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GEOL 1033, General Oceanography
Q9
REVISED Study Question Set 9 (Lesson 11)
Question and Answer Sheet:
Name: __________________________
ID #: ____________________
1. About what percent of the Atlantic Ocean floor does the Mid-Atlantic Ridge occupy?
______%
2. What is the approximate average depth of the crest of the Mid-Atlantic Ridge? ______________
3. Abyssal plains are, on average, how much deeper than mid-ocean ridges? _________________
4. What kind of faulted-bounded valley is the axial rift at the crest of an ocean ridge? ___________
5. Approximately how wide is the axial rift valley?
_________________________
6. How many normal faults should a graben have? 1, 2, 3, 4, 5, 10?
________
7. What type of igneous rock forms after magma intrudes fractures in the crest of a mid-ocean
ridge, cools, and crystallizes?
_________________________
8. When this molten rock extrudes onto the seafloor as lava, what shape does it develop when it
cools?
_________________________
9. Due to thermal contraction upon cooling and isostacy, volcanic mountains, such as seamounts
and tablemounts on the seafloor, eventually slowly
_________________________.
10. The axes of mid-ocean ridges are laterally offset by what kind of fractures?
__________________ ________________(2 words)
11. Can adjacent sides of these fractures (see question above) be either moving in the same or
opposite directions, depending where you are along the fracture?
("yes" or "no") __________
12. What kind of earthquake occurs at mid-ocean ridges?
_________________________
13. What kind of earthquake occurs along transform faults?
_________________________
14. How deep is a shallow-focus earthquake?
_________________________
15. In the same ocean basin, which would be older: the "crest" of the mid-ocean ridge or the
adjacent "abyssal plains"? (Print the correct emphasized term at right.) ____________________
16. How old is the oldest seafloor sediment or rock?
_________________________
17. Which should have a much thicker surface layer of sediments: the "crest" of a mid-ocean ridge
or the adjacent "abyssal plain"? (Print the correct emphasized term at right.) _________________
18. Approximately how thick are the sediments, on average, in abyssal plains near the margins of
continental rises? (Print the correct emphasized term at right.) _________________________
19. Do turbidites occur in abyssal plain sediments?
("yes" or "no")
_____________
20. In abyssal-hills regions of the seafloor, what are usually found in the valleys between the hills?
_________________________