrate
• Potential good source of natural gas
• Exist at depths of 1,000 m (3,300 ft) beneath the
sea and under permafrost land areas
• White, ice-like compound of methane gas
capsulated by frozen water
• Complicated processes for exploration and
production due to highly pressurized conditions
• More studies need to be done for exploiting it
© 2012 Pearson Education, Inc.
Impact of Exploration & Production
• Land disturbance: Access, drilling
• Environmental impact: Production,
transportation, and emissions from refinery
• By-products: Salty brine water, evaporation, and
waste disposal problems
• Oil field development in sensitive areas
• Blow-outs or fire at oil and gas wells
• Acid rain
© 2012 Pearson Education, Inc.
Oil Shales and Tar Sands
• Best-known oil shale in the United States found in
Green River Formation
• Approximate 44,000 km2 in CO, UT, and WY
• ~ 2 trillion (MMBOL) in United States, two-thirds of
the world’s oil shale
• Tar sands contain tar oil and asphalt and other
semi-solid or solid petroleum products
• Tar sands not necessarily sandstone, can be shale,
limestone, or unconsolidated sediments
• Largest tar sands: the Athabasca Tar Sands in
Alberta, Canada, ~ 78,000 km2 (2 trillion BOL)
© 2012 Pearson Education, Inc.
Future of Oil
• Approaching the peak oil time
• About 3 trillion barrels of oil be recovered
• World current consumption rate: 30 billion
barrels/yr
• Estimated peak production 2020 to 2050
• Significant oil production in the United States
not extend beyond 2090
• Planning, education, research and development
on alternative energy sources: Gasification and
liquefaction of coal, other renewable sources
© 2012 Pearson Education, Inc.
Fossil Fuel and Acid Rain
• Acid rain: A regional to global environmental
problem
• Both wet and dry acid deposition:
• Sulfur dioxide (SO2) and nitrogen oxides (NOx)
• In the United Sates, about 17 million tons of NOx
and 13 million tons of SO2 into the atmosphere
• Geology, climate patterns, type of vegetation, and
composition of soil affected
© 2012 Pearson Education, Inc.
Fossil Fuel and Acid Rain
© 2012 Pearson Education, Inc.
Nuclear Energy
• 440 nuclear reactors provide 16 percent global
electricity needs
• Mostly from fission of U-235, 0.7 percent
concentration naturally, enriched to 3 percent
before used in a reactor
• Fission of 1 kg of U equivalent to the burning of
16 metric tons of coal
© 2012 Pearson Education, Inc.
Geology and Distribution of U
• Average natural concentration 2 ppm
• Must have a concentration factor of 400 to 2500
times to be mined at a profit
• Three types of common deposits: Sandstone
impregnated with U, veins of U-bearing
materials, and old placer deposits
© 2012 Pearson Education, Inc.
Reactor
• Most of the reactors: Burner reactors
• Four main components of burner reactors: Core,
control rods, coolant, and reactor vessel
• Trend of smaller reactors with less complex in
design and gravity-influenced cooling system
(passively safe)
• Gas-cooled reactor, “pebble-bed reactor,” to be
available in the next few years, preventing the
risk of core meltdown and providing optimal
energy production
© 2012 Pearson Education, Inc.
Risks with Fission Reactors
• Various amounts of radiation to environment,
from mining, processing, transportation, and
before transportation
• Potential nuclear reactor accidents, TMI and
Chernobyl
• Nuclear weapons, terrorist activity, and possibly
war
• Disposal of nuclear wastes
© 2012 Pearson Education, Inc.
Nuclear Energy from Fusion
• Combining lighter elements to produce heavier
ones, releasing energy
• The Sun and other stars: Huge nuclear fusion
reactors
• Nuclear fusion: Research objective, not a
commercial reality yet
• Environment: Little radioactive waste, unlimited
supply
• Technology: Under the development
© 2012 Pearson Education, Inc.
Geothermal Energy
• Extracting energy associated with heat and
pressure from natural hot water and steam
• Generating electricity at many sites of world or
heating energy for buildings, etc.
• Vast amount of geothermal energy resources
(500 times of oil and gas resources), only 1
percent could be captured from upper 10 km
© 2012 Pearson Education, Inc.
Risks with Geothermal Energy
• Overall, environmentally friendly with a great
potential for the future energy
• Expensive production process
• Thermal pollution from hot waste waters
• Land subsidence
• At present, relatively local and regional
operations
© 2012 Pearson Education, Inc.
Renewable Energy Sources
• Solar energy: Rapid growing
• Hydropower: Hydroelectric, tidal power
• Biofuels: Wood, charcoal, burning of municipal
waste, currently only 1 percent U.S. municipal
wastes recovered for energy and 10 percent
can be extracted, 30 to 50 percent of wastes for
energy in western Europe
• Wind power: Less than 1 percent global
electricity demand, but 10 percent potential in a
few decades
© 2012 Pearson Education, Inc.
Conservation, Efficiency, and
Cogeneration
• Highly variable future supply of and demand for
energy
• Need to minimize energy demand and adjust
energy uses
• Increase energy efficiency through improved or
new technologies
• Cogeneration: Capture and use some of the
waste heat, rather than direct release to the
atmosphere
© 2012 Pearson Education, Inc.
Energy Policy for the Future
• Hard path: Continuing “business as usual”
– Environmental problems due to use of local
resources, and industrialization and technology
bringing solutions to the problems
– Dominate energy planning in the United States
• Soft path: Emphasis on energy alternatives
– Renewable, flexible, decentralized, and
environmentally more benign than those of the
hard path
© 2012 Pearson Education, Inc.
Sustainable Energy Policy
• Energy planning for the future is complicated
• Necessary to find useful long-term sources of
energy without causing atmospheric pollution
• Transition from the hard to soft path involving
continued use of fossil fuel
• Energy path: Satisfying modern society needs
without endangering the planet
© 2012 Pearson Education, Inc.
Critical Thinking Topics
• Sustainable energy development means an energy
policy and energy sources without harming the
environment. Do you think this is possible?
• Is it possible that new technology will be able to
make fossil-fuel burning a clean process? Explain
• Speculate the possibility of power plants in space
• List specific actions that an individual citizen can
take to conserve energy and reduce environmental
impact
© 2012 Pearson Education, Inc.
End of Chapter 16
Chapter 1
Philosophy and Fundamental Concepts
Dr. Joao Santos
Chapter 1
Philosophy and Fundamental Concepts
Dr. Joao Santos
© 2012 Pearson Education, Inc.
What is Environmental Geology? (1)
• Geology is the science of processes related to the
composition, structure, and history of Earth and its life.
Geology is an interdisciplinary science, relying on aspects of
chemistry (composition of Earth’s materials), physics
(natural laws), and biology (understanding of life forms).
• Environmental Geology is applied geology. Specifically, it
is the use of geologic knowledge to help society solve
conflicts in land use, to minimize environmental degradation,
and to maximize the beneficial results of using our natural
and modified environments.
© 2012 Pearson Education, Inc.
What is Environmental Geology? (2)
The application of geology to these problems includes the
study of the following:
• Earth materials, such as minerals, rocks, and soils, to
determine how they form, their potential use as resources or
waste disposal sites, and their effects on human health.
• Natural hazards, such as floods, landslides, earthquakes,
and volcanic activity, in order to minimize loss of life and
property.
• Land for site selection, land-use planning, and
environmental impact analysis.
© 2012 Pearson Education, Inc.
What is Environmental Geology? (3)
• Hydrological processes of groundwater and surface water to
evaluate water resources and water pollution problems.
• Geological processes, such as deposition of sediments on
the ocean floor, the formation of mountains, and the
movement of water on and below the surface of Earth, to
evaluate local, regional, and global change.
© 2012 Pearson Education, Inc.
Earth History (1)
• Inception: 4.6 billion yrs
© 2012 Pearson Education, Inc.
Our Solar System (1)
Solar
flare
•
Solar System Formation: Nebular theory
– Planets formed ~ 4.6 billion years ago
– Solar system condensed from a solar nebula
(usually remnants of a supernova)
• Because of gravity most material collected
at center as the hot protosun.
• Other material formed a flattened rotating
disc.
– Matter in the disc cooled and collided forming
planetesimals
© 2012 Pearson Education, Inc.
Our Solar System (2)
Solar
flare
Solar System Formation: Nebular theory
• As the protoplanets formed, the materials that compose them separated.
– Dense metallic elements (iron and nickel) sank toward their centers
forming their cores
– Lighter elements (silicate minerals, oxygen, hydrogen) migrated
toward their surfaces forming their mantles and crusts
– Process called chemical differentiation
• Due to their surface gravities (a consequence of their mass), Venus and
Earth retained atmospheric gases forming considerable atmospheres.
• Due to frigid temperatures in the outer solar system, the Jovian planets
collected ice around their cores. As their cores grew, their surface gravity
increased allowing them to collect large amounts of gas (hydrogen and
helium) that were available in the outer solar system.
© 2012 Pearson Education, Inc.
Our Solar System (3)
Solar System Formation: Nebular theory
• When stars form they are surrounded by a rotating disk of
cosmic debris (Nebular theory).
• Gravity pulls debris together to form planets that revolve
in a consistent direction around star.
− Heavier, rocky planets form closer to the star
− Lighter, gas-rich planets form farther from the star
• Potentially thousands or millions of extra-solar planets
revolve around other stars.
© 2012 Pearson Education, Inc.
Our Solar System (4)
© 2012 Pearson Education, Inc.
Earth History (2)
© 2012 Pearson Education, Inc.
Fundamental Concepts of Environmental Geology
• Five fundamental concepts
– Population growth
– Sustainability
– System and change
– Hazardous Earth processes
– Scientific knowledge and values
• Other important concepts in environmental
geology
– Finite resources, obligation to future
© 2012 Pearson Education, Inc.
Human Population Growth (1)
• Number one environmental problem: Nearly 7
billion by the year 2010
• “Population bomb?” Exponential growth
• Exponential growth
– Growth rate (G): Measured as a percentage
– Doubling time (D): D = 70/G
• Above Earth’s comfortable carrying capacity:
Use more resources, need more land space,
generate more waste
• Earth as the only suitable habitat in the
foreseeable future
© 2012 Pearson Education, Inc.
Human Population Growth (2)
• Population Bomb: About to Explode?
© 2012 Pearson Education, Inc.
Human Population Growth (3)
© 2012 Pearson Education, Inc.
Human Population Growth (4)
© 2012 Pearson Education, Inc.
Human Population Growth (5)
© 2012 Pearson Education, Inc.
Human Population Growth (6)
Uneven growing pace and distribution
• By 2050, 3 billions more people
• Almost all of the growth in developing countries
• No easy answer to the population problems
• Education is paramount, especially woman’s
education. As people become more educated,
the population growth rate tends to decrease
• Good news: The rate of population growth is
decreasing
© 2012 Pearson Education, Inc.
Sustainability (1)
Sustainability: The environmental objective
• An evolving concept
• Expectation and reality
• Criteria variations in space and over time
• Is a long-term concept and has long-term
implications
• Requiring careful resources allocation, large-
scale development of new technology for
resource use, recycling, and waste disposal
© 2012 Pearson Education, Inc.
Sustainability (2)
Measuring sustainability
• Use and consumption of non-renewable
resources
• Natural replenishment and renewable rates
• Global consumption versus replenishment of
resources
• Development and improvement of human
environment versus viable environment
• Not lead to environmental crisis
© 2012 Pearson Education, Inc.
Sustainability: The Death of Aral Sea (3)
• Once a prosperous vacation spot in 1960
• Water diversion for agriculture
• Dying sea surrounded by salt flats
• Largely irreversible
© 2012 Pearson Education, Inc.
Sustainability: The Death of Aral Sea (4)
© 2012 Pearson Education, Inc.
Earth’s Systems and Changes (1)
• System conditions: Open versus closed systems
• System input-output analysis
• System changes: Types of changes, rates of
changes, scales of changes, etc.
• Rates of change: Average residence time
– T = S/F
(T: residence time, S: total size of stock, F: average rate of
transfer)
© 2012 Pearson Education, Inc.
Earth’s Systems and Changes (2)
© 2012 Pearson Education, Inc.
Earth’s Systems and Changes (3)
• Earth: A dynamic system
• Four interconnected subsystems: Lithosphere,
atmosphere, hydrosphere, and biosphere
• Four subsystems are interconnected and
interdependent
• Present human activity key to understanding the
future
© 2012 Pearson Education, Inc.
Predicting Future Changes
• Uniformitarianism (James Hutton, 1785)
– The present is the key to the past
– The present is the key to the future
– Changes of frequency and magnitude:
Geological processes and human activities
• Environmental unity: Chain of actions and reactions
• Earth system
– Gaia hypothesis: Earth is a living organism
– Complex and interrelated subsystems
– Global perspective on environment
© 2012 Pearson Education, Inc.
Hazardous Earth Processes
Hazardous Earth processes and risk statistics for
the past two decades
• Annual loss of life: About 150,000
• Financial loss: > $20 billion
• Millions of life loss during the past 20 years,
particularly catastrophic from a major natural
disaster in a developing country (2003 Iran
quake, ~30,000 people, 2004 Asia tsunamis,
~300,000)
• More property damage occurs in a more
developed country
© 2012 Pearson Education, Inc.
Scientific Knowledge and Values (1)
• Science: Accumulated knowledge
• Knowledge: Basis for decision making
• Scientific methods: Formulate possible solutions
to environmental problems
• Scientific design: Structure more suitable for
certain environmental settings
• Scientific info: Public awareness and
environmental regulations
© 2012 Pearson Education, Inc.
Scientific Knowledge and Values (2)
© 2012 Pearson Education, Inc.
Solving Environmental Problems
• Difficult processes
• Environmental problems tend to be complex
• Rapid changes, slow recognition, slower actions
• Some changes are of irreversible nature
• Environmental policy links to environmental
economics in infancy
© 2012 Pearson Education, Inc.
End of Chapter 1
Chapter 10
Slope Processes, Landslides,
and Subsidence
Dr. Joao Santos
Chapter 10
Slope Processes, Landslides,
and Subsidence
Dr. Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Introduction to Mass Movements
� Most humans consider Earth
to be “terra firma.”
� Earth’s surface, however, is
mostly unstable ground.
� This is a consequence of
weathering and erosion.
� We may be reminded of this
instability without warning.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Mass Movements
� Downslope motion of earth materials by gravity.
� Mass movements are a type of natural hazard.
� Natural feature of the environment.
� Can cause damage to living things and buildings.
� These hazards can produce catastrophic losses.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Mass Movements
� Mass movements are important to the rock cycle.
� The initial step in sediment transportation.
� A significant agent of landscape change.
� All slopes are unstable; they change continuously.
� Mass movement is often aided by human activity.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Classification based upon four factors:
� Type of material (rock, regolith, snow, or ice).
� Rate of movement (fast, intermediate, or slow).
� Nature of moving mass (cloud, slurry, or distinct blocks).
� Surroundings (subaerial or submarine).
� Can cause damage to living things and buildings.
� These hazards can produce catastrophic losses.
� All slopes are unstable; they change continuously.
� Mass movement is often aided by human activity.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Creep – Slow downhill movement of regolith.
� Due to expansion and contraction.
�Wetting and drying.
�Freezing and thawing.
� Grains are moved…
�Perpendicular to slope upon expansion.
�Vertically by gravity upon contraction.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Creep initiates tilt of trees, gravestones, and walls.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Solifluction – Slow downhill movement of tundra.
� Melted permafrost slowly flows over deeper frozen soil.
� This process generates hillsides with solifluction lobes.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Slumping – Sliding of regolith as coherent blocks.
� Slippage occurs along a spoon-shaped “failure surface.”
� Display a variety of sizes and rates of motion.
� Have distinctive features…
�Head scarp.
�Bulging toe.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Mudflows and debris flows – H2O-rich movement.
� Mudflow – A slurry of water and fine sediment.
� Debris flow – A mudflow with many large rocks.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Lahar – A special volcanic mud or debris flow.
� Volcanic ash (recent or ongoing eruptions) mixes with…
� Water from heavy rains or melted glacial ice.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Landslides – Movement down a non-vertical slope.
� Rock slide – A slide consisting of rock only.
� Debris slide – A slide comprised mostly of regolith.
� Movement down the failure surface is sudden and deadly.
� Slide debris can move at 300 km/hour on a cushion of air.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Landslide Case Study
� The Vaiont Dam disaster – Illustrates the need to evaluate
underlying geology when developing critical structures.
� Built in 1960 in a deep synclinal gorge in the Italian Alps.
� Limestone over shale dipped toward the valley center.
� On 10/9/63, 600 million tons of limestone fell into the reservoir.
� A wave crested the dam, destroyed villages, and killed 2,600.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Avalanches – Turbulent clouds of debris and air.
� Snow avalanche – Oversteepened snow that detaches.
� Debris avalanche – Rock and dust fragments.
� Move up to 250 km/hr on a cushioning layer of air.
� Reoccur in defined chutes; destroy stationary objects.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Rockfalls and debris falls – Vertical freefall of rock mass.
� Bedrock or regolith falls rapidly downward.
� When blocks impact, they fragment and continue moving.
� Talus blocks pile up at the base of the slope.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Types of Mass Wasting
� Submarine mass movements – Slides under ocean
water.
� Enormous volumes of material are moved downslope.
� Large slides alter the sea floor bathymetry.
� These movements trigger gigantic tsunami waves.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Why Mass Movement?
� Mass movements require that earth materials…
� Be subjected to topographic (slope) forces.
� Be weakened or loosened from their attachments.
� Fragmentation and weathering.
� The upper crust is broken by jointing and faulting.
� Chemical and physical
weathering produces regolith.
� Surface material is much
weaker than solid crustal rock.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Weakening the Surface
� Slopes may be stable or unstable.
� Slope stability is a dynamic balance between two forces.
� Downslope force – Gravitational pull.
� Resisting force – Material properties that repel motion.
� Movement occurs
when downslope
forces prevail.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
� Downslope forces = Gravity.
� The weight of earth materials.
� The weight of added water.
� The weight of added structures.
� Resisting forces = Material strength.
� Cohesion.
�Chemical bonds.
�Electrical charges.
�Surface tension.
� Friction.
� Steeper slopes = larger forces.
Slope Stability
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Slope Stability
� Loose granular material assumes a slope angle.
� “Angle of repose” is a material property due to…
� Particle size and shape and the surface roughness.
� Typical angles of repose.
� Fine Sand 35o
� Coarse Sand 40o
� Angular Pebbles 45o
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Failure Surfaces
� Weak subsurface layers can initiate motion.
� Types of “failure surfaces” include…
� Saturated sand or clay layers.
� Joints parallel to the land surface.
� Weak sedimentary bedding (shale, evaporites).
� Metamorphic foliation.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Failure Triggers
� A triggering event is not necessary for movement.
� Slope materials weaken over time.
� Gravity continues to operate.
� Mass movements are often random and unpredictable.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Failure Triggers
� Shocks, vibrations, and liquefaction.
� Ground vibrations decrease material friction.
� On an unstable slope, the downslope force takes over.
� Vibrations are common.
�Motion of heavy machinery or trains.
�Earthquakes.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Failure Triggers
� Changes in characteristics can destabilize a slope.
� Angle – Steepening a slope beyond the angle of repose.
� Loading – Adding weight to the top of a slope.
�Water – As rain or via humans (lawns, septic systems).
�Waste materials and fill.
�Buildings.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Failure Triggers
� Changes in characteristics can destabilize a slope.
� Removing support – Undercutting a slope leads to failure.
�Natural – River eroding the base of a slope.
�Human-induced – Excavating the base of a slope.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Failure Triggers
� Changes in slope strength.
� Weathering – Creates weaker regolith.
� Vegetation – Stabilizes slopes. Removing vegetation…
�Greatly slows removal of excess water.
�Destroys an effective stapling mechanism (roots).
�Slope failures common after forest fires destroy vegetation.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Failure Triggers
� Changes in slope strength.
� Water – Reduces slope strength in several ways.
�Adds a great deal of weight .
�Water in pores pushes grains apart, easing disintegration.
�Water lubricates grain contacts.
� Removing water, thereby, strengthens a failure surface.
Edited by Joao Santos
© 2012 Pearson Education, Inc.
End of Chapter 10
Chapter 13
Water Resources
Dr. Joao Santos
Chapter 13
Water Resources
Dr. Joao Santos
© 2012 Pearson Education, Inc.
Case History: Long Island
•
Groundwater
pollution: A serious problem on the
western end of the island since the beginning of
twentieth century
• Groundwater is the sole water supply for the Nassau
and Suffolk counties, 3 million people
• Groundwater below Nassau County is tremendous, yet
intensive pumping causing as much as 15 m decline in
water level
• Salt-water intrusion due to declination in water level
• Urbanization triggered more serious water pollution:
Urban runoff, sewage and fertilizers, road salt,
industrial and other wastes, and landfills (most of them
have been closed)
© 2012 Pearson Education, Inc.
Case History: Long Island
© 2012 Pearson Education, Inc.
Case History: Long Island
© 2012 Pearson Education, Inc.
Water: A Global Perspective
• Cyclic nature
– Global movement of water between different water
storage compartments
• Global distribution
– Abundance not a problem
– Distribution in space and over time a problem
– Supply versus use a problem
– More than 99 percent of Earth’s water is unavailable
or unsuitable for beneficial human use (salt and ice),
all people compete for less than 1 percent of Earth’s
water supply
© 2012 Pearson Education, Inc.
Global Water Cycle
• Water’s vertical movement
– Upflow: Evaporation, transpiration
– Downflow: Precipitation and infiltration
• Water’s horizontal movement
– Surface runoff
– Shallow subsurface through flow
– Groundwater flow
© 2012 Pearson Education, Inc.
Global Water Cycle
© 2012 Pearson Education, Inc.
Global Water Supply
© 2012 Pearson Education, Inc.
Surface Water (1)
Surface runoff: Important effects on both the
transportation and erosion
• Drainage network
• Drainage basin or watershed: An area of land
that contributes water to a particular stream or
river, a basic unit of landscape
• Drainage divide: The boundary between
drainage basins
• Stream order and size of drainage basin
© 2012 Pearson Education, Inc.
Surface Water (2)
© 2012 Pearson Education, Inc.
Surface Water (3)
© 2012 Pearson Education, Inc.
Surface Water (4)
Factors affecting runoff and sediment yield
• Geological factors: Type and structure of soils
and rocks
• Topographic factors: Relief and slope gradient
• Climatic factors: Type, intensity, duration, and
distribution of precipitation
• Vegetation factors: Type, size, and distribution
• Land-use practice factors
© 2012 Pearson Education, Inc.
Surface Water (5)
© 2012 Pearson Education, Inc.
Groundwater (1)
Groundwater (GW) profile
• Vadose zone (unsaturated zone, zone of
aeration)
• Zone of saturation
• Water table: The boundary of the above two
zones
• Perched water table: Local water table above a
regional water table
© 2012 Pearson Education, Inc.
Groundwater (2)
© 2012 Pearson Education, Inc.
Groundwater (3)
• Aquifer: A unit capable of supplying water at an
economically useful rate
• Aquitard or aquiclude: A confining layer or unit
restricting and retarding groundwater flow
• Unconfined aquifer: No overlying confining layer
• Confining aquifer: With an overlying aquitard
layer
• Perched aquifer: Local zone of saturation above
a regional water table
© 2012 Pearson Education, Inc.
Groundwater (4)
© 2012 Pearson Education, Inc.
Groundwater (5)
Groundwater recharge and discharge
• Recharge zone: Area where water infiltrates
downward from surface to groundwater
• Discharge zone: Area where groundwater is
removed from an aquifer, such as spring, well,
river, etc.
• Influent stream: Above the water table, recharge
water to groundwater, may be intermittent
• Effluent stream: Perennial stream with the
addition of groundwater when precipitation is
low
© 2012 Pearson Education, Inc.
Groundwater (6)
• Groundwater pressure surface: Generally
declining from source along the flow from
recharge area to discharge area
• Artesian well: Water self-rising above the land
surface in a confined aquifer
• Cone of depression: Drawdown cone of
groundwater in a well
© 2012 Pearson Education, Inc.
Groundwater (7)
© 2012 Pearson Education, Inc.
Groundwater Movement (1)
• Hydraulic gradient: The gradient of water table,
generally following the topographic gradient
• Hydraulic conductivity: Ability of rock materials
to allow water to move through (m3/day/m2)
• Porosity: Percentage of void (empty) space in
sediment or rock to store water
• Permeability: Measuring the interconnection of
pores in a rock material
© 2012 Pearson Education, Inc.
Groundwater Movement (2)
© 2012 Pearson Education, Inc.
Groundwater Use and Supply (1)
• Available groundwater estimated above the total
flow of the Mississippi during the last 200 years
• Groundwater as primary drinking water source
for ~50 percent of the U.S. population
• Groundwater overdraft problems (extraction rate
exceeding recharging rate) in many parts of the
country, particularly some states in the Great
Plains region
• Estimated 5 percent of groundwater depleted,
but water level declined more than 15 m (50 ft)
in some areas
© 2012 Pearson Education, Inc.
Groundwater Use and Supply (2)
© 2012 Pearson Education, Inc.
Groundwater Use and Supply (3)
© 2012 Pearson Education, Inc.
Groundwater Use and Supply (4)
© 2012 Pearson Education, Inc.
Interactions Between Surface Water and
Groundwater
• Overdraft of groundwater : Leads to lower water
levels of streams, lakes, reservoirs, etc.
• Overuse of surface water: Yields lower discharge
rates of groundwater
• Effluent stream (in groundwater discharge zone):
Tends to be perennial
• Influent stream (in groundwater recharge zone
above the water table): Often intermittent or
ephemeral
• Special linkage area: Sinkholes and cavern systems
in the karst terrains
© 2012 Pearson Education, Inc.
Interactions Between Surface Water and
Groundwater
© 2012 Pearson Education, Inc.
Karst Topography Problems
• Water pollution occurs where sinkholes have been
used for waste disposal.
• Cavern systems are prone to collapse, producing
sinkholes that may form in areas that damage
buildings on the ground surface, roads, and other
facilities
• In many areas underlain by limestone, such as the
Edwards Plateau in Texas, groundwater is being
mined. As a result of the mining, important karst
springs where water emerges from caverns are
being changed, causing a reduction in biodiversity
© 2012 Pearson Education, Inc.
Karst Topography Problems
© 2012 Pearson Education, Inc.
Karst Topography Problems
© 2012 Pearson Education, Inc.
The Edwards Aquifer
• Mark Twain “Whisky is for drinking and water is for
fighting over.” Intense conflict over water in central TX
• One of the most prolific in N. America, providing water for
more than 2 million people, with a natural yield of 25,000
gallons per minute
• Recharged primarily through influent streams flowing over
the recharge zone where water sinks into the limestone
• Increased water demand for growing urban areas and for
irrigation
• Ecosystems dependent upon the spring water: the San
Marcos spring salamander, the fountain darter fish, and
Texas wild rice are endangered species
© 2012 Pearson Education, Inc.
The Edwards Aquifer
© 2012 Pearson Education, Inc.
Water Use (1)
• Offstream use: Removal or diversion from its
surface water or groundwater sources
temporarily (e.g., irrigation, thermoelectric,
industrial use)
• Consumptive use: Type of offstream use of
water without intermediate return to the surface
water or groundwater, such as transpiration and
human use
• Instream use: Navigation, fish and wildlife,
recreational uses
© 2012 Pearson Education, Inc.
Water Use (2)
© 2012 Pearson Education, Inc.
Water Use (3)
In major urban areas
• Over withdrawal of groundwater
• Overuse of local surface water
• Threats of local urban landfills to the water
supply (e.g., Long Island, NY)
• Water import issues and problems: What is
distance to transport? How much water
available? From where? Conflicts with other
areas, litigations, and long-range planning
© 2012 Pearson Education, Inc.
Water Use (4)
© 2012 Pearson Education, Inc.
Trends in Water Use (1)
Based on the data from 1950–1995
• Surface water use far greater than groundwater
use
• The rate of water use decreased and leveled off
since 1980
• Irrigation and thermoelectric are major fresh
consumptive water use
• Less fresh water use since 1980 due to new
tech and water recycling
© 2012 Pearson Education, Inc.
Trends in Water Use (2)
© 2012 Pearson Education, Inc.
Trends in Water Use (3)
© 2012 Pearson Education, Inc.
Water Conservation
• Improved agricultural irrigation could reduce water
withdrawals by between 20 percent and 30 percent
• Engineering technology and structure (canals):
Regulating irrigation and reducing evaporation
• Better technologies in power plants and other
industries: Less use of water due to improved
efficiency
• Domestic use of water (urban and rural) accounts for
only 10 percent of the total national withdrawals, can
be reduced at a relatively small cost with more
efficient bathroom and sink fixtures
• Global water conservation: Virtual water budgets
© 2012 Pearson Education, Inc.
Conservation of Water at the
Global Scale
© 2012 Pearson Education, Inc.
Water Management (1)
Needs for water management
• Increasing demand for water use (population
and economic development)
• Water supply problems in semiarid and arid
regions
• Water supply problems in mega cities of humid
regions
• Water traded as a commodity: Capital, market,
and regulations?
© 2012 Pearson Education, Inc.
Water Management (2)
Aspects to be considered: Leopold philosophy
• Natural environmental factors: Geologic,
geographic, and climatic
• Human environmental factors: Economic, social,
and political
• Strategies
– More surface water use in wet years, more
groundwater use in dry years
– Reuse and recycle water regular basis as well as
emergencies
© 2012 Pearson Education, Inc.
Management of the Colorado River (1)
Managing the water
• Water appropriation to seven states in the
United States and to Mexico
• Local needs versus regional needs (Colorado
River compact of 1922)
• The United States versus Mexico (Treaty with
Mexico in 1944)
• Human use versus needs of lands (1974
Salinity Control Act)
© 2012 Pearson Education, Inc.
Management of the Colorado River (2)
© 2012 Pearson Education, Inc.
Management of the Colorado River (3)
Managing the river
• Dam construction
• Impact on flood frequency
• Impact on sediment distribution, particularly
downstream
• Impact on wildlife habitats
• Controlled and planned floods
© 2012 Pearson Education, Inc.
Water and Ecosystems
• Ecosystems: Changes in response to climate, nutrient
input, soils, and hydrology
• General tendency: Increased human use of water,
increased degradation of natural ecosystems
• Overall reconciliation between multiple water uses
– Water resources development (dam, reservoirs, canals) and
associated impact on surface water environment
– Reconciling the uses of water: Agriculture, industry,
urbanization, and recreation
– Protection of wetland and water resources
© 2012 Pearson Education, Inc.
Wetlands and Ecosystems
Wetlands: swamps, marshes, bogs, prairie potholes, vernal pools
• Wetlands are one of nature’s natural filters. Plants in wetlands
may effectively trap sediment, nutrients, and pollutants
• Freshwater wetlands are a natural sponge. During floods, they
store water, helping to reduce downstream flooding and
release water after the flood, nourishing low flows of river
systems
• Wetlands are highly productive lands where many nutrients
and chemicals are naturally cycled while providing habitat for a
wide variety of plants and animals
• Freshwater wetlands are often areas of groundwater recharge
to aquifers. Some of them, a spring-fed marsh, for example,
are points of groundwater discharge
© 2012 Pearson Education, Inc.
Emerging Global Water Shortage
• Isolated shortage of water: Indication of a global
pattern of water shortage
• Depleted water resources: Over-drafted aquifers,
dried lakes (Aral Sea), troubled streams (Colorado
and Yellow River not reaching seas some years)
• Polluted limited water resources due to
development and increased wastes
• Demands for water resources tripled as populated
more doubled last 50 yrs and growing fast next
50 yrs
• Global warming: Causing more problems
© 2012 Pearson Education, Inc.
End of Chapter 13
Chapter 14
Water Pollution
Dr. Joao Santos
Chapter 14
Water Pollution
Dr. Joao Santos
© 2012 Pearson Education, Inc.
Case History: NC Bay of Pigs
(1)
• Hurricane Floyd through NC in Sept 1999, forcing 48,000
people into shelters and killing 50 people
• Estimated 30,000 hogs, 2 million chickens, and 735,000
turkeys died
• Catastrophic water pollution as a result of the floodwater
from Hurricane Floyd
• More than 38 pig waste lagoons washed out, 250 million
gallons of pig wastes into creeks, rivers, and wetlands
• North Carolina has a long history of hog production, the
population of pigs swelled from about 2 million in 1990 to
over 10 million by 1997. Approximately 250 pig operations
flooded out
• Polluted water through schools, churches, homes, and
businesses
© 2012 Pearson Education, Inc.
Case History: NC Bay of Pigs
© 2012 Pearson Education, Inc.
Case History: NC Bay of Pigs
© 2012 Pearson Education, Inc.
Case History: NC Bay of Pigs (2)
• In 1997, a state law was enacted that prohibited
building new waste lagoons and sewage plants on
floodplains
• In the spring of 1999, the governor proposed a
10-year plan that would phase out the state’s 4,000
animal waste lagoons
• Hurricane Floyd occurred before these changes could
be enacted
• In 2007, the state passed legislation to ban
construction or expansion of new lagoons and
spray fields
• On-site treatment facilities to replace swine lagoons
© 2012 Pearson Education, Inc.
Water Pollution
• Water pollution: Refers to degradation of water
quality as measured by biological, chemical, or
physical criteria
• Pollutants: Any substance that, in excess, is known
to be harmful to desirable living organisms
• The greatest water pollution problem in the world
today is lack of disease-free drinking water for
about 20 percent of the world’s population
• Waterborne diseases that kill about 2 million people
a year, and most of the deaths are of children under
the age of 5
© 2012 Pearson Education, Inc.
Common Pollutants
(1)
• Oxygen-demanding waste (common organic
waste)
• Pathogenic waste (pathogenic microbes)
• Nutrients
• Petroleum (oil)
• Toxic waste (chemicals, heavy metals,
radioactive waste)
• Sediment
• Thermal plumes
© 2012 Pearson Education, Inc.
Common Pollutants (2)
• Oxygen-demanding waste
– Dead organic matter decomposed by bacteria, an
oxygen-demanding process
– BOD: High BOD associated with a high level of
decaying organic matter in water, reducing DO
(dissolved O) for other healthy organisms
– Sources of oxygen-demanding waste: Natural
processes, agricultural applications, urban sewage,
and runoff
© 2012 Pearson Education, Inc.
Common Pollutants (3)
• Pathogenic microbes
– Fecal coliform bacteria
– Harmful risks (diseases and death ) of E. coli
– Billions exposed to waterborne diseases, especially
in poor countries
– Outbreaks do occur in developed countries (e.g.,
GA’s water park in 1998; Walkerton public water
supply, Ontario in 2000; CA spinach contamination in
2006)
– Epidemic risks of waterborne diseases during natural
disasters, such as earthquake, tsunami, flooding
© 2012 Pearson Education, Inc.
Common Pollutants (4)
• Nutrients
– Two important nutrients: N, P
– Major problems: Cultural eutrophication — algae
bloom, triggering BOD problem
– Major sources for nutrients: Fertilizer, feedlots, and
discharge from wastewater treatment plants
– Areas of certain land use: Agriculture and urban
© 2012 Pearson Education, Inc.
Common Pollutants (5)
• Oil
– Major problems: Polluted water, ecosystem damage,
interrupted socioeconomic conditions of a
community
– Major sources: Oil spills from tankers and pipelines,
on- or off-shore oil production, war (e.g., the Gulf
war, 2006 war in Lebanon)
© 2012 Pearson Education, Inc.
Common Pollutants
© 2012 Pearson Education, Inc.
Common Pollutants (6)
• Toxic waste
– Synthetic organic chemicals, up to 100,000
chemicals in use, especially those POPs (persistent
organic pollutants)
– Heavy Metals: Pb, Hg, Zn, Cd (e.g., lead
contamination)
– Radioactive materials
© 2012 Pearson Education, Inc.
Common Pollutants (7)
• Sediment pollution
– Sand and smaller particles
– Polluted streams, lakes, reservoirs, even ocean
water
– Major sources: Soil erosion, dust storms, floods, and
mudflows
– Greatest water pollutant by volume
© 2012 Pearson Education, Inc.
Common Pollutants (8)
• Thermal pollution
– Temp increases, less dissolved oxygen
– Adverse changes to the habitats of organisms
– Economic impacts
– Major sources: Hot-water discharge from industrial
operations, power plants, abnormal ocean currents
© 2012 Pearson Education, Inc.
Surface Water Pollution and Treatment (1)
Point sources of pollution
• Point sources are discrete, confined, and more
readily identifiable
• Common sources: Landfills, discharge from
wastewater treatment plants, discharge from
industries, power plants, storm water runoff, etc.
• Identify sources, on-site treatment and
mitigation, prevention
© 2012 Pearson Education, Inc.
Surface Water Pollution and Treatment (2)
• Nonpoint sources of pollution: Influenced by
such factors as land use, climate, hydrology,
topography, native vegetation, and geology
– Nonpoint sources are diffused, intermittent, and hard
to specifically identify
– Causes of nonpoint pollutions often regional,
cumulative and compound
– Influenced by land use, climate, hydrology,
topography, and geology
– Common sources: Urban runoff, agricultural, mining
(acid rain and acid drainage)
© 2012 Pearson Education, Inc.
Acid Mine Drainage
• Acid mine drainage: refers to acidic water with
elevated concentrations of dissolved metals that
drains from coal or metal mines
• Acid mine drainage is water with a high concentration
of sulfuric acid (H2SO4)
• Acid mine drainage is produced by complex
geochemical and microbial reactions
• The acid water is extremely toxic to plants and
animals in aquatic ecosystems
• The Tar Creek area in Oklahoma was at one time
designated by the EPA as the nation’s worst example
of acid mine drainage
© 2012 Pearson Education, Inc.
Acid Mine Drainage
© 2012 Pearson Education, Inc.
Groundwater Pollution (1)
• Why care about ground water pollution?
– Most abundant freshwater source
– Growing dependency on groundwater
– About 50 percent of people in United States depend
on groundwater for drinking water
– Triggers other environmental problems: Water
pollution, subsidence, saltwater intrusion, etc.
© 2012 Pearson Education, Inc.
Groundwater Pollution (2)
• It is estimated that 75 percent of the 175,000
known waste-disposal sites in the country may be
producing plumes, or bodies of contaminated
groundwater
• Groundwater pollution hazard impact depends on
– Amount of contaminant discharged
– Chemical concentration or toxicity
– Degree and duration of exposure of people or other
organisms to the pollution
© 2012 Pearson Education, Inc.
National Water-Quality Assessment
Program
• In the past 25 years, great improvements in manufacturing,
processing, and wastewater-treatment facilities
• The program integrates both surface-water and groundwater
systems that monitor and study aquatic ecosystems
• The goals of the program are to:
• Carefully describe current water-quality conditions for many
of the freshwater streams and aquifers
in the United States
• Monitor and describe water-quality changes over time
• Increase understanding concerning the human and natural
factors that affect the nation’s water quality
© 2012 Pearson Education, Inc.
Groundwater Pollution versus Surface
Water Pollution
• Residence time difference
• Environmental conditions: Inflow, flow rate,
dissolved oxygen, sunlight
• Harder to track pollution sources
• More difficult and expensive to clean up
• May pose long-term risks
© 2012 Pearson Education, Inc.
Infiltration of Urban, Industrial, and
Agricultural Runoff
The Delaware River basin: A large water systems under study
• Effects of the river system on the distribution, fate, and effects
of contaminants in water, sediment, and living things
• Relationships between the water flow in the river and
concentrations of nutrients, contaminants, and pathogens
• Presence of contaminants, including pathogens and pesticides,
in drinking water supplies and recreational activities
• Development of management plans and strategies for the
protection of river basin that have high water quality
• Effects of septic systems on water quality and river ecology
• Effects of groundwater withdrawals on water quality
• Effects of discharge from coal mines on water quality
© 2012 Pearson Education, Inc.
Water Quality and Stream Ecosystems
in the United States
© 2012 Pearson Education, Inc.
Saltwater Intrusion
• More than half of the world’s population lives in
or near the coastal zones
• Groundwater pollution from saltwater intrusion is
not a local isolated problem
• Causes major water supply problems in NY, FL,
CA
• Case History: Long Island
© 2012 Pearson Education, Inc.
Saltwater Intrusion Mechanism
• Water table is inclined toward the ocean
• Wedge of saltwater is inclined toward the land
• Over-pumping of groundwater
• Severe drawdown of groundwater causes
saltwater ascension
© 2012 Pearson Education, Inc.
Saltwater Intrusion
© 2012 Pearson Education, Inc.
Groundwater Treatment (1)
• Pretreatment studies
– Identify contaminants and their characteristics of
transport behavior
– Identify the characteristics of aquifer geology (factors
controlling groundwater flow—physical dimensions,
structure)
– Determine the hydrologic characteristics of polluted
aquifer(s)—flow direction, flow rates, discharge and
recharge conditions
– Select possible treatment strategies and methods
© 2012 Pearson Education, Inc.
Groundwater Treatment (2)
© 2012 Pearson Education, Inc.
Water Quality Standards
• MCLs—Maximum Contaminant Levels
• Permissible limits for 83 contaminants
• MCLGs—Maximum Contaminant Level Goals
– The maximum level at which no adverse health
effects from a lifelong exposure
• SMCLs—Nonenforceable limits for contaminants
that affects aesthetic qualities in drinking water
© 2012 Pearson Education, Inc.
Wastewater Treatment
• Law: Used wastewater must be treated
• Break the potential vicious cycle of wastewater
entering the general water cycle
• Tier treatment and reuse system
– Septic system—rural residential areas
– Water treatment plant for towns and urban cities
– Innovated ways for recycling and reclaiming
wastewater
– New technologies for innovative wastewater
treatment
© 2012 Pearson Education, Inc.
Septic Tank Sewage Disposal System
© 2012 Pearson Education, Inc.
Idealized Diagram for Wastewater
Treatment Plant
© 2012 Pearson Education, Inc.
Wetlands as WW-Treatment Sites
• Both natural and human-constructed wetlands:
good places to treat or partially treat wastewater
(WW)
• For communities with difficulty purchasing
expensive WW treatment plants or desire a
good alternative
• Warm-humid and hot-dry climates had
successful experiences
© 2012 Pearson Education, Inc.
WW Renovation and Conservation Cycle
© 2012 Pearson Education, Inc.
Federal Legislation
• The Clean Water Act of 1972 (amended in 1977)
• Survey after survey show strong public support for
a clean environment in the United States today
• The Water Quality Act of 1987 established national
policy to control nonpoint sources of water pollution
• In July 2000, President Clinton imposed new water
pollution controls, The plan will take at least 15
years to implement completely
© 2012 Pearson Education, Inc.
Reduce Effects of Water Pollution
• Develop and refine better ways to evaluate
water pollution problems and their impact on
aquatic life and the health of people
• Implement new and innovative, cost-effective
water treatment technologies
• Develop products and processes that minimize
production of water pollutants and their release
into the environment
© 2012 Pearson Education, Inc.
End of Chapter 14
Chapter 6
Earthquakes
Dr. Joao Santos
Chapter 6
Earthquakes
Dr. Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
What is an Earthquake?
� Earth shaking caused by a rapid release of energy.
� Due to tectonic stresses that cause rocks to break.
� Energy moves outward as an expanding sphere of waves.
� This waveform energy can be measured around the globe.
� Earthquakes destroy buildings and kill people.
� 3.5 million deaths in the last 2000 years.
� Earthquakes are common.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Seismicity
� Seismicity (earthquake activity) occurs due to…
� Motion along a newly formed crustal fracture (or fault).
� Motion on an existing fault.
� Inflation of a magma chamber.
� Volcanic eruption.
� Giant landslides.
� Meteorite impacts.
� Nuclear detonations.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Concepts
� Hypocenter (or focus) – The spot within the Earth where
earthquake waves originate.
� Usually occurs on a fault surface.
� Earthquake waves expand outward from the hypocenter.
� Epicenter – Land surface above the hypocenter.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Faults and Earthquakes
� Most earthquakes occur along faults.
� Common crustal fractures that move rock masses.
� The amount of movement is termed displacement.
� Displacement is also called offset, or slip.
� Markers reveal the
amount of offset.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
� Faults are like planar breaks in blocks of crust.
� Most faults slope (although some are vertical).
� On a sloping fault, crustal blocks are classified as:
� Footwall (block below the fault).
� Hanging wall (block above the fault).
Faults and Fault Motion
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Fault Types
� Fault type based on relative block motion.
� Normal fault
�Hanging wall moves down relative to footwall.
�Result from extension (stretching).
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Fault Types
� Fault type based on relative block motion.
� Reverse fault
�Hanging wall moves up relative to footwall.
�Results from compression (squeezing or shortening).
�Slope (dip) of fault is steep.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Fault Types
� Fault type based on relative block motion.
� Thrust fault
�Special kind of reverse fault.
�Slope (dip) of fault surface is not steep.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Fault Types
� Fault type based on relative block motion.
� Strike-slip fault
�Blocks slide laterally past one another.
�No vertical block motion.
�Fault surface is nearly vertical.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Fault Types
� Fault type based on relative block motion.
� Oblique-slip fault
�A combination of dip-slip and strike-slip displacement.
�Most faults display an oblique-slip character.
�Pure dip-slip or strike-slip faults are rare.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Fault Initiation
� Tectonic forces add stress to unbroken rocks.
� The rock deforms slightly (elastic strain).
� Continued stress will cause growth of cracks.
� Eventually, cracks grow to the point of failure.
� When the rock breaks, elastic strain transforms into brittle
deformation, releasing earthquake energy.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Fault Motion
� Faults move in jumps.
� Once movement starts, it quickly stops due to friction.
� Eventually, strain builds up again causing failure.
� This behavior is termed stick-slip behavior.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Seismic Waves
� Body waves – Pass through Earth’s interior.
� Compressional, or primary (P), waves
�Push-pull (compress and expand) motion.
�Travel through solids, liquids, and gases.
�Fastest.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Seismic Waves
� Body waves – Pass through Earth’s interior.
� Shear, or secondary (S), waves
�“Shaking” motion.
�Travel only through solids, not liquids.
�Slower.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Seismic Waves
� Surface Waves – Travel along Earth’s surface.
� Love waves – S waves intersecting the surface.
�Move back and forth like a writhing snake.
� Rayleigh waves – P waves intersecting the surface.
�Move like ripples on a pond.
� These waves are the slowest and most destructive.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Seismology
� Seismology is the study of earthquake waves.
� Seismographs – Instruments that record seismicity.
� Worldwide, they detect earthquakes anywhere on Earth.
� Seismology reveals size and location of earthquakes.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
� Measure wave arrivals and magnitude of motion.
� Straight line = background.
� 1st wave causes frame to sink (pen goes up).
� Next vibration causes opposite motion.
Seismographs
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Seismograph Operation
� Waves always arrive in sequence.
� P waves first
� S waves second
� Surface waves last.
� Wave arrivals are captured by the seismograph.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Locating an Epicenter
� p and s waves travel at different velocities.
� 1st arrivals of p and s waves vary with distance.
� A travel-time graph plots the distance of each station to
the epicenter.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Locating an Epicenter
� Data from 3 stations can pinpoint the epicenter.
� A circle is drawn around each station.
�The radius is equal to the distance to epicenter.
�Circles around 3 or more stations will intersect.
� The point of intersection is the epicenter.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Size
� Size is described by either intensity or magnitude.
� Mercalli intensity scale – Degree of shaking damage.
� Roman numerals assigned to different levels of damage.
� Damage occurs in zones.
� Damage diminishes in
intensity with distance.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Size
� Magnitude – The amount of energy released.
� Maximum seismogram motion.
� Several magnitude scales.
� Richter.
� Moment.
� Magnitude scales are
logarithmic.
� Increases of 1 unit = 10 fold
increase in ground motion.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Measuring Earthquake Size
� Earthquake energy release
can be calculated.
� M6.0 – Energy of the
Hiroshima bomb.
� M8.9 – Annual energy
released by all other
earthquakes.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Measuring Earthquake Size
� Small earthquakes are frequent.
� ~100,000 magnitude 3 / year.
� Large earthquakes are rare.
� 32 magnitude 7 earthquakes / year.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Occurrence
� Earthquakes linked to plate tectonic boundaries.
� Shallow – Divergent and transform boundaries.
� Intermediate and deep – Convergent boundaries.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Focal Depths
� Shallow – 0-20 km.
� Along the mid-ocean ridge.
� Transform boundaries.
� Shallow part of trenches.
� Continental crust.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Focal Depths
� Intermediate and deep earthquakes occur along the
subduction trace, the Benioff-Wadati zone.
� Intermediate – 20-300 km – Downgoing plate still brittle.
� Deep – 300-670 km – Mineral transformations?
� Earthquakes rare below
670 km (mantle is ductile).
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Convergent Boundaries
� Cities near subduction zones have frequent earthquakes.
� Most are minor.
� Periodically, they are devastating.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Continental Earthquakes
� Earthquakes in continental crust.
� Continental transform faults (San Andreas, Anatolian).
� Continental rifts (Basin and Range, East African Rift).
� Collision zones (Himalayas, Alps).
� Intraplate settings (ancient crustal weaknesses).
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
San Andreas Fault
� The Pacific plate meets the North American plate.
� The San Andreas is a very active strike-slip fault.
� A very dangerous fault; hundreds of earthquakes per year.
� San Francisco – Destroyed in 1906.
� Loma Prieta, 1989, World Series.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Earthquakes kill people and destroy cities.
� The damage can be heartbreaking and horrific.
� Knowledge improves odds of survival.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Ground Shaking and Displacement
� Earthquake waves arrive in a distinct sequence.
� Different waves cause different motion.
� P waves are the 1st to arrive.
� They produce a rapid up and down motion.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� S waves arrive next (2nd).
� They produce a pronounced back and forth motion.
� This motion is usually much stronger than from P-waves.
� S waves cause extensive damage.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Surface waves lag behind S waves.
� Love waves are the first to follow.
� Ground writhes like a snake.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� R waves are the last to arrive.
� The land surface behaves like ripples in a pond.
� These waves may last longer than others.
� Cause extensive damage.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Severity of shaking and damage depends on…
� Magnitude (energy) of the earthquake. More = more.
� Distance from the hypocenter.
� Intensity and duration of the vibrations.
� The nature of the subsurface material.
�Bedrock transmits waves quickly = less damage
�Sediments bounce waves = amplified damage.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Effects on buildings:
� Buildings “pancake.”
� Bridges topple.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Effects on buildings:
� Bridge supports crush.
� Masonry walls break apart.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Landslides and Avalanches.
� Shaking causes slopes to fail.
� Hazardous slopes bear evidence of ancient slope failures.
� Rockslides and avalanches follow earthquakes in uplands.
� Mount St. Helens erupted via an earthquake landslide.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Liquefaction – Waves liquefy H2O-filled sediments.
� High pore pressures force grains apart, reducing friction.
� Liquefied sediments flow as a slurry.
� Sand becomes “quicksand;” clay becomes “quickclay.”
�Sand dikes.
�Sand volcanoes.
�Contorted layering.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Liquefaction
� Water saturated sediments turn into a mobile fluid.
� Land will slump and flow.
� Buildings may founder and topple over intact.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Fire is a common hazard following earthquakes.
� Shaking topples stoves, candles, and power lines.
� Broken gas mains and fuel tanks ignite a conflagration.
� Earthquakes destroy critical infrastructure such as water,
sewer, telephone, and electrical lines, as well as roads.
� Firefighters powerless.
�No road access.
�No water.
�Too many hot spots.
� Good planning is
crucial to saving lives.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Earthquake devastation fuels disease outbreaks.
� Food, water, and medicines are scarce.
� Basic sanitation capabilities disabled.
� Hospitals damaged or destroyed.
� Health professionals overtaxed.
� There may be many decaying corpses.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Tsunamis, or seismic sea waves (not tidal waves).
� Tsunamis result when earthquakes change the seafloor.
� Normal faulting drops the seabed; thrusting raises it.
�This displaces the entire volume of overlying water.
�A giant mound (or trough) forms on the sea surface.
�This feature may be enormous (up to a 10,000 mi2 area).
�Feature collapse creates waves that race rapidly away.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Damage
� Destructive tsunamis occur frequently – about 1/yr.
� 94 destructive tsunamis in the last 100 years.
� 51,000 victims (not including 12/26/04)
� Future tsunami disasters are inevitable.
� Growing human population in low-lying coastal areas.
� Education about tsunamis can save many lives.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Tsunami vs. Wind Waves
� Wind waves
� Influence the upper ~100 m.
� Have wavelengths of several
tens to hundreds of meters.
� Wave height and wavelength
related to windspeed.
� Wave velocity maximum
several tens of km per hour.
� Waves break in shallow water
and expend all stored energy.
� Tsunami waves
� Influence entire water depth
� Have wavelengths of several
10s to 100s of kilometers.
� Wave height and wavelength
unaffected by windspeed.
� Wave velocity maximum
several 100s of kph.
� Waves come ashore as a
raised plateau of water that
pours onto the land.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Tsunami Behavior
� Tsunamis race at jetliner speed across the ocean.
� They may be almost imperceptible in deep water.
� Low wave height.
� Long wavelength.
� As water shallows, waves
slow from frictional drag.
� Waves grow in height,
reaching 10-15 m or more.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Tsunami
� Tsunami destruction of the coast depends upon…
� Offshore bathymetry.
�Broad shallows increase amplitude but sap wave energy.
�Quick deep-to-shallow transition – Deadliest condition.
�Waves have maximum energy.
�Wave heights are modest.
�Water pours onto land as a sheet.
� Topography of shore.
�Broad lowland – Maximum damage.
�Steep rise of land – Less damage.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Tsunami Reality
� The Indian Ocean Tsunami
� On December 26, 2004, a strong megathrust earthquake
(M9.0+) originated in the trench to the west of N. Sumatra.
� The earthquake was the largest in 40 years.
� Displacement exceeded 15 m; rupture > 1100 km long.
� The devastating tsunami killed people in 10 countries
surrounding the Indian Ocean.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
The Indian Ocean Tsunami
� Killed more people than any tsunami on record.
� 227,898 were killed or missing and presumed dead.
� 1.7 million people were displaced (as of 6/4/2009).
� Record-setting death toll.
� The earthquake was
so large and the
tsunami spread fast.
� Coasts were full of
Christmas tourists.
Source: USGS Earthquake Hazards Program, Most Destructive Earthquakes
http://earthquake.usgs.gov/regional/world/most_destructive.php/
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
The Indian Ocean Tsunami
� Complete devastation below “run-up” elevation.
� Dense coastal development in Banda Aceh hardest hit.
� Entire communities were erased – buildings and people.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Surviving a Tsunami
� Heed natural and official warnings.
� An earthquake in a coastal setting.
� Retreat of water from the shore is sign of an impending tsunami.
� Expect many waves.
� Bigger waves may be next.
� Wave arrival may last for hours.
� Abandon belongings.
� Get to high ground and stay there.
Source: Brian F. Atwater and others, 1999, Surviving a Tsunami – Lessons from Chile, Hawaii and Japan, USGS Circular 1187.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Surviving a Tsunami
� Expect roads to be impassable.
� Climb a sturdy building or a tree.
� Grab something that floats.
� Expect lots of debris (sediment, wreckage, corpses).
� Expect landscape changes.
Source: Brian F. Atwater and others, 1999, Surviving a Tsunami – Lessons from Chile, Hawaii and Japan, USGS Circular 1187.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Earthquake Prediction
� Prediction would help reduce catastrophic losses.
� Can we predict earthquakes? Yes and no.
� They CAN be predicted – long-term (tens to hundreds of
years).
� They CANNOT be predicted – short-term (hours to months).
� Seismic hazards are mapped to assess risk.
� This information is useful for…
� Developing building codes.
� Land-use planning.
� Disaster planning.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Long-Term Earthquake Prediction
� Probability of a certain magnitude earthquake occurring
on a timescale of 30 to 100 years, or more.
� Based on the premise that earthquakes are repetitive.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Long-Term Earthquake Prediction
� Require determination of seismic zones, by…
� Mapping historical epicenters (after ~ 1950).
� Evidence of ancient earthquakes (before seismographs).
�Evidence of seismicity – Fault scarps, sand volcanoes, etc.
�Historical records.
� Seismic gaps, places that haven’t slipped recently.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
Long-Term Earthquake Prediction
� Recurrence interval – Average time between events.
� Historical records.
� Geologic evidence – Requires radiometric dating of events.
�Sand volcanoes.
�Offset strata.
�Drowned forests.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: EarthquakesChapter 8: A Violent Pulse: Earthquakes
� Goal: The location and magnitude of a large earthquake.
� Currently, we can’t reliably predict short-range events.
� Earthquakes do have precursors.
� Clustered foreshocks.
� Crustal strain.
� Stress triggering.
� And, possibly…
�Water level changes in wells.
�Gases (Rn, He) in wells.
�Unusual animal behavior.
Short-Term Earthquake Prediction
Edited by Joao Santos
© 2012 Pearson Education, Inc.
End of Chapter 6
Chapter 8
Volcanic Activity
Dr. Joao Santos
Chapter 8
Volcanic Activity
Dr. Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 5: The Wrath of Vulcan: Volcanic EruptionsChapter 5: The Wrath of Vulcan:
Volcanic Eruptions
Volcanic Eruptions
� What is a volcano?
� An erupting vent through which molten rock surfaces.
� A mountain built from magmatic eruptions.
� Volcanoes are caused by tectonic activity.
� Volcanoes pose a number of hazards to humans.
� Mexico City.
� Seattle.
� Naples, Italy.
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� In 79 A.D. Mount Vesuvius erupted violently.
� Pyroclastic flows destroyed Pompeii, killing 20,000.
� A record of Roman life was preserved under ash.
Volcanic Eruptions
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Volcanic Eruptions
� Unpredictable, dangerous.
� Build large mountains.
� Blow mountains to bits.
� Eruptions can…
� Provide highly productive
soils to feed a civilization.
� Can extinguish a civilization
in a matter of minutes.
� Eruptions effect climate.
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Volcanic Materials
� The products of volcanic eruption take three forms:
� Lava flows – Molten rock that moves over the ground.
� Pyroclastic debris – Fragments blown out of a volcano.
� Volcanic gases – Vapor and aerosols that exit a volcano.
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Lava Flows
� Lava can be thin and runny or thick and sticky.
� Flow style depends on viscosity, which depends upon…
� Composition, especially silica (SiO2), Fe, and Mg content.
� Temperature.
� Gas content.
� Crystal content.
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Lava Compositions
� Lavas with high silica / low Fe and Mg are called…
� Silicic, felsic, or rhyolitic.
� Lavas with low silica / high Fe and Mg are called…
� Mafic or basaltic.
� Lavas with moderate silica, Fe, and Mg are called…
� Intermediate or andesitic.
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Basaltic Lava Flows
� Mafic lava – Very hot, low silica and low viscosity.
� Basalt flows are often thin and fluid.
� They can flow rapidly (up to 100 km/hr).
� They can flow for long distances (up to several 100 km).
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Basaltic Lava Flows
� Pahoehoe (pa-hoy-hoy) – a Hawaiian word describing
basalt with a glassy, ropy texture.
� Pahoehoe forms when extremely hot basalt forms a skin.
� With flow, the skin is rolled into ropy ridges and furrows.
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Basaltic Lava Flows
� A’a’ (ah-ah) is a Hawaiian word describing basalt that
solidifies with a jagged, sharp, angular texture.
� A’a’ forms when hot flowing basalt cools and thickens.
� With flow, lava crumbles into shards and fragments.
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Basaltic Lava Flows
� A cooled crust forms on top of a basalt flow.
� A conduit – a lava tube – develops in the flow.
� Tubes prevent cooling, facilitating flow for miles.
� Lava tubes become caves that can later transmit water.
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Basaltic Lava Flows
� Underwater, basalt cools instantly; it cannot flow.
� It cools to form a rounded blob called a pillow.
� The pillow surface is cracked, quenched glass.
� Lava pressure ruptures a pillow to form the next blob.
� The process repeats to form a mound of pillow basalts.
� Common on the mid-ocean ridge.
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Andesitic Lava Flows
� Higher SiO2 makes andesitic lavas viscous.
� Unlike basalt, they do not flow rapidly.
� Instead, they mound around the vent and flow slowly.
� The outer crust fractures, creating rubble.
� Andesitic lava flows remain close to the vent.
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Rhyolitic Lava Flows
� Rhyolite, with the highest SiO2, is the most viscous lava.
� Rhyolitic lava rarely flows.
� Rather, lava plugs the vent as a lava dome.
� Sometimes, lava domes are blown to smithereens.
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Basaltic Pyroclastic Debris
� Glass shards and fragmented lava in a range of sizes.
� Basaltic eruptions generate a lot of spatter.
� Lapilli – Pea to plum-sized material.
� Blocks and bombs – Apple to refrigerator-sized.
�Pele’s Hair – Strands of glass created by flying lava droplets.
�Bombs – Streamlined fragments of ejected lava.
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Explosive Pyroclastic Debris
� Intermediate and felsic magmas erupt explosively.
� More viscous than basaltic magma (from SiO2).
� Contain more gas.
� Produce large quantities of volcanic ash.
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Pyroclastic Flows
� Pyroclastic flows (or, nuee ardentes – French):A
� Avalanches of hot ash (200Co–450oC) that race downslope.
� Moving up to 300 kph, they Incinerate all in their path.
� Immediately deadly; they kill everything quickly.
� Many famous examples: Mt. Vesuvius, Mt. Pelee, and Mt.
Augustine.
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Pyroclastic Deposits
� Tephra – Deposits of pyroclastic debris of any size.
� Tuff – Lithified ash with or without lapilli.
� Air-fall tuff – Accumulations of ash that fell like snow.
� Ignimbrite (welded tuff) – Tuff that is deposited while hot.
�Hot pyroclastic flow material.
�Fuses together while cooling.
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Volcaniclastic Deposits
� Blocks – Preexisting rock fragmented by eruption.
� Blown out of a volcanic vent, blocks pile up nearby.
� Create unstable slopes that easily fail.
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Lahars
� Tephra is readily moved by water as a debris flow.
� Known as lahars, these flows are often deadly.
� Lahars move rapidly (up to 50 km per hour).
� They have the consistency of wet cement,.
� A distinct hazard to people living in volcanic valleys.
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Volcanic Gas
� Up to 9% of magma may be gas.
� Water (H2O) – Most abundant gas.
� Carbon dioxide (CO2) – Second in abundance.
� Sulfur dioxide (SO2) – Rotten egg smell.
� Magma composition controls gas content.
� Felsic magmas are gas-rich; mafic magmas are less so.
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Volcanic Gas
� Gases are expelled as magma rises.
� SO2 reacts with water to form aerosol sulfuric acid.
� Style of gas escape controls eruption violence.
� Low viscosity (basalt) – Easy escape; mellow eruption.
� High viscosity (rhyolite) – Difficult escape; violent eruption.
� Gas bubbles in rock are
called vesicles.
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Volcanic Architecture and Landforms
� Volcanoes have characteristic features.
� Magma chamber.
� Fissures and vents.
� Craters.
� Calderas.
� Distinctive profiles.
�Shield volcanoes.
�Cinder cones.
�Stratovolcanoes.
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Magma Chamber
� Located in the upper crust.
� Usually an open cavity or area of highly fractured rock.
� May contain a large quantity of magma.
� May inflate and deflate.
� Some magma cools here to form intrusive rock.
� Some magma may rise to the surface to form a volcano.
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Magma Release
� Some magma rises via a conduit to the surface.
� Magma may also erupt along a linear tear, a fissure.
� Fissure eruptions may display a “curtain of fire.”
� Fissures evolve into discrete vents.
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Craters
� Crater – A bowl-shaped depression atop a volcano.
� Craters are up to 500 m across; 200 m deep.
� Form as erupted lava piles up around the vent.
� Summit eruptions – Located within the summit crater.
� Flank eruption – Located along the side of a volcano.
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Caldera
Figure 4.1a
� A gigantic volcanic depression.
� One to ten kilometers across, larger than
a crater.
� Steep sidewalls and flat floors.
� Form from massive eruptions.
� The volcano collapses.
� Crater Lake, Oregon.
� Yellowstone National Park.
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Crater Lake Caldera, OregonCrater Lake Caldera, Oregon
CalderaCrater
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Volcano Types
� Shield volcanoes.
� Broad, slightly domed-shaped (like an inverted shield).
� Made by lateral flow of low-viscosity basaltic lava.
� Have a low slope and cover large geographic areas.
� Mauna Loa on Hawaii is a good example.
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Volcano Types
� Cinder cone – Conical piles of tephra.
� The smallest type of volcano.
� Built of ejected lapilli-sized fragments piled up at a vent.
� Slopes are at the angle of repose.
� Often symmetrical with a deep summit crater.
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Volcano Types
� Stratovolcanoes (Composite volcanoes).
� Large, cone-shaped volcano.
� Composed of alternating layers of lava and tephra.
� Often symmetric; can be odd shapes from landslides, etc.
� Examples include Mt. Fuji, Mt. Rainier, Mt. Vesuvius.
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Eruptive Style
� Will it flow, or will it blow? Two dominant styles.
� Effusive eruptions – Produce lava flows.
� Explosive eruptions – Blow up.
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Eruptive Style
� Effusive eruptions – Produce lava flows.
� Lava flows stream away from vents.
� Lava lakes can form around the vent.
� Can produce huge lava fountains.
� Commonly basaltic, these create shield volcanoes.
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Eruptive Style
� Explosive eruptions – Produce pyroclastic flows.
� Caused by gas pressure in the more viscous magma.
� Pressure is released explosively.
� Create stratovolcanoes.
� May create calderas.
� Blanket the landscape with tephra.
� Andesitic and rhyolitic compositions.
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Controls on Eruptive Style
� Viscosity – Controls the ease of lava flow.
� Basalt – Low viscosity lava flows away from vent.
� Felsic – High viscosity lava builds up at the vent.
� Gas Pressure – Greater P favors explosive style.
� Basalt – Low viscosity allows gas release.
� Felsic – High viscosity prevents gas release.
� Environment – Where eruption occurs is important.
� Subaerial lava flowing on land cools slower than…
� Submarine lava which is quickly quenched.
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Tectonic Settings
� Plate motion is a dominant control on volcanism.
� Volcanic types are linked to tectonic boundaries.
� mid-ocean ridges – Spreading axes.
� Convergent boundaries – Subduction zones.
� Continental rifts – Incipient ocean basins.
� Oceanic and continental hot spots – Mantle plumes.
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Mid-Ocean Ridge Eruptions
� Most lava erupts along the mid-ocean ridge (MOR).
� MOR-generated oceanic crust covers 70% of Earth.
� Basalt erupted from fissures quenches as pillows.
� Pillow mounds are pulled apart with plate motion.
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Convergent Boundaries
� Most volcanoes form at convergent boundaries.
� Volatiles from subducting plate initiate melting.
� Arc volcanoes develop on the overriding plate.
�May cut through either oceanic or continental crust.
� The “Ring of Fire” dominates Pacific margins.
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Continental Rifts
� Yield an array of volcano types reflecting…
� Partial melting of the mantle (mafic magmas).
� Partial melting of the crust (felsic magmas).
� Examples:
� East African Rift.
� Basin and Range Province.
� Mid-continent Rift.
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Oceanic Hot Spot Volcanoes
� Plume under an oceanic plate.
� Basalt erupts at the seafloor and forms a growing mound.
� A volcano builds above sea level to form an island.
� Then, basalt will not quench and can flow long distances.
� Lava builds upward and outward and the island grows.
� Submarine slumps remove large masses of the volcano.
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Continental Hot-Spot Volcanoes
� Continental Hot Spot – Cuts a continental plate.
� Yellowstone – Eruption ~ 640 Ka created a 100 km caldera.
�1,000 times more powerful than Mt. St. Helens.
�Deposited vast ignimbrite deposits.
�Magma beneath the caldera continues to fuel geysers
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Flood-Basalt Eruptions
� Voluminous lava eruptions above a plume.
� Thinned lithosphere erupts magma from long fissures.
� Lava spreads over large areas; great thicknesses stack up.
� Create plateaus called Large Igneous Provinces (LIPs).
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Iceland
� Iceland is a hot spot beneath a mid-ocean ridge.
� Lava has built the hot spot/ridge above sea level.
� The island is being torn apart by plate motion.
� Volcanoes trace the mid-ocean ridge rift valley.
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Predicting Eruptions
� Warning signs precede most eruptions.
� Earthquake activity – Magma flow increases seismicity.
� Heat flow – Magma causes volcanoes to “heat up.”
� Changes in shape – Magma causes volcanoes to inflate.
� Emission increases – Changes in gas mix and volume.
� These signs indicate that an eruption is imminent.
� They cannot predict eruption timing or style.
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Volcanoes and Climate
� Volcanic eruptions can be large enough to alter climate.
� Ash and aerosols high in the atmosphere block sunlight.
� This causes atmospheric cooling.
�1815 was the “year without a summer” due to Tambora.
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© 2012 Pearson Education, Inc.
End of Chapter 8
Chapter 11
Coastal Processes
Dr. Joao Santos
Chapter 11
Coastal Processes
Dr. Joao Santos
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Oceanography
� The oceans are responsible for our presence.
� Blue ocean covers 70.8% of the planet. Oceans…
� Serve as the basis for life on Earth.
� Regulate climate.
� Cycle mass and energy.
�Atmosphere.
�Hydrosphere.
�Lithosphere.
�Biosphere.
� 60% of humans live near
coasts.
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Undersea Landscapes
� Oceans exist because of differences in lithosphere.
� Continental lithosphere “floats higher” on the mantle.
� Oceanic lithosphere “floats deeper” in the mantle.
� Ocean basins collect water because they are lower.
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Undersea Landscapes
� The world’s ocean dominates the globe.
� Tectonic processes constantly configure oceans.
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Undersea Landscapes
� On the present configuration of tectonic plates…
� Most continental crust is in the northern hemisphere.
� Most oceanic crust is in the southern hemisphere.
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Undersea Landscapes
� The seafloor exhibits highly varied bathymetry.
� Continental shelf – Shallow (0 to 500 m), gently sloping
(0.3o).
� Continental slope – Descends from 500 m to 4 km at ~ 2o.
� Continental rise – Transition zone from 4 to 4.5 km.
� Abyssal plain – Flat, low-relief bottom below 4.5 km.
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Undersea Landscapes
� Submarine canyons crosscut continental shelves.
� Associated with large rivers.
� Erosion carved canyons during sea-level lowstands.
� Submerged canyons funnel sediments to deeper water.
� Submarine fans grow where canyons empty onto the rise.
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Undersea Landscapes
� Continental margins are called passive or active.
� A passive continental margin…
� Is located far from a tectonic plate boundary.
� Develops a broad shelf of sediment overlying sialic crust.
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Undersea Landscapes
� Continental margins are called passive or active.
� An active continental margin…
� Is immediately adjacent to a tectonic plate boundary.
� Characterized by a thin, narrow continental shelf.
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Ocean Water Composition
� Normal marine salinity, reflecting dissolved ions, is…
� 3.5% (35 grams per liter; 35,000 parts per million)
� Dissolved ions derive from chemical weathering of rocks.
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Ocean Water Composition
� Salt remains behind during freezing or evaporation.
� Desiccation yields evaporite mineral salts.
� Halite (NaCl).
� Gypsum (CaSO4
. 2H2O).
� Sylvite (KCl).
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Ocean Water Composition
� Surface salinity can vary above and below 3.5%.
� Higher salinity from evaporation and formation of sea ice.
� Lower salinity from rainfall, glacial melt, and river input.
� Salinity becomes more uniform with depth.
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� Currents ceaselessly move ocean water in 3-D.
� Surface currents (upper 100 m) due to wind shear.
� Currents spiral by Coriolis deflection into large gyres.
Oceanic Currents
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Downwelling Upwelling
Vertical Oceanic Currents
� Currents also transport ocean water vertically.
� Downwelling – Surface waters are drawn downward.
� Upwelling – Deep waters are pushed upward.
� Wind perpendicular to shore drives vertical flow.
� Onshore – Water piling up along coast drives downwelling.
� Offshore – Upwelling replaces water moved away.
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Vertical Oceanic Currents
� Thermohaline contrast also drives vertical currents.
� Temperature – Colder water is denser and sinks.
� Salinity – More saline water is denser and sinks.
� Polar water is both colder and saltier.
� Deep-ocean waters are replenished from the poles.
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Oceanic Currents
� Sinking polar water is replaced by surface flow.
� This process carries warm water up from the tropics.
� These surface currents warm northern oceans.
� This system forms a global “conveyor belt.”
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Tides
� Sea level rises and falls twice daily.
� High tide – Maximum tidal flooding.
� Low tide – Maximum tidal withdrawal.
� Tidal reach – The range between high and low tides.
� The intertidal zone lies between tides.
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Tides
� Tides are caused by a tide-generating force, due to…
� The gravitational pull of the Moon and the Sun.
� Centrifugal forces from the rotation of the Earth, Moon, and
Sun.
� The orbiting moon creates the strongest tidal effects.
� The sublunar bulge follows the moon’s orbit.
� A smaller bulge occurs on the opposite side of Earth.
� The bulges make high tides; between bulges are low tides.
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Tides
� Lunar and solar tidal effects interact.
� Positive alignment yields enhanced “spring” tides.
� Negative alignment results in dampened “neap” tides.
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Tides
� The magnitude and timing of tides varies widely.
� This reflects a complex interplay of factors:
� Relative orientation of the Sun and Moon.
� The orbital properties of the moon.
� Basin geometry.
� Air pressure.
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Waves
� Oceanic waves develop via friction of wind on water.
� Gentle wind creates small waves.
� Gales make giant waves.
� Waves translate the uppermost part of the water.
� Wave height, length, and period depend on wind speed,
wind duration, and distance of travel (fetch).
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Waves
� Definitions:
� Crest – Top of a wave.
� Trough – Low between
crests.
� Wavelength – Distance
between wave crests.
� Depth of influence (wave
base) is ½ the wavelength.
� Above wave base, water
moves in a circular motion.
� Below wave base, water is
not affected by wind waves.
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Waves
� As waves approach shore, wave base hits bottom.
� Friction slows wave motion near the sea floor.
� Near the surface, waves continue moving fast.
� The wave oversteepens and crashes onto the beach.
� This zone features a diverse array of environments.
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Waves
� Waves that crash onto the beach are called breakers.
� Wave energy is dissipated by turbulence.
� This creates frothy white water in the surf zone.
� A surge of water (swash) rushes up the beach face.
� Gravity pulls the backwash down the slope of the beach.
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Wave Refraction
� On an irregular shoreline, water depth varies.
� As waves drag on bottom, they are forced to bend.
� This process, (wave refraction), has consequences.
� Wave attack is concentrated against headlands.
� Wave attack is dissipated in embayments.
� This process tends to straighten an irregular shore.
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Longshore Currents
� Sediment is transported along the shore.
� Oblique waves push sediment sideways up the beach.
� Gravity then pulls this sediment straight downslope.
� This zig-zag pattern moves
sediment in one direction.
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Rip Currents
� Rip currents develop when wave attack is straight on.
� Water piles up on the beach and must return seaward.
�A rip current develops perpendicular to the beach.
�Rip currents are often strong; people drown fighting them.
� Rip currents dissipate away from the surf zone.
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Rip Currents
� Swimmers can easily survive rip currents.
� If caught in a rip current, don’t panic.
� Don’t swim against the current; swim parallel to shore.
� Or, ride the current out; waves will carry you back.
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Coastal Landforms
� A variety of landforms are found along coastlines.
� Broad, sandy beaches.
� Lush, swampy wetlands.
� Drowned river valleys.
� Steep cliffs.
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Beaches
� Gently sloping shorelines made of sediment.
� They are dynamic settings subject to constant change.
� Common as vacation destinations.
� Most people have experienced beaches.
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Beaches
� Beaches are dominated by sand.
� Gravel beaches reflect energetic surf and a rock supply.
� Muds are absent.
� Turbulent surf suspends and removes finer sediments.
� Muds are transported to lower-energy environments.
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Beaches
� Beach sediment compositions reflect geology.
� Quartz common.
� Carbonates in tropics.
� Resistant minerals.
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Beaches
� Beaches develop distinctive cross-sectional profiles.
� Profiles change seasonally with energy regime.
� Summer – Broad, sandy beach.
� Winter – Narrow, gravel beach.
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Beaches
� Distinct zones exist along a beach profile.
� Foreshore or intertidal – Region between high and low tide.
� Beach face – Steep, concave zone formed by wave swash.
� Backshore – Upper part of the beach.
�Beyond the reach of normal high tides.
�Often exhibit berms (stepped terraces of storm sediment).
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Beaches
� Longshore currents move sediment along beaches.
� This process, beach drift, moves tons of sand daily.
� Beach drift builds sandbars and sand spits.
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� Barrier islands are elongate, linear sandbars.
� They form where sand is plentiful.
� They create a protected backwater area called a lagoon.
� Barrier islands are common places for development.
� They change constantly.
Barrier Islands
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� Form in intertidal zones lacking strong waves.
� Common behind barrier islands or in estuaries.
� Consist of thinly laminated sand and mud.
� Ancient tidal flat sediments are well studied.
Tidal Flats
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� Along rocky coasts, bedrock rises out of the sea.
� Wave action is often powerful along rocky coasts.
� Concentrated wave energy acts to erode rock.
� Rocky coasts develop unique landforms.
Rocky Coasts
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� Wave-cut notches – Waves erode an overhang.
� The cliff collapses and process resumes.
� Over time, cliff retreat is marked by a wave-cut bench.
�An erosional remnant of former cliffs.
�Often exposed at low tide.
Rocky Coasts
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� Rocky headlands are preferentially eroded.
� Refracted waves focus energy to the sides of a headland.
� Erosional attack from both sides creates a sea arch.
� Collapse of the sea arch leaves remnant sea stacks.
Rocky Coasts
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� Coastal wetlands cover large areas of shore regions.
� They develop in places protected from waves and currents.
� Wetlands fuel high biological productivities.
� Vegetative characteristics are governed by climate.
�Temperate – Vegetated by trees, grasses, or mosses.
�Tropical – Mangrove-dominated.
Organic Coasts
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� Coral reefs grow in tropical marine settings.
� They create large structures of cemented skeletons.
� Among the most biologically
productive ecosystems.
Reefs
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� Coral reefs modify sediment accumulation.
� Reefs alter wave and current energy.
� They protect leeward environments.
� Abundant debris is shed to adjacent environments.
� Size / geometry defines patch, fringing, or atoll reefs.
Reefs
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� Coral atolls are reefs formed on a subsiding volcano.
� Reef is established when volcano is active.
� After extinction, volcano erodes and subsides.
� Coral reef can easily keep pace with subsidence.
� Reef continues long after volcano is below sea level.
Reefs
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
� River valleys flooded by marine water are estuaries.
� Characterized by mixing of fresh and salt water.
� Modern estuaries reflect glaciation.
�Rivers cut canyons during low sea level.
�Sea-level rise flooded these canyons.
Estuaries
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
� Flooded U-shaped valleys carved by glaciers.
� Form spectacular bedrock bounded troughs.
� Notable examples found in…
�Norway.
�British Columbia.
�New Zealand.
Fjords
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Coastal Variability
� Plate tectonic setting governs the style of coastline.
� Passive margin – Broad, low-lying coastal plains typical.
� Active margin – Uplifted, rocky coasts dominate.
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Coastal Variability
� Eustatic sea-level changes affect coasts worldwide.
� Inflation / deflation of mid-ocean ridge volumes.
� Glaciation / deglaciation traps or releases water.
�During the last ice age, sea level
was lower exposing more land.
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Coastal Variability
� Emergent coasts experience relative sea-level fall.
� Uplift due to tectonic processes.
� Eustatic sea-level drop.
� Emergent coasts characterized by…
� River incision, cliffs, wave-cut notches, and platforms.
� Terraces representing former sea-level positions.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Coastal Variability
� Submergent coasts experience relative sea-level rise.
� Subsidence of a passive margin (i.e. deltaic sediments).
� Eustatic sea-level rise.
� Submergent coasts characterized by…
� Flooded river or glacial valleys create estuaries and fjords.
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Coastal Variability
� Shoreline character is linked to sediment supply.
� Balance between accumulation and erosion.
�Accretionary coasts – Net sediment accumulation.
�Erosional coasts – Sediment removed faster than supplied.
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Coastal Variability
� Climate is a strong influence on shoreline character.
� Harsh weather accentuates erosion.
� Calm weather favors sediment accumulation.
� Tropics – Carbonate sediment, mangroves, and reefs.
� Temperate – Salt marshes.
� Arctic – Barren, lichen-covered coast.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Coastal Problems
� Contemporary sea level
changes.
� Sea level is presently rising.
� Rates of sea level rise may
increase from ice-cap melting.
� People living in low-lying
coastlines may be in jeopardy.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Coastal Problems
� Beach destruction.
� Storms (especially hurricanes) radically alter shorelines.
� Human development in coastal settings often affected.
� Construction in coastal settings is increasingly regulated.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 18: Amazing Ice: Glaciers and Ice AgesChapter 18: Amazing Ice: Glaciers and Ice Ages
Coastal Problems
� Artificial barriers are built to reduce beach erosion.
� Groins, jetties, and breakwaters arrest sediment transport.
� Usually this produces unintended consequences.
�Sediment deposition is enhanced in one place.
�Sediment erosion is accelerated in another.
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© 2012 Pearson Education, Inc.
End of Chapter 11
Chapter 9
Rivers and Flooding
Dr. Joao Santos
Chapter 9
Rivers and Flooding
Dr. Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Stream Flow
� Streams – Ribbons of water that flow down channels.
� Runoff – Water in motion over the land surface.
� Stream runoff is crucial for humans.
� Drinking water.
� Transportation.
� Waste disposal.
� Recreation.
� Commerce.
� Irrigation.
� Energy.
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Stream Flow
� Stream runoff also causes many problems.
� Flooding destroys lives and property.
� Stream runoff also causes many problems.
� Flooding destroys lives and property.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Stream Flow
� Stream runoff is an important geologic agent.
� Flowing water…
�Erodes, transports, and deposits sediments.
�Sculpts landscapes.
�Transfers mass from continents to ocean basins.
� Earth: Only planet in the solar system with flowing water.
� Without flowing water, Earth might resemble Mars.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
The Hydrologic Cycle
� Stream runoff is a component of the hydrologic cycle.
� Hydrologic cycle processes.
� Evaporation.
� Transpiration.
� Precipitation.
� Infiltration.
� Runoff.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Forming Streams
� Streamflow begins as water is added to the surface.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Forming Streams
� Streamflow begins as moving sheetwash.
� Thin surface layer of water.
� Moves down the steepest slope.
� Erodes substrate.
� Sheetwash erosion
creates tiny rill channels.
� Rills coalesce, deepen,
and downcut into channels.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Forming Streams
� Intense scouring marks entry into the channel.
� Rapid erosion lengthens the channel upslope.
� This process is called headward erosion.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Forming Streams
� Over time, nearby channels merge.
� Smaller tributaries join a larger trunk stream.
� The array of linked channels is a drainage network.
� Drainage networks change over time.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Drainage Networks
� Drainage networks often form geometric patterns.
� These patterns reflect underlying geology.
� Common drainage patterns.
� Dendritic – Branching, “treelike” due to uniform material.
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Drainage Networks
� Common drainage patterns.
� Radial – From a point uplift (mesa, volcano, etc.)
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Drainage Networks
� Common drainage patterns.
� Rectangular – Controlled by jointed rocks.
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Drainage Networks
� Common drainage patterns.
� Trellis – Alternating resistant and weak rocks.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Drainage Networks
� Common drainage patterns.
� Parallel – Streams developed on a uniform slope.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Drainage Basins
� Land areas that drain into a specific trunk stream.
� Also known as catchments or watersheds.
� Divides are uplands that separate drainage basins.
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Drainage Divides
� Watersheds exist in a
variety of scales.
� Tiny tributaries.
� Continental rivers.
� Large watersheds…
� Feed large rivers.
� Section continents.
� Continental divides
separate flow to
different oceans.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Permanent vs. Ephemeral
� Permanent streams
� Water flows all year.
� At or below water table.
� Humid or temperate.
�Sufficient rainfall.
�Lower evaporation.
� Seasonal discharge
variation.
� Ephemeral Streams
� Do not flow all year.
� Above the water table.
� Dry climates.
�Low rainfall.
�High evaporation.
� Flow mostly during rare
flash floods.
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� The amount water flowing in a channel.
� Volume of water passing a point per unit time.
�Cubic feet per second (ft3/s or cfs).
�Cubic meters per second (m3/s).
� Given by cross-sectional area times flow velocity.
� Varies seasonally due to precipitation and runoff.
Discharge
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Discharge
� Velocity is not uniform in all areas of a channel.
� Friction slows water along channel edges. Friction is…
�Greater in wider, shallower streams.
�Lesser in narrower, deeper streams.
� In straight channels, highest velocity is in the center.
� Few natural channels are straight.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Discharge
� Velocity is not uniform in all areas of a channel.
� In curved channels, max. velocity traces the outside curve.
�The outside curve is preferentially scoured and deepened.
�The deepest part of the channel is called the thalweg.
�Flow around curved channels follows a spiral path.
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Discharge
� Velocity is not uniform in all areas of a channel.
� Stream flow is characteristically turbulent.
�Chaotic and erratic.
�Abundant mixing.
�Swirling eddies.
�High velocity.
� Turbulence caused by…
� Flow obstructions.
� Shear in water.
� Turbulent eddies scour
the channel bed.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Erosional Processes
� Erosional processes – Streamflow does work.
� The energy imparted to streamflow is derived from gravity.
� Streams do work by converting potential to kinetic energy.
� Erosion is maximized during floods.
� Large water volumes.
� High water velocities.
� Abundant sediment.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Erosional Processes
� Streams scour, break, abrade, and dissolve material.
� Scouring – Running water picks up sediment and moves it.
� Breaking and lifting – The force of moving water can…
�Break chunks of rock off of the channel.
�Lift rocks off of the channel bottom.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Erosional Processes
� Abrasion – Sediment grains in flow “sandblast” rocks.
�Bedrock exposed in channels is often polished smooth.
�Gravel swirled by turbulent eddies drills holes in bedrock.
�These bowl-shaped depressions are called potholes.
�Potholes are often intricately sculpted.
� Dissolution – Mineral matter dissolves in water.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Sediment Transport
� The material moved by streams is the sediment load.
� There are 3 types of load.
� Dissolved load – Ions from mineral weathering.
� Suspended load – Fine particles (silt and clay) in the flow.
� Bed load – Larger particles roll, slide and bounce along.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Sediment Transport
� Sediment transport changes with discharge.
� High discharge – Large cobbles and boulders may move.
� Low discharge – Large clasts are stranded.
� Competence – The maximum size transported.
� Capacity – The maximum load transported.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Sediment Deposition
� When velocity decreases so does competence.
� Sediment grains drop out; water sorts them by size.
�Gravel settles in channels.
�Sands are removed from the gravels; muds from both.
�Sands drop out in near channel environments.
�Silts and clays are suspended only to settle in slack water.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Sediment Deposition
� Fluvial sediments are called alluvium.
� Channels may be decorated with mid-channel bars.
� Sands build up the point bars inside meander bends.
� Muds are deposited away from the channel during floods.
� A stream builds a sediment delta upon entering a lake.
Point Bar
Meander
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Longitudinal Changes
� The character of a stream changes with flow distance.
� In profile, the gradient describes a concave-up curve.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Longitudinal Changes
� The character of a stream changes with flow distance.
� Near the headwater source of the stream…
�Gradient is steep.
�Discharge is low.
�Sediments are coarse.
�Channels are straight and rocky.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Longitudinal Changes
� The character of a stream changes with flow distance.
� Toward the mouth…
�Gradient flattens.
�Discharge increases.
�Grain-sizes are smaller.
�Channels describe broad meander belts.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Base Level
� The lowest point to which a stream can erode.
� Ultimate base level is defined by the position of sea level.
�Streams cannot erode below sea level.
� A lake serves as a local (or temporary) base level.
� Base level changes cause stream re-adjustments.
�Raising base level results in an increase in deposition.
�Lowering base level accelerates erosion.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Base Level
� The lowest point to which a stream can erode.
� A ledge of resistant rock may define the local base level.
� Erosive forces act to slowly remove the resistant layer.
�This acts to restore the longitudinal profile.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Fluvial Landforms: Valleys and Canyons
� Land far above base level is subject to downcutting.
� Rapid downcutting creates an eroded trough.
� Canyon – Steep trough sidewalls form cliffs.
� Valley – Gently sloping trough sidewalls define a V-shape.
� Determined by rate of erosion vs. strength of rocks.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Valleys and Canyons
� Stratigraphic variation often yields a stair step profile.
� Strong rocks yield vertical cliffs.
� Weak rocks produce sloped walls.
� Geologic processes stack strong and weak rocks.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Valleys and Canyons
� Active downcutting flushes sediment out of channels.
� Valleys store sediment when base level is raised.
� Renewed incision creates stream terraces.
� Terraces mark former floodplains.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Rapids
� Rapids are turbulent water with a rough surface.
� Rapids reflect geologic control.
� Flow over resistant bedrock steps.
� Flow over large clasts.
� Abrupt narrowing of a channel.
� Sudden increase in gradient.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Waterfalls
� Streams that cascade or free-fall.
� Waterfall energy scours a plunge pool at the base.
� Basal erosion initiates collapse of overlying rocks.
� Waterfalls are temporary base levels.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Waterfalls
� Niagara Falls – Lake Erie drops 55 m to Lake Ontario.
� Dolostone caprock is resistant; underlying shale erodes.
� Blocks of unsupported dolostone collapse and fall.
� Niagara Falls continuously erodes south toward Lake Erie.
� Erosion since deglaciation has formed Niagara Gorge.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Waterfalls
� Niagara Falls.
� Diversion of American Falls revealed huge blocks of rock.
� The rate of waterfall retreat is presently 0.5 m/yr.
� Lake Erie will drain when the Falls reach it.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Alluvial Fans
� Alluvial fans build at the base of a mountain front.
� Sediments rapidly dropped near the stream source.
� Coarsest material found near the stream source.
� Sediments are fine and thin away from canyon stream.
� Sediments create a conical, fan-shaped structure.
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Braided Streams
� Form where channels are choked by sediment.
� Flow is forced around sediment obstructions.
� Diverging – converging flow creates sand and gravel bars.
� Bars are unstable, rapidly forming, and being eroded away.
� Flow occupies multiple channels across a valley.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Meandering Streams
� Channels can form intricately looping curves…
� Along the lower portion of the profile with a low gradient.
� Where streams travel over a broad floodplain.
� When substrates are soft and easily eroded.
� Meanders increase the volume of water in the stream.
� Meanders evolve.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Meandering Streams
� Meanders change from variation in thalweg position.
� Maximum velocity swings back and forth across flow.
� Fast water erodes one stream bank.
� The opposite bank collects sediment.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Meandering Streams
� Erosion accentuates the cut bank.
� High-velocity flow scours the outside of the meander bend.
� Collapsed cut-bank material is transported away.
� Deposition builds the point bar.
� Sediment accumulates inside the meander bend.
� Continued addition expands the point bar laterally.
Cut-Bank
Point Bar
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Meandering Streams
� Meanders become more sinuous with time.
� The cut bank erodes; the point bar accretes.
� Meander curves become more pronounced.
� Meanders elongate.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Meandering Streams
� Meander sinuosity increases until the meander is cut off.
� Cut banks converge and a meander neck thins.
� During flooding, high-velocity flow saws through the neck.
� The meander cut-off forms an oxbow lake.
� The oxbow fills with sediment, leaving an arcuate scar.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Meandering Streams
� Occupy only a small part of the floodplain.
� Floodplains are typically bounded by eroded bluffs.
� During floods, the floodplain may be immersed.
� Natural levees form ridges parallel to the channel.
� Made of sand dropped as floodwaters jump from channel.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Deltas
� Deltas form when a stream enters standing water.
� Current slows and loses competence; sediments drop out.
� Stream divides into a fan of small distributaries.
� Shape due to the interplay of flow, waves, and tides.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Deltas
� Distinct lobes preserve past Mississippi Delta history.
� The river periodically switches course via avulsion.
� River breaks through a levee upstream.
� Establishes a shorter, steeper path to the Gulf of Mexico.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Deltas
� Abandoned delta lobes are sediment-starved.
� Sediments deposited before avulsion slowly subside.
� Compaction, dewatering, and decay of organic matter.
� Lack of sediment nourishment.
� Abandoned delta lobes are eventually submerged.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Deltas
� Subsidence is a problem for cities built on deltas.
� Lack of regular flooding leads to sediment starvation.
� Subsidence below sea level magnifies flood risks.
�New Orleans is an example.
�Other cities also face this threat.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Drainage Evolution
� Landscapes evolve over time.
� Streamflow is the cause of most
landscape changes.
� Example:
� Uplift sets a new base level.
� Stream cuts into former surface.
� Valleys widen; hills erode.
� Landscape eroded to base level.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Drainage Evolution
� Stream rejuvenation is initiated by base level drop.
� Meanders initially develop on a gentle gradient.
� Uplift raises the landscape or base level falls.
� The river chainsaws downward
creating incised meanders.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Drainage Evolution
� Stream Piracy.
� A stream captures another’s flow.
� One stream, with more vigorous
headward erosion (a steeper
gradient), intercepts a neighbor.
� The captured stream flows into the
new stream.
� Below the point of capture, the old
stream dries up.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Drainage Evolution
� Superposed streams.
� Incises deformed terrain, yet ignores underlying structure.
�Streams initially develop in younger, flat-lying strata.
�The stream then chainsaws into the older underlying rocks.
�Stream maintains the geometry developed at an earlier time.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 14: The Geology of Streams and FloodsChapter 14: The Geology of Streams and Floods
Drainage Evolution
� Antecedent streams.
� Tectonic uplift may raise ground
beneath established streams.
� If erosion keeps pace with uplift, the
stream will cut through the uplift.
� If the rate of uplift exceeds erosion, the
stream is diverted by the range.
Edited by Joao Santos
© 2012 Pearson Education, Inc.
End of Chapter 9
Chapter 3
Minerals and
Rocks
Dr. Joao Santos
Chapter 3
Minerals and Rocks
Dr. Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature:
Minerals
• Fundamental building blocks of Earth.
• Various uses for modern economic
developments.
• Important clues for figuring out the history of
Earth.
• Knowledge of minerals and rocks as the first
important step to better manage Earth’s
resources.
Importance of Rocks and Minerals
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
• All matter, including minerals and rocks, made of
atoms.
• Atom structure: Nucleus (proton and neutron)
and surrounding electrons.
• Atomic number: The unique number of protons
in an element’s nucleus.
• Atomic mass number: The sum of the member of
protons and neutrons.
Basic Chemistry Review
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Rock-Forming Mineral Groups
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Minerals
� Minerals are the “building blocks” of rocks—hence, Earth.
� More than 4,000 are known.
� Dozens of new minerals are discovered annually.
� Human interest in minerals spans millennia.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Minerals
� Developed societies depend on mineral resources.
� Metals – Iron, copper, lead, zinc, nickel, aluminum, etc.
� Non-metals – Gypsum, limestone, aggregate, clay.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Minerals
Figure 3.2b
Figure 3.1
Figure 3.2a
� Economically important – Drive world economies.
� Historically important – Dictated human history.
� Iron.
� Copper.
� Gold.
� Diamonds.
� Gems.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Rocks
� Rocks are earth materials made from minerals.
� Most rocks contain more than one kind of mineral.
� Example: Granite
�K-feldspar – Pink.
�Quartz – Gray.
�Hornblende – Black.
� Some are monomineralic.
� Limestone (Calcite)
� Rock salt (Halite)
� Glacial ice.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Mineral Physical Properties
PyritePyrite
� Characteristics determined by your five senses.
� Used to ID minerals.
� Properties depend upon…
� Chemical composition.
� Crystal structure.
� Some are diagnostic.
Example: Pyrite (FeS2)
Cubic crystals, high specific gravity, striated crystal faces, black
streak, metallic luster, dull brassy color, sulfur smell when crushed,
erroneously mistaken for gold (fool’s gold).
� Minerals have unique sets of physical properties.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Mineral Physical Properties
Needle-like crystal habit
� Common properties of
minerals are…
� Crystal form.
� Crystal habit.
� Luster.
� Color.
� Streak.
� Hardness.
� Cleavage.
� Fracture.
� Specific gravity.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Color
Quartz – Many colorsQuartz – Many colors Malachite – Always greenMalachite – Always green
� Color is diagnostic for some minerals.
� Olivine is olive green.
� Azurite is always blue.
� Some minerals may exhibit a broad color range.
� Quartz (Clear, white, yellow, pink, purple, gray, etc).
� Color varieties often reflect trace impurities.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Streak
Hematite – Red-brown streakHematite – Red-brown streak
� Mineral color crushed on an unglazed porcelain plate.
� Streak is often a useful diagnostic property.
� Congruent streak – Streak color the same as the mineral.
�Magnetite – Black mineral; black streak.
� Incongruent streak – Streak color differs from the mineral.
�Chromite – Black mineral; greenish-brown streak.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Luster
Satin spar Gypsum – Satiny lusterSatin spar Gypsum – Satiny luster
Quartz – Vitreous lusterQuartz – Vitreous luster
� The way a mineral surface scatters light.
� Two subdivisions.
� Metallic – Looks like a metal.
� Nonmetallic.
�Vitreous (glassy).
�Satiny.
�Silky.
�Resinous.
�Pearly.
�Earthy (dull).
�Adamantine (brilliant).
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
� Scratching resistance of a mineral.
� Hardness compared to the Mohs hardness scale.
� Talc, Graphite.
� Gypsum.
� Calcite.
� Fluorite.
� Apatite.
� Orthoclase.
� Quartz.
� Topaz.
� Corundum.
� Diamond.
Hardness
Glass – Steel 5.5
Fingernail 2.5
Copper Penny 3.5
Steel File 6.5
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
PyritePyrite
Specific Gravity
Potassium FeldsparPotassium Feldspar
� Related to density (mass per volume)
� Mineral weight over weight of equal water volume.
� Specific gravity is “heft”– How heavy it feels.
� Pyrite – Heavy (SG 5.0)
� Feldspar – Light (SG 2.6)
� Pyrite “feels” heavier than feldspar.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Crystal Habit
Cubes Hexagonal PrismsBlades
RhombohedraDodecahedra
Octahedra
Tetragonal PrismsCompound Forms
� Crystal habit is the ideal shape of crystal faces.
� Ideal faces require ideal growth conditions.
� Many descriptive terms are used to characterize habit.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Crystal Form
Amethyst GeodeAmethyst Geode
� Minerals vary in crystal face development.
� Euhedral – Good crystal faces; grown in open cavity.
� Anhedral – No crystal faces; grown in tight space.
� Subhedral – Between the two.
� Face development indicates growth history.
� Anhedral crystals common; euhedral less so.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Cleavage
� Tendency to break along planes of lattice weakness.
� Cleavage produces flat, shiny surfaces.
� Described by the number of planes and their angles.
� Sometimes mistaken for crystal habit.
� Cleavage is through going; often forms parallel “steps”.
� Habit is only on external faces.
� 1, 2, 3, 4, and 6 cleavages possible.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Cleavage
Muscovite MicaMuscovite Mica
AmphiboleAmphibole
Potassium FeldsparPotassium Feldspar
� Examples of Cleavage:
� 1 direction
� 2 directions at ~ 90º
� 2 directions NOT at 90º
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Cleavage
CalciteCalcite
HaliteHalite
� Examples of Cleavage:
� Three directions at 90º
� Three directions NOT at 90º
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Fracture
ObsidianObsidian
� Some minerals lack planes of lattice weakness.
� Due to equal molecular bonds in all directions.
� These minerals don’t cleave; they exhibit fracture.
� Example: Quartz displays conchoidal fracture.
�Shaped like the inside of a clam shell.
�Breaks along smooth, curved surfaces.
�Produces extremely sharp edges.
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Mineral Compositions
74.3% of crustal minerals !!!
� Only about 50 minerals are abundant.
� 98% of crustal mineral mass is from eight elements.
� Oxygen O 46.6%
� Silicon Si 27.7%
� Aluminum Al 8.1%
� Iron Fe 5.0%
� Calcium Ca 3.6%
� Sodium Na 2.8%
� Potassium K 2.6%
� Magnesium Mg 2.1%
� All others 1.5%
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
Mineral Classes
Fluorite (Halide) Native CopperMalachite (Carbonate)
� Minerals are classified based upon the dominant anion.
� Silicates SiO2
4- Rock-forming minerals
� Oxides O2- Magnetite, Hematite
� Sulfides S- Pyrite, Galena
� Sulfates SO4
2- Gypsum
� Halides Cl- or F- Fluorite, Halite
� Carbonates CO3
2- Calcite, Dolomite
� Native elements Cu, Au, C Copper, Gold, Graphite
Edited by Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 3: Patterns in Nature: MineralsChapter 3: Patterns in Nature: Minerals
• Aggregated solids of minerals.
• Three major types of rocks classified by
origin, the way the rocks formed.
• Fundamental links between rocks and
environment (resources, sources for acid rain
drainage, land subsidence, structure
foundation failures, etc.).
• Rocks deform in response to geologic
forces/stress.
Rocks
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 4: Up from the Inferno: Igneous RocksChapter 4: Up from the Inferno: Igneous Rocks
Igneous Rocks
� Solidified molten rock.
� 1,100°°°°C to 650°°°°C.
� Temp depends on composition.
� Earth is mostly igneous rock.
� Magma – Subsurface melt.
� Lava – Melt at the surface.
� Volcanoes erupt magma.
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Igneous Rocks
� Melted rock can cool above or below ground.
� Intrusive igneous rocks – Cool slowly underground.
� Extrusive igneous rocks – Cool quickly at the surface.
�Lava – Cooled liquid.
�Pyroclastic debris – Cooled fragments.
�Volcanic ash.
�Fragmented lava.
� Many types of igneous rocks.
� All oceanic crust.
� Most continental crust.
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What is Magma Made of?
� Magmas have three components (solid, liquid and gas).
� Solid – Solidified mineral crystals are borne by the melt.
� Liquid – The melt itself is comprised of mobile ions.
�Dominantly Si and O; lesser Al, Fe, Mg, and K.
�Other ions present to a lesser extent.
� Different mixes of elements yield different magmas.
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What is Magma Made of?
� Gas – Magmas contain abundant dissolved volatile gas.
�Dry magma – Scarce volatiles.
�Wet magma – To 15% volatiles.
�Water vapor (H2O)
�Carbon dioxide (CO2)
�Sulfur dioxide (SO2)
�Nitrogen (N2)
�Hydrogen (H2)
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Magma Compositions
� There are four major magma types based on silica (SiO2)
percentage.
� Felsic (feldspar and silica) 66 to 76% SiO2.
� Intermediate 52 to 66% SiO2.
� Mafic (Mg and Fe-rich) 45 to 52% SiO2.
� Ultramafic 38 to 45% SiO2.
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Magma Compositions
� Composition controls magma density, T, and viscosity.
� The most important factor is silica (SiO2) content.
�Silica-rich magmas are thick and viscous.
�Silica-poor magmas are thin and “runny.”
� These characteristics govern eruptive style.
Type Density Temperature Viscosity
Felsic Very low Very low (600 to 850°°°°C) Very High: Explosive eruptions.
Intermediate Low Low High: Explosive eruptions.
Mafic High High Low: thin, hot runny eruptions.
Ultramafic Very high Very high (up to 1300°°°°C) Very low.
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Igneous Environments
� Two major categories – Based on cooling site.
� Extrusive settings – Cool at or near the surface.
�Cool rapidly.
�Chill too fast to grow big crystals.
� Intrusive settings – Cool at depth.
�Lose heat slowly.
�Crystals grow large.
� Most mafic magmas extrude.
� Most felsic magmas don’t.
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Interlocking or crystalline texture
Igneous Textures
� The size, shape, and arrangement of the minerals.
� Interlocking – Mineral crystals fit like jigsaw puzzle pieces.
� Fragmental – Pieces of preexisting rocks, often shattered.
� Glassy – Made of solid glass or glass shards.
Glassy texture
Fragmental texture
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Crystalline Igneous Textures
� Texture reveals cooling history.
� Aphanitic (finely crystalline).
�Rapid cooling.
�Crystals do not have time to grow.
�Extrusive.
� Phaneritic – (coarsely crystalline).
�Slow cooling.
�Crystals have a long time to grow.
�Intrusive.
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Igneous Classification
� Classification is based upon composition and texture.
� Composition – Felsic, intermediate, mafic, and ultramafic.
� Texture – Fine (aphanitic); coarse (phaneritic).
Type Aphanitic (fine) Phaneritic (coarse)
Felsic Rhyolite Granite
Intermediate Andesite Diorite
Mafic Basalt Gabbro
Ultramafic Very high Very high (up to 1300°°°°C)
A B
A B
C2 C1
C2C1
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� Form by very rapid cooling of lava in water or air.
� Glassy textures are more common in felsic magmas.
� They often preserve gas bubbles (vesicles).
� Underwater, basalt lava quenches into “pillows.”
Glassy Textures
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 4: Up from the Inferno: Igneous RocksChapter 4: Up from the Inferno: Igneous Rocks
Glassy Classification
� Glassy Igneous Rocks.
� Obsidian – Volcanic glass from rapidly cooled lava.
�Quenching – Lava flowing into water.
�High silica lavas – These can make glass without quenching.
� Pumice – Frothy felsic rock full of vesicles; it floats.
� Scoria – Glassy, vesicular, mafic rock.
Pumice Scoria
Obsidian
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Fragmental Textures
� Preexisting rocks that were shattered by eruption.
� After fragmentation, the pieces fall and are cemented.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 4: Up from the Inferno: Igneous RocksChapter 4: Up from the Inferno: Igneous Rocks
Fragmental Classification
� aka Pyroclastic – Fragments of violent eruptions.
� Tuff – Volcanic ash that has fallen on land and solidified.
� Volcanic breccia – Made of larger volcanic fragments.
Tuff
Breccia
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Sedimentary Rocks
� Sediments are the building blocks of sedimentary rocks.
� Sediments are diverse, as are the rocks made from them.
� Four classes:
� Clastic – Made from weathered rock fragments (clasts).
� Biochemical – Cemented shells of organisms.
� Organic – The carbon-rich remains of plants.
� Chemical – Minerals that crystallize directly from water.
ChemicalClastic OrganicBiochemical
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Clastic Sedimentary Rocks
� Clastic sedimentary rocks reflect several processes.
� Weathering – Generation of detritus via rock disintegration.
� Erosion – Removal of sediment grains from rock.
� Transportation – Dispersal by wind, water, and ice.
� Deposition – Settling out of the transporting fluid.
� Lithification – Transformation into solid rock.
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� Lithification – Transforms loose sediment into solid rock.
� Burial – More sediment is added onto previous layers.
� Compaction – Overburden weight reduces pore space.
�Sand – 10 to 20%
�Clay – 50 to 80%
� Cementation – Minerals grow in pores, “gluing” sediments.
Clastic Sedimentary Rocks
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Clastic Sedimentary Rocks
� Clast (grain) size – The average diameter of clasts.
� Range from very coarse to very fine.
� Boulder, cobble, pebble, sand, silt, and clay.
� With increasing transport, average grain size decreases.
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Clastic Sedimentary Rocks
� Clast composition – The mineral makeup of sediments.
� May be individual minerals or rock fragments.
� Mineral identities provide clues about…
�The source of the sediment.
�The environment of deposition.
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Clastic Sedimentary Rocks
� Angularity and sphericity – Indicate degree of transport.
� Fresh detritus is usually angular and non-spherical.
� Grain roundness and sphericity increases with transport.
� Well-rounded – Long transport distances.
� Angular – Negligible transport.
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Clastic Sedimentary Rocks
� Sorting – The uniformity of grain size.
� Well-sorted – Uniform grain sizes.
� Poorly sorted – Wide variety of grain sizes.
� Sorting becomes better with distance from source.
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Clastic Sedimentary Rocks
� Coarse clastics – Composed of gravel-sized clasts.
� Breccia – Comprised of angular fragments.
�Angularity indicates a lack of transport processing.
�Deposited relatively close to source.
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Clastic Sedimentary Rocks
� Coarse clastics – Composed of gravel-sized clasts.
� Conglomerate – Comprised of rounded gravel.
�Indicates water transport.
�Clasts bang together forcefully in flowing water.
�Collisons round angular corners and edges of clasts.
�Conglomerates are deposited at a distance from the source.
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Clastic Sedimentary Rocks
� Sandstone – Clastic rock made of sand-sized particles.
� Forms in many depositional settings.
� Quartz is, by far, the dominant mineral in sandstones.
� Sandstone varieties.
� Arkose – Contains abundant feldspar.
� Quartz sandstone – Almost pure quartz.
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Clastic Sedimentary Rocks
� Fine clastics – Composed of silt and clay.
� Silt-sized sediments are lithified to form siltstone.
� Clay-sized particles form shale.
� Fine clastics are deposited in quieter waters.
� Floodplains, lagoons, mudflats, deltas, deep-water basins.
� Organic-rich shales are the source of petroleum.
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� These are sediments derived from living organisms.
� Biochemical – Hard mineral skeletons.
� Organic – Cells of plants, algae, bacteria and plankton.
Biochemical and
Organic Rocks
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Biochemical Rocks
� Biochemical limestone – CaCO3 skeletal (shell) remains.
� Warm, tropical, shallow, clear, O2-rich, marine water.
� Diverse organisms (plankton, corals, clams, snails, etc.).
� Many textural varieties.
�Reefs.
�Shell debris.
�Lime mud (micrite).
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� Chert – Rock made of cryptocrystalline quartz.
� Formed from opalline silica (SiO2) skeletons.
�Diatoms.
�Radiolarians.
� Opalline silica added to bottom sediments dissolves.
� Silica pore fluids solidify to form chert nodules or beds.
Biochemical Rocks
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� Made from organic carbon.
� Coal – Altered remains of fossil vegetation.
�Accumulates in lush tropical wetland settings.
�Requires deposition in the absence of oxygen.
� Oil shale – Shale with heat altered organic matter.
Organic Rocks
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 6: Pages of Earth’s Past: Sedimentary RocksChapter 6: Pages of Earth’s Past: Sedimentary Rocks
Chemical Sedimentary Rocks
� Comprised of minerals precipitated from water solution.
� Evaporites – Created from evaporated seawater.
� Evaporation triggers deposition of chemical precipitates.
� Examples include halite (rock salt) and gypsum.
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Chemical Sedimentary Rocks
� Travertine – Calcium carbonate (CaCO3) precipitated
from groundwater where it reaches the surface.
� Dissolved calcium (Ca2+) reacts with bicarbonate (HCO3
-).
� CO2 expelled into the air causes CaCO3 to precipitate.
�Thermal (hot) springs.
�Caves.
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Chemical Sedimentary Rocks
� Dolostone – Limestone altered by Mg-rich fluids.
� CaCO3 altered to dolomite CaMg(CO3)2 by Mg
2+-rich water.
� Dolostone looks like limestone, except…
�It has a sugary texture and a pervasive porosity.
�It weathers to a buff, tan color.
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Metamorphic Rocks
� Metamorphic – Changed from an original “parent.”
� Meta = Change.
� Morph = Form or shape.
� Parent rocks are called
“protoliths.”
� Metamorphism can
occur to any protolith.
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Metamorphic Rocks
� Protoliths undergo pronounced changes in…
� Texture.
� Mineralogy.
� Due to changes in…
� Temperature.
� Pressure.
� Tectonic stress.
� Reaction with heated water.
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Metamorphic Character
� Metamorphic rocks have distinctive properties.
� Unique texture – Intergrown and interlocking grains.
� Unique minerals – Some that are only metamorphic.
� Unique foliation – A planar fabric from aligned minerals.
� These transformations can change the rock completely.
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Metamorphic Processes
� Metamorphic change occurs slowly in the solid state.
� Several processes are at work.
� Recrystallization – Minerals change size and shape.
� Phase change – New minerals form with…
�Same chemical formula.
�Different crystal structure.
�Example: Kyanite.
KyaniteKyanite
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Metamorphic Processes
� Neocrystallization – New minerals with changes in
temperature and pressure.
� Initial minerals become unstable and change to new
minerals.
�Original protolith minerals are digested in reactions.
�Elements restructure to form new minerals.
� In this way, a shale can transform into a garnet mica
schist.
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Metamorphic Processes
� Pressure solution – Mineral grains partially dissolve.
� Dissolution requires small amounts of water.
� Minerals dissolve where their surfaces press together.
� Ions from the dissolution migrate in the water film.
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Metamorphic Processes
� Plastic deformation – Mineral grains soften and deform.
� Requires elevated temperatures.
� Rock is squeezed or sheared.
� Minerals act like plastic, changing shape without breaking.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Causes of Metamorphism
� The agents of metamorphism are…
� Heat (T).
� Pressure (P).
� Compression and/or shear.
� Hot water.
� Not all agents are required; they often do co-occur.
� Rocks may be overprinted by multiple events.
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Heat (Temperature, T)
� Metamorphism occurs as the result of heat.
� Temperature (T) ranges between 200oC and 850oC.
� The upper T limit is…melting. It varies based upon rock
mineral composition and water content.
� Heat energy breaks and reforms atomic bonds.
� Sources of heat.
� Magmatic intrusions.
� Compression.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Pressure (P)
� P increases with depth in the crust.
� 270 to 300 bars per km (1 bar is almost 1 atm = 14.7 psi).
� Metamorphism occurs mostly in 2 to 12 kbar range.
� T and P both change with depth.
� Mineral stability is highly dependent upon T and P.
� This stability can be graphed on a “phase diagram.”
� Changes in T and P lead
to changes in minerals.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
� Pressure that is greater in one orientation.
� A commonplace result of tectonic forces.
� Two kinds of differential stress: Normal and shear.
� Normal Stress – Operates perpendicular to a surface.
�Tension – Pull-apart normal stress.
�Compression – Push-together normal stress.
Differential Stress
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Differential Stress
� Two kinds of differential stress: Normal and shear.
� Shear Stress – Operates sideways across a surface.
�Causes material to be “smeared out.”
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
� At higher T and P, differential stress deforms rock.
� Rocks change shape slowly without breaking.
Differential Stress
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Hydrothermal Fluids
� Hot water with dissolved ions and volatiles.
� Hydrothermal fluids facilitate metamorphism.
� Accelerate chemical reactions.
� Alter rocks by adding or subtracting elements.
� Hydrothermal alteration is called metasomatism.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rock Types
� Two major subdivisions of metamorphic rocks.
� Foliated – Has a through-going planar fabric.
�Subjected to differential stress.
�Classified by composition, grain size, and foliation type.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rock Types
� Two major subdivisions of metamorphic rocks.
� Nonfoliated – No planar fabric evident.
�Crystallized without differential stress.
�Classified by mineral composition.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rocks
� Slate – Fine clay, low-grade metamorphic shale.
� Has a distinct foliation called slaty cleavage.
�Develops by parallel alignment of platy clay minerals.
�Slaty cleavage oriented perpendicular to compression.
�Slate breaks along this foliation creating flat sheets.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rocks
� Phyllite – Fine mica-rich rock.
� Formed by low- to medium-grade alteration of slate.
� Clay minerals neocrystallize into tiny micas.
� Micas reflect a satiny luster.
� Phyllite is between slate and schist.
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� Schist – Fine or coarse rock with larger micas.
� Medium- to high-grade metamorphism.
� Has a distinct foliation called schistosity.
�Parallel alignment of large mica crystals.
�Micas are visible because they have grown at higher T.
� Schist often has other minerals due to neocrystallization.
�Quartz.
�Feldspars.
�Kyanite.
�Garnet.
�Staurolite.
�Sillimanite.
� Large non-mica minerals are called porphyroblasts.
Metamorphic Rocks
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rocks
� Gneiss – Has a distinct banded foliation.
� Light bands of felsic minerals (quartz and feldspars).
� Dark bands of mafic minerals (biotite or amphibole).
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rocks
� Compositional banding develops in several ways.
� Original layering in the protolith.
� Extensive high-temperature shearing.
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Migmatite
� Migmatite is a partially melted gneiss.
� It has features of igneous and metamorphic rocks.
� Mineralogy controls behavior.
� Light-colored (felsic) minerals melt at lower T.
� Dark-colored (mafic) minerals melt a higher T.
� Felsics melt first; mafics remain metamorphic.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rocks
� Nonfoliated rocks lack a planar fabric.
� Absence of foliation possible for several reasons:
�Rock not subjected to differential stress.
�Dominance of equant minerals.
�Absence of platy minerals like clays or micas.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rocks
� Amphibolite – Dominated by amphibole minerals.
� Basalt or gabbro protolith.
� Usually not well foliated.
� Hornfels – Alteration by heating.
� Associated with plutonic intrusions.
� Finely crystalline.
Amphibolite Hornfels
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Metamorphic Rocks
� Quartzite – Almost pure quartz in composition.
� Forms by alteration of quartz sandstone.
� Sand grains in the protolith recrystallize and fuse.
� Like quartz, it is hard, glassy, and resistant.
Metamorphic Alteration
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 7: Metamorphism: A Process of ChangeChapter 7: Metamorphism: A Process of Change
Metamorphic Rocks
� Marble – Coarsely crystalline calcite or dolomite.
� Forms from a limestone or dolostone protolith.
� Extensive recrystallization completely changes the rock.
� Original textures and fossils in the parent are obliterated.
� Used as a decorative and monument stone.
� Exhibits a variety of colors.
Metamorphic Alteration
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Rock Cycle
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© 2012 Pearson Education, Inc.
End of Chapter 3
Chapter 2
Internal Structure of Earth and Plate
Tectonics
Dr. Joao Santos
Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
A Layered Earth
� We live on the thin outer skin of Earth.
� Early perceptions about Earth’s interior were wrong.
� Open caverns filled with magma, water, and air.
� Furnaces and flames.
� We now know that Earth
is comprised of layers.
� The Crust.
� The Mantle.
� The Core.
�Outer Core.
�Inner Core.
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Earth’s Interior Layers
© W. W. Norton
� Crust
� Continental
� Oceanic
� Mantle
� Upper
� Lower
� Core
� Outer – Liquid
� Inner – Solid
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Two Types of Crust
� Continental crust – Granitic, underlies the continents.
� Average rock density about 2.7 g/cm3.
� Average thickness 35–40 km.
� Oceanic crust – Basaltic, underlies the ocean basins.
� Density about 3.0 g/cm3.
� Avgerage thickness 7–10 km.
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Earth’s Mantle
� Solid rock layer between the crust and the core.
� 2,885 km thick, the mantle is 82% of Earth’s volume.
� Mantle composition is the ultramafic rock peridotite.
� Below ~100–150 km, the rock is hot enough to flow.
� It convects: Hot mantle rises, cold mantle sinks.
� Three subdivisions: Upper, transitional, and lower.
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The Core
� Outer core
�Liquid iron-nickel-sulfur
�2255 km thick.
�Density – 10-12 g/cm3
� Inner core
�Solid iron-nickel alloy.
�Radius of 1220 km.
�Density – 13 g/cm3.
� An iron-rich sphere with a radius of 3,471 km.
� 2 components with differing seismic wave behavior.
� Flow in the outer core
generates the magnetic field.
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Lithosphere–Asthenosphere
� Lithosphere – The outermost 100–150 km of Earth.
� Nonflowing, rigid material that moves as tectonic plates.
� Made of 2 components: Crust and upper mantle.
� Asthenosphere – Upper mantle below lithosphere.
� Shallow under oceans; deep under continents.
� Flows as a soft solid.
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� The hypothesis that continents are mobile.
� Proposed by German meteorologist Alfred Wegener.
� The Origins of Oceans and Continents published in 1915.
� Wegener hypothesized a former supercontinent, Pangaea.
� Idea was founded on strong evidence.
�“Fit” of continents.
�Location of glaciations.
�Fossil organisms.
�Rock type and structural similarities.
�Paleoclimates preserved in rocks.
Continental Drift
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Continental Drift
� Wegener’s idea was debated and ridiculed.
� Most scientists didn’t believe him.
� Lack of a mechanism for drift a major criticism.
� Wegener died in 1930 at the age of 40.
� Lacking an advocate, the drift
hypothesis faded.
� His idea was revived in the 1950s.
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Continental Drift
� Wegener was right!
� Sea-floor spreading.
� Subduction.
� Plate Tectonics.
� Why did scientists dismiss Wegener’s model?
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Continental “Fit”
� Wegener noted that continents seem to fit together.
� He argued that the fit could not be coincidental.
� Present shorelines make a rough fit.
� The continental shelf edges make a better fit.
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Glacial Evidence
� Permian glacial till is found on four continents.
� The tills in Africa and India are now near the equator.
� A cooler earth? No. Permian tropical plants are known.
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Paleoclimatic Evidence
� Placing Pangaea over the Permian South Pole…
� He correctly predicted…
� Tropical coals.
� Tropical reefs.
� Subtropical deserts.
� Subtropical evaporites.
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Fossil Evidence
� Identical fossils found on widely separated landmasses.
� Mesosaurus – A freshwater reptile.
� Glossopteris – A subpolar plant with heavy seeds.
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Fossil Evidence
� Identical fossils found on widely separated land.
� Lystrosaurus – A non-swimming, land-dwelling reptile.
� Cynognathus – A non-swimming, land-dwelling mammal-
like reptile.
� These organisms could not
have crossed an ocean.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
� Geologic phenomenan match across the Atlantic.
� Geologic structures.
� Rock types.
� Rock ages.
Matching Geology
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� Geologic phenomenan match across the Atlantic.
� Mountain belts.
�The Appalachians.
�The Caledonides.
Matching Geology
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Criticisms of Drift
� Why wasn’t the continental drift hypothesis accepted?
� There were no mechanisms for moving continents.
� When Wegener died, the debate did too.
� The drift hypothesis needed new and different evidence.
� This was provided by paleomagnetism.
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The Earth’s Magnetic Field
� Earth’s magnetic field acts like a giant bar magnet.
� It’s N and S ends are tilted ~11° from the axis of rotation.
� Measured everywhere on Earth, it extends out into space.
� Some iron minerals in rocks align to the magnetic field.
� This permits some rocks to preserve magnetic information.
� Preserved magnetism can be read from these rocks.
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Magnetic Poles
� The “bar magnet” intersects Earth’s surface.
� Magnetic North Pole; magnetic south pole.
� Differs from geographic north pole (rotational axis).
� The magnetic poles move constantly, but stay in the
vicinity of the N and S geographic poles.
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� Above 350-550°C.
� Thermal energy of atoms high.
� Magnetic dipoles randomly oriented.
� No magnetic signature.
� Below 350-550°C.
� Thermal energy slows atoms.
� Dipoles align with Earth’s field.
� Material permanently magnetized.
� Fe-minerals can lock in the Earth’s
magnetic signal at the time formed.
� Can be used to determine lat / long.
Magnetic Overprinting
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Paleomagnetism
� Rock magnetism can be measured in the laboratory.
� Study of fossil magnetism is called paleomagnetism.
� Ancient rocks reveal latitudes / longitudes unlike today.
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Polar Wander
� Paleomagnetism from ancient lavas didn’t align with the
present magnetic field.
� This lack of alignment indicates past magnetic polar
wandering.
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Polar Wander
� Each continent had a separate polar-wander path.
� Either the location of the magnetic pole is not fixed, or…
� The lava flows themselves have moved.
� These curves align when continents are assembled.
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Apparent Polar Wander
� Polar wander is now known to be an artifact.
� Not the signature of a wandering pole on a fixed continent.
� The signature of a fixed pole on a wandering continent.
� Apparent polar wander is strong evidence for drift.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
� Sonar was used to map the ocean bathymetry.
� Oceanographers were surprised to discover that…
� The deepest parts of the ocean occur near land.
� A mountain range runs through every ocean basin.
� Submarine volcanoes form lines across ocean floors.
The Ocean Floor
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The Ocean Floor
� Modern views of the ocean floor reveal…
� Mid-ocean ridges.
� Trenches.
� Fracture zones.
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New Observations: Oceanic Crust
� By 1950, we had learned much about oceanic crust.
� Oceanic crust is covered by sediment. It is…
� Thickest near the continents.
� Thinnest (or absent) at the mid-ocean ridge.
� Oceanic crust is mafic (basalt and gabbro).
� No granitic rocks.
� No metamorphic rocks.
� High heat flow characterizes the mid-ocean ridge.
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New Observations: Oceanic Crust
� Belts of concentrated subsea earthquakes were found.
� The earthquakes were surprising. They were limited to…
� Parts of oceanic fracture zones.
� Mid-ocean ridge axes.
� Deep ocean trenches.
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Sea-Floor Spreading
� In 1960, Harry Hess published his “Essay in Geopoetry.”
� He called his theory “sea-floor spreading”.
� Upwelling mantle erupts at the mid-ocean ridges.
� New crust moves away from ridges, gathering sediment.
� At trenches, the sea-floor dives back into the mantle.
� Provided a potential mechanism for continental drift.
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Sea-Floor Spreading
� Drilling in the late 1960s recovered crust samples.
� Ages increase away from the mid-ocean ridge.
� Ages are “mirror images” across the mid-ocean ridge.
� Strong supporting evidence for
sea-floor spreading.
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Plate Tectonics
� The paradigm of “How the Earth Works.”
� Earth’s outer shell is broken into rigid plates that move.
� Moving plates change the face of planet Earth.
� A case study of a Scientific Revolution.
� A powerful idea based on multiple lines of evidence.
� Allows scientists to predict events and rebuild the past.
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Plate Tectonics
� Tectonic theory evolved in the 1960s.
� Previous research provided a strong foundation.
� Wegener (1915) – Evidence supporting continental drift
� Hess / Dietz (1960) – The sea-floor spreading hypothesis.
� By 1968, evidence for tectonics was overwhelming.
� This evidence changed the view of most geologists.
� Even reluctant scientists were eventually won over.
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Plate Tectonics
� Plate Tectonic theory is powerful.
� It provides a unified mechanism explaining:
� Igneous, sedimentary and metamorphic rocks.
� The distribution of earthquakes and volcanoes.
� The origin of continents and ocean basins.
� The distribution of fossil plants and animals.
� The genesis and destruction of mountain chains.
� Continental drift.
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Lithosphere
� Tectonic plates are fragments of lithosphere.
� Lithosphere is made of both crust and the upper mantle.
� The lithosphere is in motion over the asthenosphere.
� Lithosphere bends elastically when loaded.
� Asthenosphere flows plastically when loaded.
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Two Types of Lithosphere
� Continental ~ 150 km thick.
� Granitic crust.
�35-40 km thick.
�Lighter (less dense) .
�More buoyant – Floats higher.
� Oceanic ~ 7 to 100 km thick.
� Basaltic crust.
�7-10 km thick.
�Heavier (more dense).
�Less buoyant – Sinks lower.
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Plate Boundaries
� Lithosphere is fragmented into ~ 20 tectonic plates.
� Plates move continuously at a rate of 1 to 15 cm/yr.
� Slow on a human time scale; extremely rapid geologically.
� Plates interact along their boundaries.
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� Locations on Earth where tectonic plates meet.
� Identified by concentrations of earthquakes.
� Associated with many other dynamic phenomena.
� Plate interiors are almost earthquake free.
Plate Boundaries
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Continental Margins
� Where land meets the ocean.
� Margins near plate boundaries are “active.”
� Margins far from a plate boundaries are “passive.”
� Passive margin continental crust thins seaward.
� Transitions into oceanic crust.
� Traps eroded sediment.
� Develops into the
continental shelf.
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Plate Boundaries: Three Types
� Divergent – Tectonic plates move apart.
� Lithosphere thickens away from the ridge axis.
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Plate Boundaries: Three Types
� Convergent – Tectonic plates move together.
� The process of plate consumption is called subduction.
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Plate Boundaries: Three Types
� Transform – Tectonic plates slide sideways.
� Plate material is neither created, nor destroyed.
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Divergent Boundaries
� Sea-floor spreading causes plates to move apart.
� Magma wells up to fill the gap.
� Magma cools, adding material to each plate.
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Divergent Boundaries
� Sea-floor spreading progression.
� Early stage
�Rifting has progressed to Mid-Ocean Ridge formation.
�Before substantial widening of the ocean.
�Forms a long, thin ocean basin with young oceanic crust.
� Example: The Red Sea
Note: This diagram only depicts the crust, not the entire lithosphere.
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Divergent Boundaries
� Sea-floor spreading progression.
� Mid-stage
�Ocean begins to widen.
�New seafloor is added at the Mid-Ocean Ridge.
�Continents move farther apart.
� Example: Greenland and the North Atlantic.
Note: This diagram only depicts the crust, not the entire lithosphere.
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Divergent Boundaries
� Sea-floor spreading progression.
� Late Stage
�Mature, wide ocean basin.
�Linear increase in age with distance from central ridge.
�Edge of ocean basin – oldest; ridge proximal – youngest.
� Example: The Atlantic Ocean
Note: This diagram only depicts the crust, not the entire lithosphere.
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Mid-Ocean Ridges
� Linear mountain ranges in Earth’s ocean basins.
� Example: The Mid-Atlantic Ridge
� Snakes N-S through the entire Atlantic Ocean.
� Elevated ridge (1500 km wide) 2 km above abyssal plains.
� Axial rift valley.
�500 m deep.
�10 km wide.
�Symmetric.
�Site of eruptions.
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Mid-Ocean Ridges
� Sea-floor spreading opens the axial rift valley.
� Rising asthenosphere melts, forming mafic magma.
� Pooled magma solidifies into oceanic crustal rock.
� Pillow basalt – Magma quenched at the sea floor.
� Dikes – Preserved magma conduits.
� Gabbro – Deeper magma.
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Mid-Ocean Ridges
� “Black smokers” are found at some MORs.
� Water entering fractured rock is heated by magma.
� Hot water dissolves minerals and cycles back out of rock.
� When water reaches the sea, minerals precipitate quickly.
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Ocean Crustal Age
� Oceanic crust spreads away from the ridge axis.
� New crust is closer to the ridge; older crust farther away.
� Oldest oceanic crust is found at the far edge of the basin.
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� The hot asthenosphere is at the base of the MOR.
� Aging ocean crust moves away from this heat source…
� Cooling, increasing in density and slowly sinking.
� Accumulating an increasing thickness of sediment.
Oceanic Lithosphere
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Convergent Boundaries
� Lithospheric plates move toward one another.
� One plate dives back into the mantle (subduction).
� The subducting plate is always oceanic lithosphere.
� Subduction recycles oceanic lithosphere.
� Subduction is balanced by sea-floor spreading.
� Earth maintains a constant
circumference.
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Subduction
� Old oceanic lithosphere is more dense than mantle.
� A flat-lying oceanic plate doesn’t subduct easily.
� Once bent downward, however, the leading edge sinks
like an anchor rope.
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Convergent Boundaries
� The subducting plate descends at an average of 45°°°°
� Plate descent is revealed by Wadati-Benioff earthquakes.
�Mark frictional contact and mineral transformations.
�Earthquakes deepen away from trench.
� Quakes cease below 660 km.
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Fate of Subducted Plates?
� Plate descent may continue past the earthquake limit.
� The lower mantle may be a “plate graveyard.”
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Subduction Features
� Subduction is associated with unique features.
� Accretionary prisms.
� Volcanic arcs.
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� Accretionary Prism – A deformed sediment wedge.
� Sediments are scraped off of subducting plates.
� This thrusts them onto the overriding plate.
� Contorted prism sediments can be pushed above sea-level.
�Olympic Peninsula.
�Taiwan.
Convergent Boundaries
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Convergent Boundaries
� Volcanic Arc – A chain of volcanoes on overriding plate.
� The descending plate partially melts at ~ 150 km depth.
� Magmas burn through overriding plate.
� Volcanic arcs are curved because the Earth is a sphere.
� Arc type depends upon the overriding plate.
� Continental crust – Continental Arc.
� Oceanic – Island Arc.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Transform Boundaries
� Lithosphere slides past; not created or destroyed.
� Many transforms offset spreading ridge segments.
� Some transforms cut through continental crust.
� Characterized by…
� Earthquakes.
� Absence of volcanism.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Oceanic Transforms
� The Mid-Ocean Ridge axis is offset by transform faults.
� A geometric necessity for a line spreading on a sphere.
� Transforms bear strong evidence of sea-floor spreading.
�Abundant earthquakes common when offsets are opposed.
�Earthquakes vanish when offsets are concurrent.
Figure 2.23a
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Transform Boundaries
� Continental transforms – Chop continental crust.
� Example: The San Andreas Fault.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Triple Junctions
� Places where three plate boundaries coincide.
� Multiple boundary combinations occur.
� Triple junctions migrate and change across time.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
� Volcanic plumes independent of tectonic plates.
� Most are located far from plate boundaries.
� Comprised of mafic magmas from the lower mantle.
� Tattoo overriding plates with volcanoes.
Hot Spots
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Hot Spots
� Hot spot perforates overriding plate.
� Volcano builds above sea level.
� Plate motion pulls volcano off plume.
� Volcano goes extinct and erodes.
� Subsidence creates a guyot.
� Hot spots reinforce
sea-floor spreading.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Hot Spots
� Hot-spot seamounts age away from originating hot spot.
� Age change marks rate of plate motion.
� Line of seamounts indicates direction of plate motion.
Figure 2.25a
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Tectonic Boundaries Evolve
� Plate boundaries change over geologic time.
� Oceanic plates are…
� Created at mid-ocean ridge spreading centers.
� Destroyed at subduction zones.
� Continental plates are…
� Torn apart at rifts.
� Joined during collision.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
� Continental lithosphere can break apart.
� Lithosphere stretches and thins.
� Brittle upper-crust faults.
� Ductile lower-crust flows.
� Asthenosphere melts.
� Melt erupts.
� Continuation of this
process leads to full
sea-floor spreading.
Continental Rifting
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Continental Rifting
� Example: East Africa.
� The Arabian plate is rifting from the African plate.
� Rifting has progressed to sea-floor spreading in…
�The Red Sea
�The Gulf of Aden
� Rifting continues along the
East African Rift.
�Thinned crust.
�Elongate trough.
�Volcanoes.
� The rift and 2 spreading ridges
comprise a triple junction.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Plate Collision
� Subduction consumes ocean basins.
� Ocean closure ends in continental collision.
� Buoyant continental crust will not subduct.
� Subduction ceases and mountains are uplifted.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Plate Collision
� Plate tectonic collision may involve…
� Two continents.
� A continent and an island arc.
� Collision “sutures” the convergent plate boundary.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Driving Mechanisms
� What drives plate motion?
� Old idea: Plates are dragged atop a convecting mantle.
�Plate motions are much too complex.
�Convection does occur.
�It is not the prime driving mechanism.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Driving Mechanisms
� Modern thinking: Two other forces drive plate motions.
� Ridge-push – Elevated MOR pushes lithosphere away.
� Slab-pull – Gravity pulls a subducting plate downward.
� Convection in the asthenosphere adds or subtracts.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Plate Velocities
� Absolute plate velocities may be mapped by…
� Plotting plate motion relative to a fixed spot in the mantle.
� Measuring volcano ages / distance along a hot-spot track.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
Plate Velocities
� Plate vectors are determined GPS measurements.
� Global Positioning System (GPS) uses satellites.
� Knowledge of plate motion is now accurate and precise.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
The Dynamic Planet
� Plate Tectonics: The key to understanding geology.
� Mantle is transferred to the surface and back down again.
� The interior and surface of Earth are in constant motion.
� PTs explains earthquakes, volcanoes and continental drift.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
The Dynamic Planet
� Earth’s surface changes continuously.
� These changes appear slow to us.
� Geologically, change is rapid.
� Earth looked very different in the past.
� Earth will look very different in the future.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
The Dynamic Planet
� Plate Tectonics Summary: Ocean floor created at mid-ocean ridges
is consumed at oceanic trenches.
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Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 2: The Way the Earth Works: Plate TectonicsChapter 2: The Way the Earth Works: Plate Tectonics
The Dynamic Planet
� Plate Tectonics Summary: Ocean floor created at mid-ocean ridges
is consumed at oceanic trenches.
Edited by Joao Santos
© 2012 Pearson Education, Inc.
End of Chapter 2