Download Oceanography 101 Linda Khandro, MAT Homework 3: Plate

Oceanography 101
Linda Khandro, MAT
Homework 3: Plate Tectonics (20 points)
NAME:_____KEY_________________
Learning Outcomes: by the end of the homework students will be able to
 recognize and list the major tectonic plates of the earth’s crust
 describe the motions of these plates and the interactions that occur at plate boundaries
 discuss the relative age(s) of the seafloor
 determine the effects of seasonal changes on ocean life.
Exploring Plate Tectonics with the Jules Verne Voyager website:
I.
Introduction and Getting Started. Read all:
chttp://www.dpc.ucar.edu/VoyagerJr/JVV_Jr/help/helpoverview.html
II.
Click on Base Map, read all:
http://www.dpc.ucar.edu/VoyagerJr/JVV_Jr/help/helpmap.html
III.
Click on Add Features, click on Add Velocities, test and play with them all!
A. Note that you can zoom in for closer detail by clicking on a portion of the image (see
information at the Getting Started link) but you can also use your browser View function
(or use CTRL +) to make the actual map larger.
B. Note that with each change you make (changing either or both or all of the Base
Map, the Features, or the Velocities) you must click “Make Changes” before the new
map will load.
C. Upon opening the file below (where the action is!), the first map you see should be
the default Base Map called, “Face of the Earth and Relief”. If this is NOT what you see,
set the Base Map for “Face of the Earth and Relief” and click Make Changes.
IV.
Here is where the action is!
http://jules.unavco.org/VoyagerJr/Earth?submit.x=50&submit.y=10&base=facer&feature=nofea
t&fixplate=novel&veltype=model&legendPopup=yes&region=world_0_0&size=normal
V.
And here is the Assignment, starting with the Base Map above: (20 points: 1 per
question)
A. Add the Feature called Tectonic Plates.
1. Use your textbook map of tectonic plates to test yourself on the names of the 7
largest plates. List them here:
1
AFRICAN, SOUTH AMERICAN, NORTH AMERICAN, EURASIAN, ANTARCTIC,
INDO-AUSTRALIAN, NORTH AMERICAN
2. What is the name of the small plate that is found west of the US/Canada shoreline?
JUAN DE FUCA
B. Add the Velocities link called No-Net-Rotation.
Make sure that the button to the right of the Velocities selection is set for Model. Note that in
the upper left corner of the map there is a scale of velocities; the arrow indicates a speed of
50mm/year.
3. What is the direction of motion and velocity of that motion of the Pacific Plate?
NW; 50 mm/yr
4. What is the direction and velocity of the North American Plate in the vicinity of the
US/Canada Pacific Northwest?
SW; 25 mm/yr
5. The general motion of the North American plate is not the same everywhere on the
plate. It appears to be rotating. What is the rotation direction? Clockwise or
Counterclockwise?
Counterclockwise
6. What is the direction and velocity of the Indo-Australian Plate?
NE; 60 mm/yr
7. What is the direction and velocity of the African Plate?
NE; 30 mm/yr
8. Look at the mid-ocean ridge (divergent boundary or spreading ridge) that runs
through the Indian Ocean, separating the African plate from the Indo-Australian plate.
Now compare THAT mid-ocean ridge to the one in the mid-Atlantic. What distinguishes
these two spreading regions? Hint: look at the arrows of direction and velocity.
N Atlantic = divergent boundary with 2 plates moving away from each other
Mid-Indian = divergent with one plate moving faster than the other
9. When two plates move at different velocities, the faster one usually dominates the
boundary, regardless of the type of boundary (convergent, transform, or in this case,
divergent). At the divergent boundary separating the African from Indo-Australian plates,
which plate motion is faster? Explain how this could explain the oddity (or difference
between this boundary and that of the mid-Atlantic) of this seafloor spreading?
Indo-Australian plate velocity>African plate velocity
10. Which plate is bounded ONLY by divergent boundaries?
2
Antarctic
11. Describe the boundary and the plate motions between the Pacific and Nazca plates.
Include the direction and velocity of each.
Divergent: Pacific NW; 60 mm/yr. Nazca E-NW; 50-60 mm/yr
12. Go to this site: http://en.wikipedia.org/wiki/East_Pacific_Rise, for detailed
information about the East Pacific Rise. Go to the end of the last paragraph. There is a
feature of this divergent boundary that makes it different from all other divergent
boundaries. What is that feature?
This divergent boundary is the East Pacific Rise, the fastest of all spreading boundaries.
13. Describe the boundary and the plate motions between the North American and
Eurasian plates. Include the direction and velocity of each.
Divergent: N. Am Plate NW; 25 mm/yr. Eurasian NE; 25 mm/yr.
14. What is the overall or general motion of the Eurasian plate?
Clockwise
C. Change the Base Map to the one called Ocean Floor Age. Change the Velocities to No
Plate Velocities. Open the link called Legend.
15. What color represents the youngest seafloor rock? Oldest seafloor rock?
Youngest = dark red; oldest = dark blue
16. Where (on which plate) do we find the oldest seafloor rock on earth?
West side of Pacific plate
D. Add the Earthquakes feature.
17. What causes the dense concentration of earthquakes from Eastern Europe to
central China? Describe this in terms of plate boundary interactions.
Continent/continent convergence
18. Which 3 large plates are involved in this region?
African, Indo Australian, and Eurasian.
E. Scroll the Base Map options to see the SeaWiFS maps. SeaWiFS is a satellite that
measures many variables in Earth’s oceans- and land- life, along with reflectivity of sunlight.
The term “bio” here refers to the amount of plant-type life in the oceans and on land by
measuring the concentration of chlorophyll produced. This is also a measure of “primary
productivity”. The term “reflect” refers to the reflectivity of Earth’s surface by water, ice, snow,
soil, vegetation, etc. Both of these variables change with the seasons.
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Change your base map to SeaWiFS Bio Jan-Mar. Open the link called Legend and use the
Chlorophyll value (you might have to do this repeatedly).
19. Estimate the amount of “primary productivity” in milligrams per cubic meter (mg/m3)
in the ocean at about the latitude of Ireland in the North Atlantic.
0.5 – 2.0 mg/m3
F. Test all the SeaWiFS Bio base maps to determine at which period of time you see the
greatest primary productivity.
July - Sept
20. Where in the northern hemisphere oceans do you see the greatest amount of
primary productivity at this time? Estimate the amount.
North coast of Russia/Siberia: 5.0 – 20.0 mg/m3
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