Homework1-Part E (1)
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Worcester Polytechnic Institute *
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Course
2341
Subject
Geology
Date
Feb 20, 2024
Type
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7
Uploaded by MateEchidnaMaster1964
Part E: Investigating Plate Tectonics through Google Earth (38 pts)
Your task:
In this investigation you will examine data sets of topography, bathymetry (ocean
depth), volcano location, earthquake location, and ocean floor age to determine the location and
attributes of different plate tectonic boundaries. After looking at global plate tectonics, you will
look at our study regions more closely.
Tips
•
Please refer to “google earth tip sheet” for basic features and functions of google earth
•
When you bring files into Google Earth, make sure you save them to My Places and then
File
±
Save
±
Save My Places. That way if Google Earth crashes, everything will reload
automatically when you restart.
•
You should uncheck data sets that you are not using for a given question because they
may interfere with each other (particularly the Age-of-Ocean-Floor).
•
Earthquakes and volcanoes will not show up until you are somewhat zoomed in. You will
probably find that an eye altitude of 4000-5000km is best for balancing view scope with
data visibility.
a. Atlantic Ocean
Double-click plate tectonics exercise part 1.kmz to open it in Google Earth (don’t load plate
tectonics exercise part2.kmz yet or leave it not visible)
Make the Atlantic cross-section visible (located in the Cross-sections folder) and Show the
Elevation Profile (by first selecting or highlighting the Atlantic cross-section under “Places”
panel on the left, and then right clicking it and choosing “Show the Elevation Profile”… on Mac
you will need to “control-click” instead of right click).
1. On the cross-section, mark the transitions from continental crust to oceanic crust
(Use what
you know about plate thickness. The actual sea level line does not necessarily tell you where
the edge of the continental crust is.)
2. Mark the plate boundary between North American and African plates.
3. Using earthquake, bathymetry, and ocean floor age data, describe the lines of evidence that support
the location you have chosen for the plate boundary.
We know that the plate boundary between the north American and african plates are located at
the mid atlantic ridge, which is the highest point in between the two continents, which is the
location I selected.
4. What type of earthquake (shallow or deep) occurs along the plate boundary?
Shallow earthquakes, due to it being in a subduction zone.
5. Why does the plate boundary have an elevated profile (i.e. why the mid ocean ridge?)
(
Consider density and temperature)
It has a elevated profile because of the process of seafloor spreading. At
divergent boundaries tectonic plates are moving away from each other, causing
magma to rise, where pressure is lowered and rock melts to form new land.
6. What rate (in mm/yr ) are each of the plates moving relative to the boundary?
(You will need
to use the ocean floor age data and the Ruler tool to determine this)
5.02*10^8 / 30*10^6 = 16.73mm / year
7. What type of plate boundary is illustrated here?
Divergent plate boundary
8. Name three other places in the oceans where you observe the same types of boundary:
East pacific rise, Mid indian ridge, Arctic mid ocean ridge
b. Sumatra
Make the Sumatra cross-section visible and Show the Elevation Profile.
9. Mark the boundary between the Indo-Australian and Eurasian plates at the Earth’s surface.
Mark the location of volcanoes.
10. Using earthquake, bathymetry, and ocean floor age data, describe the lines of evidence that
support the location you have chosen for the plate boundary.
This location was chosen due to the sharp drop in elevation, where we know the
plate boundary should be. Also looking at the ocean floor age data the dates get
younger all up until that point, signifying it is where plate first formed. Most
earthquakes/volcanoes are also around that region, signifying even more that this is
the plate boundary of the subduction zone.
11. On the cross-section, mark in the approximate location of the earthquakes (horizontally and
vertically). What are these earthquake locations demarcating?
The red dots are where earthquakes have occured in the past, at the subduction zone
earthquake focii demarcates the subducting plate from the overriding plate.
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12. What is the rate of Indo-Australian Plate motion?
(this can be found directly from the Plate
Convergence data)
3.5 to 3.7cm per year
13. What type of plate boundary is it?
Convergent Boundary
14. Where else on the globe do you observe the same types of boundaries?
Nazca plate boundary, Mariana trench
c. California
Zoom in on California (there is no cross-section, just make sure that the Continental Transform
Fault path is visible).
15. The transform fault that is shown here is the famous San Andreas Fault that separates the
Pacific Plate from North American Plate in this area. What type of earthquakes (shallow or
deep) are associated with transform faults?
Transformation faults are often associated with shallow earthquakes.
d. Pacific Northwest
Make the Juan de Fuca cross-section visible and Show the Elevation Profile.
16. Based on what
you determined in the first two sections, what type of plate boundaries do you see represented
here? Mark where you think they are on the cross-section. What is your evidence for each?
The boundary represented here is a convergent boundary, juan de fuca trench is the deep
zone where convergence occurs, and subduction is evident in the cross section.
17. If the first two sections showed more “typical” plate boundaries, what characteristics of this
area seem unusual?
This area may seem unsusal since the juan de fuca plate is relatively small, and its
subduction is taking place at a very slow rate compared to other subduction zones.
18. The convergence rate between Juan de Fuca Plate and North America? (make sure Plate
Convergence path is visible)
How quickly is new Juan de Fuca Plate crust being generated? (same way you did in #6) Do
you think the plate is getting bigger, smaller, staying the same, or cannot be determined?
The new crust forming helps the juan de fuca plate maintain its size despite subduction due.
Convergence Rate is about 2.5cm / year.
19. Now watch the Pacific_spreading.mov animation that came in your zipped file. How would
you answer #18 now?
New crust forming helps the juan de fuca plate maintain it size despite subduction.
e. Himalaya
Make the Himalaya cross-section visible and Show the Elevation Profile.
20. You know from the reading that this is a continent-continent convergent margin. Using
topography, mark on the cross-section where you think the plate boundary is.
21. Watch the animation IndiaAsiaCollision_EMVC2008.mov. Do you still agree with where
you located the plate boundary?
Yes I believe that the video is trying to show to me that the boundaries are closer
in land around where the himalayan mountains are.
22. What has been the evolution of this plate boundary over the last 60 million years?
Over the last 60 million years the plates collided and the Himalyian mountain range formed as a
result of this collision.
23. Given that you know the major driving force behind plate tectonics is the downward pull of
descending plates, how do you explain that India is still colliding with Asia at over 40mm/yr?
What is keeping it going?
(it may help to zoom out and consider the large tectonic plate that
India is part of. Make part2.kmz visible to see plate boundaries.)
India is still colliding with asia at over 40mm/yr. We know this since the indian plate is
moving northward at around 50mm.year, this movement is what is causing the himalayas to
continue rising.
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24. What depth of earthquakes are associated with the Himalayan-Tibetan region?
Shallow earthquakes are associated with the Himalayan Tibetan region.
f. Earthquakes in our study region
Make sure the part2.kmz file is visible.
25. Using the Earthquake data (which includes Mag 6 since 2000 and about half a year of smaller
quakes), which type of plate boundaries are associated with bigger earthquakes and more
numerous earthquakes?
Transform boundaries, and subduction zones experience powerful seismic events.
Subduction zones often produce larger earthquakes but transform boundaries can as
well
.
26. Would you pick out either of our two case regions (Pacific Northwest and Himalaya) as
being particularly seismically active based on the last decade of earthquakes?
The pacific northwest is alot more seismically active based on the last decades of
earthquakes.