Help with what needs to be answred
- Identify geographic features associated with plate boundaries (remembering)
- Describe how bathymetry in the ocean indicates plate movement and boundaries (understanding)
- Determining elevation and calculating slope (analyzing)
GEOL1403/Lab 1
Name: ———————————Your total=
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Date:
SEA FLOOR AND PLATE TECTONICS
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Sources of Heat for Earth Processes
o Some of the heat that affects geologic processes comes from the Sun and some comes from inside the
Earth. Each one of these heat sources play a role in Earth processes.
o In the upper 10 km of the crust, the geothermal gradient is typically about 25°C per km, but can range
from 15°C/km to 50°C/km. In the diagram below, plot these three geothermal gradients for the
upper 10 km of the Earth. …………………………………………………………………………………………….(5 pts)
o The deepest mine on Earth (TauTona in Carletonville, South Africa) penetrates to a depth of about
3895m. Using the geothermal gradients, you just drew, what range of temperatures would you expect
in the mine?
Temperatures range is:
•
Rates of Mountain and Ocean Formation
a. Rates of uplift and erosion. …………………………………………………………………………………………(5 pts)
o The following questions give you a sense of the rates at which uplift, and erosion take place. We will
assume that uplift and erosion do not occur at the same time – that the mountains are first uplifted
and only then does erosion begin – whereas the two processes actually operate simultaneously.
o
If mountains rose by 1 mm/yr., how high would they be (in meters) after
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GEOL1403/Lab 1
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1,000 years? _____________
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10,000,000 years? ______________
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50 million years? ________________
o
The Himalayas now reach an elevation of 8.8 km, and radiometric dating suggests that their uplift
began about 45 Ma ago. Assuming a constant rate of uplift, how fast did the Himalayas rise?
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km/yr? ____________________________________________
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m/yr? _____________________________________________
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mm/yr? ____________________________________________
o
Observations of modern mountain belts suggest that ranges erode at rates of 2 mm per 10 years. At
this rate, how long would it take to erode the Himalayas down to sea level?
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Years? __________________
b. Rates of seafloor spreading. ……………………………………………………………………………………(3 pts)
o Today the Atlantic Ocean is about 5,700 km wide at the latitude of Boston. At one time, however,
there was no Atlantic Ocean because the east coast of North America and the northwest coast of
Africa were joined in a huge supercontinent. The Atlantic Ocean started to form “only” 185,000,000
years ago, as modern North America split from Africa and the two slowly drifted apart in a process
called seafloor spreading.
o Assuming that the rate of seafloor spreading has been constant, at what rate has North America been
moving away from Africa?
•
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mm/yr? __________________________
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km/million years? ____________________
Recognizing Plates and Plate Boundaries …….…………………………………………..(5 pts)
o On the attached satellite image of the Atlantic Ocean, label/highlight the following features:
– mid oceanic ridge, active fault, active continental margin, passive continental margin,
abyssal plain, continental shelf, transform boundary, trench, and subduction boundary.
– What is the name of the plate on which USA resides?
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Does this plate consist of continental lithosphere? Oceanic lithosphere? Or both?
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Where does the lithosphere of the Atlantic Ocean form? ________________
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What kind of plate boundary occurs along the west coast of South America?
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GEOL1403/Lab 1
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GEOL1403/Lab 1
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Visit the Latest Earthquake Tracker in the following link, then fill out the table for the latest
great magnitude (> 6) ones. http://ds.iris.edu/seismon/bigmap/index.phtml
Location
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Latitude
Longitude
Magnitude
Name of plate
Plate boundary
Comparing Seafloor Spreading Rates at Different Ridges ………………………………………(5 pts)
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GEOL1403/Lab 1
Magnetic reversals are found worldwide,
so magnetic stripes should be the same
width in every ocean if the rate of sea-floor
spreading is the same at all ridges. If a
particular anomaly is wider in one ocean
than another, however, it must result
from faster spreading. The figure on the
right shows simplified magnetic stripes
from the South Atlantic and Pacific oceans,
the ages of the rocks, and the distance from
the spreading center (Ocean-ridge crest
line, red in your lab book). For simplicity,
only the most recent 80 million years of
data are shown for the two oceans, and we
will only estimate the spreading rate for
that time span.
o Measure the width of the South
Atlantic
Ocean
________________ km
o Estimate the average rate at which
the South Atlantic Ridge has been
opening over the 80 million years
for which data are provided
_________________ cm/yr.
o Now look at the data for the East
Pacific Rise and its spreading
center, will the spreading rate be
the same, greater, or less than
that of the South Atlantic?
o Now get the details. Measure the width of the South Pacific Ocean. _________________ km
o What is the spreading rate of the East Pacific Rise?
___________________ cm/yr
and______________________ km/million years
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GEOL1403/Lab 1
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Use of the GeoMapApp: …………………………………………………………………………………………..(10 pts)
o Web URL http://www.geomapapp.org to open the application GeoMapApp which you will be using
to answer many of the following questions. General directions are provided in the lab activity but
as the website and map often change, use logic and to navigate to find the information you need.
(There may be an icon on your computer desktop to start this program; if so, use it instead of the Web
site.)
o
Once on the website, use the Download links on the left. You will have to run the .exe after it
downloads. You may need to download an updated version of Java. Both Java and GeoMapApp are
free to download and run.
Once the GeoMapApp.exe is launched, a new window will open entitled GeoMapApp. Select
“Agree” and the program will open.
o
Task: Learning about Trenches
–
Use the smaller box in the upper right-hand corner insert of the map display to move to a different
location on the globe, southeast of Japan (or zoom way out, then in again).
The deepest point in the ocean, Challenger Deep, is located in the Marianas Trench. Marianas
Trench is located southeast of Japan.
Get a wide view of Southeast Asia and look in the ocean floor to find a large, nearly semicircular
gash—the trench.
Challenger Deep is near the south end of the trench, at about 142oE,
11oN. Zoom in on the Challenger Deep.
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What type of plate boundary is typically associated with trenches?
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Would you say that this area is or is not seismically active? Why or why not?
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Why does the color on the map darken as you approach the trench?
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What is the term used to describe a chain of volcanic islands located along a subduction zone?
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GEOL1403/Lab 1
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Using the color patterns, you saw on the Marianas Trench, find the trench between Antarctica
and South America. (Most of this trench is oriented N-S.)
Give its latitude and longitude. Zoom out or in as needed.
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Is the chain of volcanic islands located to the east or west of this oceanic trench?
Task: Learning about Continental Margins
– Center your view on South America. Zoom in/out until you can see both the east and
west coasts of South America and a little ocean on either side of the continent.
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Why is the area along the edges of the continent a grey color rather than the blue of the ocean?
What would this feature be called?
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Use the Distance/Profile Tool to measure the width of the grey area on the WEST coast (at
about 4oN, 78o15’W).
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What type of continental margin is present here?
Active
OR
Passive
What type of plate boundary might be found here (subduction, transform or spreading)?
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–
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On the EAST coast of South America (at about 3oN, 49oW), what is the width of the grey area?
What type of continental margin is present here?
Active
OR
Passive
What type of plate boundary would be found here?
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