SO461 Geological Oceanography

Fall 2013 Test 1

 

Diagrams

4 @ 20 points

80

 

Short answer

4 @ 5 points

20

 

Total

 

100

 

 

Authorized reference:

  1. This test will be open book.Students can use their own copy of the textbook, with any notes they have permanently written in it.No papers can be attached to the text, and class notes and handouts will not be allowed. Books will not be shared during the exam.
  2. Calculators will not be allowed.For the calculations, you may set it up and leave the answer in terms of a sum, product, or quotient, or you can make reason simplifications to get a rough idea of the answer.

 

Diagrams: 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. You must answer four of the five questions.

 

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

 

Budget your time.If you try to look up everything in the text book, you will run out of time.Do not leave anything blank, and note that I am looking for an understanding of the important concepts and appropriate use to terminology.An answer that does this will get more credit than finding and copying a sentence in the book that includes the word asked for.

 

All work on this exam is individual.You may not any materials (books, notes, computers) other than your personal copy of the text, and you may not use IM, texting, talking, or any other means to communicate with other individuals.If you are caught with an electronic device that is not turned off and inaccessible you will get a 0 on the exam.

 

 


Short Answer:Briefly answer 4 of the following 5 questions.Your answer must explain what the term means and why it is important.

 

         MORB:

         Bouger gravity anomaly: gravity anomaly, corrected for the height at which it is measured and the attraction of terrain.

         Richter versus Mercalli:

         Compare P wave velocities in water and rock:

         Superposition:


 

 


 

Figure 1.The four magnetic anomaly profiles on the previous page were acquired in the same region, and all have the same horizontal scales (in km) and vertical scales (in nannoteslas).The time diagram on the bottom shows the durations of normal and reversed periods during the last 12 Ma; its horizontal scale may not correspond with any of the profiles above.The major anomalies are labeled above the profile.

 

What are these magnetic profiles actually measuring?Be explicit.

 

 

 

Why are the black and white intervals of different lengths?

 

 

 

 

 

Label at least five anomalies on each on the longer two profiles with your estimate of the age in millions of years or the anomaly names.For the bottom two profiles label at least two anomalies.

 

 

On each profile, mark the location or the ridge or indicate the direction in which you would look to find the ridge that created this seafloor.

 

 

 

 

How does the spreading rate vary for each profile?For one profile, show how you would calculate it, and then indicate whether the other profiles would have faster or slower spreading rates.

 

 

 

There is no anomaly 1A, but there is a 2A, 3A, and 4A.Why?

 

 

 


 

Figure 2.The diagram on the previous page shows a sequence of rocks that you found while walking through the scenic mountains of Oman on your graduation leave.The thickness scale is in meters.Discuss what you can infer about the geologic history from these rocks.For full credit you should have something to say about each rock layer, and a brief summary/conclusion.

 

How would your conclusions change if the top layer was a red clay?If it were a siliceous ooze?



 

Figure 3A.Sketch a continental margin, showing characteristics of the continental and oceanic crust.How does the concept of isostasy relate to the diagram?

 

 

  

Figure 3B.What are the units for the two axes on this graph, and how did Mohorovicic use this data to get a boundary named for himself?

 


 

 

 

 


 

Figure 4A.The diagram above shows the focal mechanism and location from a magnitude 7.7 earthquake that occurred on September24, 2013 in Pakistan.

 

Looking just at the focal mechanism, what kind of fault ruptured, and what can you say about the faultís orientation?

 

 

Looking at the orientation of the mountains around the epicenter, can you improve on your analysis of the fault orientation?

 

 

 

 

 

Figure 4B.This map showsthe location of the earthquake (in red) and the other focal mechanisms from the last 25 years.Based on this, what do you think is the primary orientation of the faults in this region.

 

 

 

There are two anomalous earthquakes.What can you say about the orientation and type of fault responsible for them?