SO461 Geological Oceanography

Fall 2003, 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 the 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.

 

Note that on both the definitions and short answer 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.

 

Answers in red are not complete--just things you should consider.

 

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.      Coccolith:

3.      Euler’s theorem:

4.      Clastic sedimentary rock:

5.      Pillow basalt:

6.      Ophiolite:

7.      Original horizontality:

8.      Epicenter:

9.      Relative dating:

10.  S wave:

11.  Bouger 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.  Place five igneous rock types in this diagram, and state a plate tectonic environment where each forms.

 

	Ultramafic	Mafic	Intermediate	Felsic
Extrusive
Intrusive

 

 

2.  What are the two types of rock deformation, and how are they different?

  

3.  What can we determine from the orientations of the magnetic minerals (rather than the intensity of the field) within a rock?

 

4.  How does the velocity of seismic waves changes as you go deeper into the crust, and how could this fact be used to find the Moho?

  

5.  How do the two models of isostasy differ, and which type operates in the earth’s lithosphere?

 

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

 

You must answer this question.

 

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

 

Things to consider:

Layers 1,2,3, mantle

Latitudes implied by sediment

Above/below CCD

Thickness sediment

Parts of ophiolite missing?

 

You must answer this question.

 

 

 

On 25 Sept 2003, there were two earthquakes near Japan.  The times listed are UTC.

 

         hr  min   sec       lat     lon    depth   mb   Ms

PDE      19   50   8.00     42.17   143.72   33.0  8.0  8.0

 

         hr  min   sec       lat     lon    depth   mb   Ms

PDE      21    7  59.00     41.81   143.51   33.0  7.0  7.0

 

The diagram above shows the Harvard Quick CMT catalog solution for this earthquake.

 

• What appears to be the orientation of the fault plane for this event? Are the two earthquakes similar? Be very specific, and include any qualifications on your answer.

 

Harvard solutions.  Note two possible fault planes, and we cannot pick which one was it.  Based on the map at the end of the test, the shallow dip to the NW is the more likely.

 

  Mw = 8.3    mb = 8.0    Ms = 8.0   

  Fault plane:  strike=252    dip=11   slip=136

  Fault plane:  strike=25    dip=83   slip=82

  Mw = 7.3    mb = 7.0    Ms = 7.

  Fault plane:  strike=225    dip=20   slip=106

  Fault plane:  strike=29    dip=71   slip=84

 

• What do the mb and Ms numbers mean on the listing of the earthquake parameters?  How do the two quakes differ?

 

First had 10 times the motion, and 30 times the energy released.

 

• What type of fault do you think was responsible for the earthquakes, and in what kind of plate setting would you find this?

 

 

You must answer this question.

 

The diagram below shows the magnetic anomalies recorded at three locations in the Indian Ocean.  A time scale and distance scale are on the bottom.

 

• Locate any ridges.
• Locate and label three anomalies on each diagram.
• Where is the oldest crust?
• How do the spreading rates vary, and why would spreading rates vary if these were all produced by the same ridge?.  You should at least do a rough order of magnitude calculation to show that you know how this would be applied.

 

 

 

Additonal  notes on the Japan Earthquake. 

 

Previous Deadly Earthquakes in this Region

Date UTC	Magnitude	Fatalities	Damage
1952 March 4	8.6	31	31 killed, 72 injured; 713 houses destroyed, 5,980 damaged. 28 killed and warehouses destroyed at Kushiro. 3 killed and 309 houses destroyed at Kiratapu. 1,000 houses destroyed or damaged at Shiranuka and 400 schools collapsed at Sapporo. 10-foot tsunami.
1968 May 16	7.9	48	Damage estimate at 25 million USD.
1993 January 15	7.6	2	614 injured and substantial damage (VI JMA) at Kushiro, Hokkaido and Hachinohe, Honshu. Felt (V JMA) at Hiroo, Nemuro, Obihiro, Otaru and Urakawa; (IV JMA) at Hakodate and Tomakomai; (III JMA) at Sapporo, Hokkaido. Felt (IV JMA) at Aomori and Morioka; (III JMA) at Akita, Fukushima, Sendai, Tokyo and Yokohama, Honshu. Also felt (VII) on Shikotan and (VI) at Kurilsk, Kuril Islands. Landslides and subsidence occurred in the epicentral area.