SO461 Geological Oceanography

Spring 2013 Test 1



4 @ 20 points



Short answer

4 @ 5 points








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.




Figure 1. The four magnetic anomaly profiles above 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, and 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.




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.




One profile has something unusual happening. Which one is it, and what do you think happened?





How do these profiles relate to the Euler pole for the two plates involved?


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.


Figure 3. The diagram above shows the focal mechanisms for selected earthquakes in a region that is about 1000 km across. The center of each symbol is approximately at the epicenter.


How many different groups of earthquakes and faults do you think occur in this region.


Show the likely orientation of the fault plane and the type of fault involved for each group of faults. Be specific and include numbers; list and defend any assumptions you make.


On the diagram, sketch a possible plate boundary or boundaries and indicate the plate motions suggested by the earthquake data.



Figure 4. Sketch a continental margin, showing characteristics of the continental and oceanic crust. How does the concept of isostasy relate to the diagram?








Figure 5. The map on the previous page shows a region, the location of an earthquake with its associated focal mechanisms, and a topographic profile through the epicenter of the earthquake.




         What kind of fault failed during this earthquake, and what is its orientation?



         Why did the topographic profile run in the direction it does? Would there be a better direction in which to orient it?




          Do you see anything in the topography which matches the orientation of the fault plane?




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


         Apparent polar wander:



         Richter versus Mercalli:

         Compare P wave velocities in water and rock: