Assignment 2 Section B (15 points) updated 11 AM 10/6/06
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Deadline: Tuesday, October 10, 2006, 11 PM
You participate in an oceanographic research cruise in the Indian Ocean from Jakarta, Indonesia (approximately 6˚S, 107˚E) to Mogadishu, Somalia (approximately 2˚N, 46˚E). At regular intervals you take a sample of ocean bottom material. Use an atlas and Figures 3.15 (p. 68) and 4.21 (p. 100) in Garrison and Fig. 3.5 in Sverdrup (below) to answer the following questions.
We can assign the structures we have observed on the sea floor as broad “Major Categories” of sea floor, and as smaller “Features” that reside on certain categories of sea floor. Some features are found only on certain categories and not on others.
Categories: active continental margin, passive continental margin, abyssal plain, mid-ocean ridge
Features found within certain categories: shelf, slope, rise, trench, canyon, abyssal hills, rift valley, guyot, seamount, island
On the designated route, you will pass over several “categories” of sea floor, each with its own set of “features.” The questions below ask you to identify the categories, assign them to type of crust, then list the features that you would expect to find on that category of sea floor. There is space for you to enter information for up to five categories of sea floor (Questions 1-5).
1A. (0.25 pts.) In the space below, list the first major category of sea floor you pass over on your cruise (i.e., as you leave Jakarta). Categories from which to select are listed above.
1B. (0.25 pts.) In the space below, identify whether this category of sea floor is underlain by oceanic (basaltic) crust or continental (granitic) crust.
1C. (0.5 pts.) In the space below, list all the relevant sea floor features that you might observe on this category of sea floor. More than one feature (or none) may be present within any category. Features from which to select are listed above.
2A. (0.25 pts.) In the space below, list the next major category of sea floor you pass over on your cruise (i.e., as you leave Jakarta). Categories from which to select are listed above.
2B. (0.25 pts.) In the space below, identify whether this category of sea floor is underlain by oceanic (basaltic) crust or continental (granitic) crust.
2C. (0.5 pts.) In the space below, list all the relevant sea floor features that you might observe on this category of sea floor. More than one feature (or none) may be present within any category. Features from which to select are listed above.
3A. (0.25 pts.) In the space below, list the next major category of sea floor you pass over on your cruise (i.e., as you leave Jakarta). Categories from which to select are listed above.
3B. (0.25 pts.) In the space below, identify whether this category of sea floor is underlain by oceanic (basaltic) crust or continental (granitic) crust.
3C. (0.5 pts.) In the space below, list all the relevant sea floor features that you might observe on this category of sea floor. More than one feature (or none) may be present within any category. Features from which to select are listed above.
4A. (0.25 pts.) In the space below, list the next major category of sea floor you pass over on your cruise (i.e., as you leave Jakarta). Categories from which to select are listed above.
4B. (0.25 pts.) In the space below, identify whether this category of sea floor is underlain by oceanic (basaltic) crust or continental (granitic) crust.
4C. (0.5 pts.) In the space below, list all the relevant sea floor features that you might observe on this category of sea floor. More than one feature (or none) may be present within any category. Features from which to select are listed above.
5A. (0.25 pts.) In the space below, list the next major category of sea floor you pass over on your cruise (i.e., as you leave Jakarta). Categories from which to select are listed above.
5B. (0.25 pts.) In the space below, identify whether this category of sea floor is underlain by oceanic (basaltic) crust or continental (granitic) crust.
5C. (0.5 pts.) In the space below, list all the relevant sea floor features that you might observe on this category of sea floor. More than one feature (or none) may be present within any category. Features from which to select are listed above.
6. (7 pts., 0.25 pts. each) Answer the following questions to compare and contrast two features in the Indian Ocean. Reunion Island (21˚S, 55˚E), south of your route, is the youngest, highest, and most active of a chain of volcanoes stretching northeastward away from the coast of Africa and Madagascar. Indonesia itself is also a volcanic island chain, ranging from about 5˚N, 95˚E to about 10˚S, 120˚E.
Match the following statements to the appropriate island chain by writing the word or initial "Reunion," "Indonesia," "Both," or "Neither" in the spaces provided.
6A. On continental crust
6B. On a destructive plate boundary
6C. Age increases, volcanic activity and elevation decrease from one end of chain to other
6D. On a transform fault
6E. Hot spot
6F. On oceanic crust
6G. On an active margin
6H. Not on a plate boundary
6I. Andesitic
6J. Age, volcanic activity, and elevation show no directional trend
6K. On a constructive plate boundary
6L. Explosive volcanic eruptions
6M. Basaltic
6N. Non-explosive volcanic eruptions
6O. On a passive margin
6P. Granitic
7. (1.5 pts., 0.25 pts. each) In the spaces provided below, name the plate on which each island chain in Question 6 resides, identify the compass direction in toward which each plate is moving, and identify the divergent boundary or boundaries where the motion of each plate is driven. Refer to an atlas and Figures 3.15 (p. 68) and 4.21 (p. 100) in Garrison.
7A. Reunion Islands: Plate name
7B. Reunion Islands: Direction plate is moving
7C. Reunion Islands: Name of divergent boundary (boundaries) for this plate
7D. Indonesian Islands: Plate name
7E. Indonesian Islands: Direction plate is moving
7F. Reunion Islands: Name of divergent boundary (boundaries) for this plate
8. (2.5 pts., 0.25 pts. each) In the spaces provided below, identify the key structural characteristics of the two types of continental margins.
8A. Type of continental margin observed in the eastern Indian Ocean
8B. Steepness of this type of continental margin
8C. Width of this type of continental margin
8D. Presence of a rise or trench
8E. Seismic activity along this type of continental margin
8F. Type of continental margin observed in the western Indian Ocean
8G. Steepness of this type of continental margin
8H. Width of this type of continental margin
8I. Presence of a rise or trench
8J. Seismic activity along this type of continental margin
9. (1 pt.) What happens to the elevation of the sea floor and the volcano when a new “hot spot” volcano is built on a moving oceanic plate? Explain the process and the structures involved. Be sure to identify & define the outer layers of the earth involved.
10. (1 pt.) Describe the origin of andesite, where it is found in the Indian Ocean region, and explain its explosive nature.