SO461 Geological Oceanography

Spring 2006, Test 2

 

Short answer

4 @ 10 points

40

 

Longer answer

3 @ 20 points

60

 

Total

 

100

 

 

 

Short Answer: The questions should be answered with several sentences (no more than a short paragraph). You must answer four questions, and have a choice from five.

Longer Answer: These should clearly indicate understanding of the procedures and concepts involved, and use correct and appropriate terminology.

 

The exam is open book, which includes any notes permanently written in the book. No other references or calculators are allowed.

 

Budget your time. If you try to look up everything in the text book, you will run out of time.

 

 

Short Answer. Answer 4 of the 5 questions in this section, for 10 points each.

 

1. The diagram below shows two faults that appear to have similar geometries (A and A appear to the same feature, as do B and B. Are these right-lateral or left-lateral features? The two focal mechanisms appear to be different. Explain how this might be possible.

 

 

 

 

2. Discuss why this figure (6-9 of the textbook) is important.

 

 

3. Which of these 3 Ocean Drilling Program sites has the fastest sedimentation rates? Which would be the best for studying the start of the Pleistocene Ice Age, and why would you pick that site?

 

 

  

4. The diagram below shows a plate boundary, and the velocities between the two plates along the boundary. Given the geometry, what kind of a plate boundary do you think this is? How do we define plate motions, and what can you say about the plate motion between the two plates from the velocity pattern?

 


 

5. How can rocks that formed in the southern hemisphere during the Mesozoic be found in Alaska adjacent to rocks that formed in the northern hemisphere at roughly the same time?

 

Alaska is a collection of suspect terranes that have formed in other locations and migrated via plate tectonics to their current location.  The blocks include island arcs, oceanic plateaux, seamounts, and other features that were shallower than standard oceanic crust and would not be subducted; they then migrated north along the coast of North America before docking in Alaska.  Since the history of North America has included subduction along the west coast from the Pacific plates and its ancestors, much of the material in these suspect terranes has come a long way, from the SW, before arriving at North America.
 


Longer Answer. Answer all 3 questions in this section, for 20 points each.

 

The map below shows a diamond at the location of the large earthquake in Iran that occurred on 31 March 2006, with the focal mechanism below the map. The focal mechanisms for three other recent earthquakes in the region are also shown on the map. What kinds of faults are occurring in this region, what do they say about what is happening geologically, and is there a plate interaction here?

 

 

 

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The diagram below shows three plates (A, B, and C), and the velocities (mm/yr) in an absolute hot spot model. Complete the table. This is the triple junction in British Columbia; Plate A is the Pacific, Plate B is the Juan de Fuca (broadly defined), and Plate C is North America.

 

 

Plate Pair

Type of Boundary

Relative Velocity Rate

Evidence for type of boundary

A-B

 

 Ridge

 

 

B-C

 

 Trench

 

 

A-C

 

 Strike slip

 

 



 

 

The map below show a region with volcanoes, earthquakes, and two plate boundaries. Based on the map, and the graph showing earthquake depths by longitude on the map, discuss what you can infer about the plate tectonics of the region.

        What type(s) of plate boundaries are present, and how did you determine this?

        Would you expect there to more than one type of earthquake in the region?

        Would you expect igneous rocks to be created in this region? If so, list one type, and show where it would form.

        Would you expect metamorphic rocks to be created in this region? If so, list one type, and show where it would form.