SO461 Geological Oceanography

Fall 2004, Test 1

 

 

Definitions

10 @ 3points

30

 

Short answer

5 @ 5 points

25

 

Longer answer

3 @ 15 points

45

 

Total

 

100

 

 

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 10 of 12.

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

Longer Answer: These should clearly indicate understanding of the procedures and concepts involved, and should be well thought out with appropriate terms and details to support your answer.  

 

Note that on all three parts of the exam you have a choice of which questions to answer.

 

Budget your time.  If you try to look up everything in the text book, you will run out of time.  The three longer answers are worth almost half of the test; do not leave any of them blank.

 Definitions. Define 10 of these 12 terms.  For full credit insure that you complete describe the concept and its geological importance or significance.

 

1.      APW:

2.      Rad:

3.      Euler’s theorem:

4.      Paleolatitude:

5.      Sheeted dike:

6.      Ophiolite:

7.      Original horizontality:

8.      Mercalli scale:

9.      Absolute dating:

10.  S wave:

11.  Free air anomaly:

12.  Uniformitarianism

 

Short Answer.  Answer 5 of the 6 questions.  You do not have to use complete sentences, but must clearly indicate that you understand the concepts involved.

1.  Name five igneous rock types in this diagram, and state a plate tectonic environment where each forms.

 

 

Ultramafic

Mafic

Intermediate

Felsic

Extrusive

 

 

 

 

 

Intrusive

 

 

 

 

 

 

 

2.  How does rock deformation vary with depth in the earth’s crust?

 

3.  What can we determine from the variations in the intensity of the earth’s magnetic field?

 

4.  How can we use earthquakes waves to figure the thickness of the crust?

 

5.  How does isostasy explain the difference between the continents and the ocean basins?

 

6.  What do you find the most convincing evidence for plate tectonics, and why was Wegner’s continental drift idea so slow to catch on?

 

You must answer three of the four diagram questions. 

 

 

 

Mt. St. Helens shows increasing signs of activity.  The diagram below shows the results from one recent earthquake there.

oWhat can you say about the orientation of the fault plane for the earthquake? (be specific)

 

Note two possible fault planes, and we cannot pick which one was it.  Reading from the diagram, one strikes about N80E and dips 15 N, and the other strikes about N70E and dips about 85S.  (The actual values are N89W dip 12N, and N79E dip 78S).

 

oWhat type of fault caused the earthquake?

 

 

oWould an earthquake on this type of fault suggest danger of an eruption or that the mountain should be stable?

 

This earthquake actually occurred 5/18/1980, with Mb=4.7 and Ms=5.2, at a depth of 4 km. The sketch below shows the two possible geometries.  The normal fault geometry suggests that the intrusion of magma at depth is extending the crust laterally in a NS direction.  The earthquake in this database is located only to the nearest 1 km (0.01º), so we actually cannot be certain about its location in what became the caldera.

 

 

 

 

 

This diagram records the results from Sites 2005, 2006, and 2007 of the ocean drilling program.

  • Where is the fastest sedimentation rate—at which site, and during what period of time?
  • What happens at about 100 m into the section at Site 2007?  List several potential causes.
  • What happens at about 150 m into the section at Site 2005?  List several potential causes.
  • Which site would provide the best record of the KT (Cretaceous-Teritary) boundary?  Why?

 

 

 

Discuss what you see in this core from the northern Pacific, and what it tells you about the history of the site.

 

 

 

 

Do these earthquakes make a coherent picture for a plate boundary or boundaries?  Defend you answer.