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Lab 3 Plate Tectonics W19

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Laboratory Exercise 3: Investigating plate
boundaries using Google Earth
Introduction to Geolog y II: Earth’s Surface Processes
Name____________________
Score: _________/25
INTRODUCTION
This is a modified version of an exercise titled Investigating Plate Tectonics with Google
Earth (Pratt-Sitaula, 2012). A link to the original exercise and supporting material can
be found at the end of this document. In this investigation you will examine data sets of
topography (land elevation), bathymetry (ocean depth), volcano locations, earthquake
locations and depths, and ocean floor age to determine the location and attributes of
different tectonic plate boundaries. After looking at examples at each of the three types
of plate boundaries, you will then look at two regions more closely (the Pacific
Northwest of the USA and the Himalayan Mountains of Nepal and other parts of Asia).
We will be using Google Earth this week, so you should first complete the posted
pre-lab exercise before you begin this one.
LET’S GET STARTED
Open Google Earth, then look at this week’s module in Canvas and find the file labeled
plate tectonics exercise.kmz . Click on this, then click to download it (it should not
download into the Canvas screen, rather, you need to click on the “Download plate
tectonics exercise.kmz” text at the top of the page). You can then open it within Google
Earth Pro (it might automatically do this). You should see this file now located under
Temporary Places in the Places window on the left of the Google Earth screen. If any
of the boxes in this file have a checkmark beside them, uncheck them (by clicking once
on the box), as this data will just clutter your screen. We will just checkmark the box
next to the data when we need it, and uncheck it when we don’t. Now open the other
file in our Week 3 module titled GlobalTectonics.kmz. Download it and again uncheck
anything that may have a check mark beside it. Make sure that the little arrowhead next
to each of these files is pointing down so that you can see all of the folders within each
file (to make the arrowhead move, just click on it once). Below you will see a
screenshot of my window showing that the contents of the file “plate tectonics
exercise.kmz” is open (arrowhead down), whereas the “GlobalTectonics.kmz” file is
closed (arrowhead pointing left). All data is unchecked.
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Does your screen look like this? If so, you are ready to get started!
Part A: Divergent Plate Boundary (The Atlantic Ocean)
Under the Places window on the left, within the plate tectonics.kmz file, make the
Atlantic cross-section visible by opening the Cross-sections folder (arrowhead pointing
down by this folder), then checking the Atlantic box, and then by showing the elevation
profile (by clicking Edit in the menu at the top and select Show Elevation Profile). (If it is
flat, be sure to check the Terrain box on the Layers panel.) The profile should look
somewhat (although not exactly) like the following profile (the profile below is a bit more
detailed, less smooth):
Questions/Tasks:
A1. (1 point) On the cross-section above (not the one you made), mark the
transitions from continental crust to oceanic crust (Use what you know about plate
thickness. The actual sea level elevation of 0 does not necessarily tell you where the
edge of the continental crust is.) There should be two transitions, one for the transition
from the continental crust associated with Africa to the oceanic crust under the Atlantic
Ocean, and one from the continental crust associated with North America with the
oceanic crust associated with the Atlantic Ocean. Mark each with an X. (Note that you
can either type an X directly onto this image while in Word, or you can draw on a printed
copy, then take a photo of this profile or scan it, and upload this image with your lab
exercise).
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A2. (0.5 point) On the cross-section above, mark the plate boundary between the North
American and African plates by labeling “PB”. If you are unsure, you should consult
your textbook, Chapter 4, section 4.3 (Divergent Plate Boundaries and Seafloor
Spreading).
A3. (1 point) Under Places, in the Global Tectonics file, check/select the Earthquakes
file. Circles with an x in the center, of all different colors, should appear on the Earth
(and a key to the colors should also appear; depth is in kilometers). If it doesn’t, zoom
in a little or ask for some help! Now scroll around the Mid-Atlantic Ridge looking at the
earthquake data. What depth earthquakes occur along this plate boundary? (Give the
range, according to the legend. For example, if you see lots of red circles along the
Mid-Atlantic Ridge, you would write that the depths are mostly 101-200km.)
A4. (1 point) Explain why the Mid-Atlantic Ridge is higher in elevation than the seafloor
around it. You might consult your textbook for ideas!
A5. (1 point) At what rate (in mm/yr ) are each of the plates moving relative to this
boundary (the ridge)? To answer this, you will need to use the ocean floor age data and
the Ruler tool to determine this. First select/check the Age-of-Ocean-Floors.kmz data
under Places, in the plate tectonics exercise.kmz file (this set of data is better labeled
and easier to use than the Seafloor Age file in the Global Tectonics.kmz file) and wait
for it to load. Now select the spot in the center of the ridge (bright red) along the original
cross-section line on the map , select the ruler from the top menu and click on this
center. Now move the cursor out to the right or left side (east or west) to where it is
labeled 30 (this means that rock is 30 million years old) and click there. Make sure your
ruler units is in kilometers. Divide your length in kilometers by 30 to get a rate in
km/my. This is the same as in mm/yr. Be sure to show your work and your answer
below.
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A6. (2 points) In the table below, summarize the features and phenomena associated
with this divergent plate boundary:
Bathymetric
Earthquake depths Are there volcanic
Age of seafloor at
features (What is
(give range, then
features here? (yes the boundary (give
the range of
determine whether or no)
range of seafloor
elevations? What
they are shallow,
age closest to the
features do you
deep, or both)
boundary)
see?)
Part B: Convergent Plate Boundary (Sumatra)
Uncheck all the other features and now make the Sumatra cross-section visible and
Show the Elevation Profile. It should look somewhat like this one:
Questions/ Tasks
B1. (1 point) Check the Global Volcanism Program data. Find the volcanoes in the
profile above and mark the location on this profile with a V. Now mark the boundary
between the Indo-Australian and Eurasian plates on the profile above with a PB. Again,
you might consult with Chapter 4 of your textbook if you are having trouble deciding
where the boundary might be.
B2. (1 point) Under Places, in the Global Tectonics file, again check/select the
Earthquakes file. Describe how (in a sentence) the earthquake depths change from
southwest (in the ocean) to northeast (on land) in this region.
B3. (1 point) Check/turn on the Plate Convergence data in the plate tectonics
exercise.kmz file (you might want to unselect all the other data). What is the rate of
Indo-Australian Plate motion? (No need to calculate! The answer can be found directly
on the map, you will just need to zoom out and move around to find the white arrow with
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the velocity value near it. Be sure to include units!)
B4. (2 points) In the table below, summarize the features and phenomena associated
with this convergent plate boundary:
Bathymetry/
Earthquake depths
Are there
Age of seafloor at
topography features
(Give range, then volcanic features
the boundary
determine shallow, here? (yes or no) (give age closest to
deep or both)
boundary)
Part C: Transform Boundary (San Andreas Fault, California)
Type California into the Search Panel and fly there. (You might want to turn off the
seafloor age and any other data that makes your screen cluttered.) Now make sure that
the Continental Transform Fault path is visible (this is in the plate tectonics
exercise.kmz file). 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.
Questions
C1. (1 point) What type of earthquakes (shallow or deep) do you see here, associated
with transform faults? (You probably remember which data you need to select to answer
this question.)
C2. (1 point) Find another area in North America where there are transform fault lines
shown and describe where in North America that location is.
Part D. The Pacific Northwest
Make the Juan de Fuca cross-section (in the plate tectonics.kmz file) visible and Show
the Elevation Profile. It should look somewhat like this one:
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Questions
D1. (1 points) There are two different plate boundaries in the above profile (and in this
region). Of the three types of boundaries you just reviewed (divergent, convergent, and
transform) which two do you think are found in this profile?
D2. (3 points) Mark each of the two boundaries on the profile above with a “PB”, then
describe below why you chose those locations for these two plate boundaries (use the
features from the previous profiles that you studied):
D3. (1 point) What is the convergence rate between Juan de Fuca Plate and North
America? (No need to calculate….just make sure the Plate Convergence path is visible,
and move around to find the white arrow with a velocity value near it.) Be sure to
include units.
D4. (2 points) How quickly is new Juan de Fuca Plate crust being generated? (Do this
the same way that you calculated velocity in A5…remember to turn the Age-of-OceanFloors data back on and go from the youngest ricks on the ridge out to the 30 million
year old rocks to the left/west of the ridge on the profile.) Show your work below and
give your answer in km/yr (the number will be the same as mm/yr).
D5. (0.5 point) Hypothesize as to whether you think the Juan de Fuca Plate is getting
bigger, smaller, or staying the same size?
D6. (1 point) Now watch (and listen or read to my commentary on) the
Pacific_spreading.mov animation posted in our Week 3 module. Do you agree with
your hypothesis above after viewing this? Why or why not?
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Part E. The Himalayan Mountains
Make the Himalaya cross-section visible and Show the Elevation Profile. It should look
somewhat like the profile below:
Questions
E1. (0.5 point) You know from the reading that this is a continent-continent convergent
margin. Using the topography shown in the cross-section above, mark on the crosssection above where you think the plate boundary is. (PB)
E2. (1 point) Watch the animation IndiaAsiaCollision_EMVC2008.mov posted in our
Week 3 module, and read or listen to my commentary on it. Do you still agree with
where you located the plate boundary? If you have changed your thinking, show the
location of where you would put the boundary now with PB2, and explain why you did or
did not make changes to your location.
E3. (0.5 point) Under Places, in the Global Tectonics file, again check/select the
Earthquakes file. What depth earthquakes are associated with the Himalayan-Tibetan
region? Be sure to include units!
E3. (1 point) Although this is a convergent plate boundary, the profile (and the features
in Google Earth) may look different from the profile (and features) of the convergent
plate boundary shown in part B of this exercise (Sumatra region). What is a feature that
is similar between the two locations and what is a feature that is different?
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Nice work, you are finally done! That was a tough exercise, wasn’t it?
Reference:
Pratt-Sitaula, B. (2012). Investigating Plate Tectonics with Google Earth. Retrieved July
15, 2015 from
http://serc.carleton.edu/NAGTWorkshops/structure/SGT2012/activities/63925.html.
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