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Introductory Geology
Pl ate Tectonics
4.11 STUDENT RESPONSES
The following is a summary of the questions in this lab for ease in submitting
answers online.
1. Brazil (Latitude and Longitude)
2. Angola (Latitude and Longitude)
3. Measure in centimeters the distance (Map Length) between the two points you
recorded in the previous question. Given that this portion of Pangaea broke
apart 200,000,000 years ago, calculate how fast South America and Africa are
separating in cm/year? (Hint: Speed= Distance/Time)
4. When will the next supercontinent form? Examine the Western Coast of South
America, the Eastern Coast of Asia, and the Pacific Ocean. If South America and
Africa are separating and the Atlantic Ocean is growing, then the opposite must
be occurring on the other side of the earth (the Americas are getting closer to
Asia and the Pacific Ocean is shrinking). How far apart are North America and
Mainland Asia in cm? (measure the distance across the Pacific at 40 degrees
north latitude- basically measure between Northern California and North
Korea)? Take that distance and divide it by the speed you calculated in question
3 to estimate when the next supercontinent will form. Show your work!
5. How far have the snake fossils moved apart since they were originally deposited?
a. 1250 miles
b. 1700 miles
c. 2150 miles
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d. 2700 miles
Introductory Geology
Pl ate Tectonics
6. Given that this portion of the Australian plate moves at a speed of 2.2 inches
per year, how old are the snake fossils?
a. 310 million years old
b. 217 million years old
c. 98 million years old
d. 62 million years old
e. 34 million years old
7. There are fossils such as Glossopteris and Lystrosaurus that are found in
rocks in South America and Africa that indicate they were part of Pangaea
approximately 200 million years ago. These same fossils can be found in
Australia, which indicates it, along with Antarctica, was also part of Pangaea at
that time. Based on your answer to question 6 which of the following statements
about the break-up of Pangaea is TRUE?
a. Australia and Antarctica separated before the break-up of Pangaea.
b. Australia and Antarctica separated during the break-up of Pangaea.
c. Australia and Antarctica separated after the break-up of Pangaea.
8. Consider the ages and positions of the islands listed above along with what
you know about plate tectonics and hotspots. In what general direction is the
Pacific Plate moving?
a. Northwest
b. Southeast
c. Northeast
d. Southwest
9. How fast was the Pacific plate moving during the last 1.1 million years between
the formation of the Big Island and Maui in cm/year? To calculate this divide the
distance (in centimeters) between the two islands by the difference in their ages.
10. How fast was the Pacific plate moving from 7.2 million years ago to 4.7 million
years ago between the formation of Kauai and Nihoa in cm/year? To calculate
this divide the distance (in centimeters) between the two islands by the
difference in their ages.
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Introductory Geology
Pl ate Tectonics
11. Examine the headings of the measurements that you took for the previous
two questions. The headings indicate the direction the Pacific Plate is moving
over the hot spot. How does the direction of motion of the Pacific Plate during
the last 1.1 million years differ from direction of movement between 4.7 and
7.2 million years ago? The direction of plate movement in the last 1.1 million
years________.
a. shows no change
b. has become more southerly
c. has become more northerly
12. Zoom out and examine the dozens of sunken volcanoes out past Nihoa, named the
Emperor Seamounts. As one of these volcanic islands on the Pacific Plate moves
off the hotspot it becomes inactive, or extinct, and the island begins to sink as it
and the surrounding tectonic plate cool down. The speed the islands are sinking
can be estimated by measuring the difference in elevation between two islands
and dividing by the difference in their ages (this method assumes the islands were
a similar size when they were active). Calculate how fast the Hawaiian Islands are
sinking, by using the ages and elevations of Maui and Nihoa.
13. Using the speed you calculated in the previous question (and ignoring possible
changes in sea level), when will the Big Island of Hawaii sink below the surface
of the ocean? Divide the current maximum elevation of the Big Island by the
rate you calculated in the previous question.
14. Now zoom out to ~4000 miles eye altitude and look at the chain of Hawaiian
Islands again. Notice the chain continues for thousands of miles up to Aleutian
Islands (between Alaska and Siberia). Examine the northernmost sunken
volcano (50 49 16.99N 167 16 36.12E) in this chain. Where was that volcano
located when it was still active, erupting, and above the surface of the ocean?
a. 50 49 16.99N 167 16 36.12E
b 52 31 48.72N 166 25 43.14W
c. 27 45 49.27N 177 10 08.75W
d. 19 28 15.23N 155 19 14.43W
15. The rock that most closely resembles the composition of continental crust
based on the description in the previous section is:
a. A
b. B
c. C
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d. D
Introductory Geology
Pl ate Tectonics
16. Based on the choice you made for question 15, what is the density of the rocks
that make up continental crust? Please give your answer in grams/milliliter.
17. The rock that most closely resembles the composition of oceanic crust based on
the description in the previous section is:
a. A
b. B
c. C
d. D
18. Based on the choice you made for question 17, what is the density of the rocks
that make up oceanic crust? Please give your answer in grams/milliliter.
19. Remember, because of isostasy the denser plate will be lower than the less
dense plate. If oceanic and continental crust collided, based on their densities
the __________ crust would sink below the ________crust.
a. continental; oceanic
b. oceanic; continental
20. According to the geothermal gradient, rocks buried 75 km beneath the surface
would normally be at what temperature?
At 75 km depth, rocks will be heated to about _______ degrees Celsius.
a. 1500
b. 1250
c. 1000
d. 750
21. According to the geothermal gradient, rocks at 500 degrees Celsius will be
buried how deep?
At 500 degrees Celsius, rocks will be buried to about _______ km depth.
a. 8
b. 12.5
c. 20
d. 27
22. What is the physical state of a dry mantle rock at point X?
a. Completely melted
b. Starting to melt
c. Completely solid
23. What happens when the lithosphere at point X is heated to 1500 °C?
a. No change
b. Starts to crystallize
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c. Starts to melt
Introductory Geology
Pl ate Tectonics
24. At what depth will the dry mantle rock at point X begin to melt if it is uplifted
closer to Earth’s surface and its temperature remains the same?
a. 35 km
b. 25 km
c. 18 km
d. 12 km
25. What would happen to the mantle rock at point X if water is added to it?
a. No change
b. Starts to crystallize
c. Starts to melt
26. Which of the following places represent a Wadati-Benioff zone?
a. 10°S, 110°W b. 0°, 0°
c. 15°S, 180°
d. 30°N, 75°E
27. The Wadati-Benioff zone is associated with which type of plate boundary?
a. Divergent
b. Convergent (Continent-Continent)
c. Convergent (Continent-Ocean or Ocean-Ocean) d. Transform
28. Examine the path of the river that feeds into and flows out of Quail Lake. What
direction is the North American plate moving in comparison to the Pacific Plate
at this location?
a. East
b. West
29. Given that San Francisco is located on the North American Plate and Los
Angles is located on the Pacific Plate, are these two cities getting closer together
or farther apart over time?
a. Closer
b. Farther
30. Type “15 19 48.78 S 75 12 03.41 W” into the Google Earth Search bar. What type
of tectonic plates are present?
a. Ocean- Ocean
b. Ocean- Continent
c. Continent- Continent
31. What type of plate tectonic boundary is present?
a. Transform
b. Convergent
c. Divergent
32. Type “6 21 49.68 S 29 35 37.87 E” into the Google Earth Search bar. What type
of process is going on at this location?
a. Seafloor spreading
b. Continental rifting
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c. Subduction
Introductory Geology
Pl ate Tectonics
33. What features would you expect to occur at this type of boundary?
a. Earthquakes and a trench
b. Volcanoes and a valley
c. Mountains and landslides
d. Earthquakes and offset rivers
34. Type “28 04 27.04N 86 55 26.84E” into the Google Earth Search bar. What
type of tectonic plates are present?
a. Ocean- Ocean
b. Ocean- Continent
c. Continent- Continent
35. What type of plate tectonic boundary is present?
a. Transform
b. Convergent
c. Divergent
36. Type “46 55 25.66 N 152 01 25.17 E” into the Google Earth Search bar. What
type of tectonic plates are present? Make sure to zoom out to get a good view
of the relevant features.
a. Ocean- Ocean
b. Ocean- Continent
c. Continent- Continent
37. What features would you expect to occur at this type of boundary?
a. Volcanos, earthquakes and a trench
b. Volcanoes and a linear valley
c. Mountains and landslides
d. Earthquakes and offset rivers
38. Type “43 41 07.81 N 128 16 56.29 W” into the Google Earth Search bar. What
type of tectonic plates are present? Hint- make sure to re-read the section on
plate boundaries before answering!
a. Ocean- Ocean
b. Ocean- Continent
c. Continent- Continent
39. What type of plate tectonic boundary is at this exact location?
a. Transform
b. Convergent
c. Divergent
40. This plate boundary isn’t as simple as the previous examples, meaning another
nearby plate boundary directly influences it. Zoom out and examine the area,
what other type of boundary is nearby?
a. Transform
b. Convergent
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c. Divergent
Introductory Geology
Pl ate Tectonics
41. Go back to the location in Google Earth that you examined for question 36
(46 55 25.66 N 152 01 25.17 E). Which of the three proposed plate tectonic
mechanisms would NOT occur at this location?
a. Slab pull
b. Ridge push
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c. Slab suction
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