SO461 Geological Oceanography

Spring 2003 Test 2








11 @ 3points



Short answer

4 @ 8 points



Longer answer

3 @ 15 points









Definitions: answer with no more than a single sentence. You should be complete and show you clearly understand the term. Note that you need only answer 11 of the 13.

Short Answer: The questions should be answered with several sentences (no more than a short paragraph). You must answer 4 of the 5 questions.

Longer Answer: These should clearly indicate understanding of the procedures and concepts involved, and you must answer all 3.


Note that on both the definitions and short answer you have a choice of which questions to answer.


Definitions. Define 11 of these 13 terms






        Stage pole:

        Foreacrc bulge:

        Indentation tectonics:

        Rift valley:


        Andean mountain belt

        Suspect terrane:

        Oceanic plateau:

        Subbottom profiler:

Short Answer. Answer 4 of the 5 questions in this section. You do not have to use complete sentences, but must clearly indicate that you understand the concepts involved.


1. What is the geologic feature show in this diagram, and how do the top and bottom parts of the figure differ?

2. The Dead Sea Rift is a left lateral fault that strikes north-south. Draw a sketch map to illustrate what this means. Then draw another sketch to show how the motion would vary along a transform fault and a strike-slip fault with the same geometry.


3. Sketch a destructive plate boundary.

                    Show where two different kind of metamorphic rock would form, and describe how the rocks would differ.

                    Show where two different kind of igneous rock would form, and describe how the rocks would differ.


4. This diagram shows the focal mechanism for a recent earthquake in northern Iraq, and the plate boundaries in the region. What kind of fault ruptured to produce the earthquake, what was its orientation, and how can you relate the fault to tectonic processes in the region?





5. The top diagram shows the earthquakes associated with a plate boundary, and the bottom diagram shows the earthquakes within the box plotted by longitude and the depth of the focus. What does the pattern of earthquakes tell you about this plate boundary?







Longer Answer. Answer all three of these questions.


1. This diagram shows the absolute velocities in the hotspot reference frame for two plates, with the vectors labeled. The rates are in mm/yr. The small diagram shows some islands, the plate boundary, and the two plates before the velocity vectors were added.

        What kind of boundary is depicted, and how do you know? (There are at least three very distinct lines of evidence, and you should cover two.)

        Compute the relative velocity between the two plates. Insure that your method is clear; you can estimate the numbers.

        How could you determine where the pole of rotation between the two plates was located?






2. This diagram shows three east-west magnetic profiles across a suspected ridge that runs north-south. All have the same scale. A magnetic anomaly scale at the bottom shows the times of the anomalies for the past 13 Ma.

                    Pick several anomalies and show how you would correlate the three profiles.

                    If it is present, show the location of the ridge crest on each diagram.

                    Which profile has the fastest spreading rate, how can you tell, and what would you estimate the rate to be?

                    Which profile is closest to the Euler pole about which the two plates are moving, and how do you know?

                    Which location on the three profiles has the oldest crust, and what would you estimate to be the age of that crust?




3. The diagram below shows a triple junction for three plates, with both a velocity diagram (in the absolute hot spot reference frame) and in map view.


                    What is the nature of the AB boundary, and how could you tell?

                    What is the nature of the BC boundary, and how could you tell?

                    What is the nature of the AC boundary, and how could you tell?

                    Is the triple junction stable? Are there any assumptions you must make to answer this question?

                    Will the triple junction migrate with respect to any of the plates?

                    Which pair of plates has the slowest relative motion at this triple junction, and how could you tell?