READING QUESTIONS: The Ocean Floor GEOL 131
NAME________________________
DUE: Tuesday, December 15th
Fall 2015
47 pts
All answers should be in your own words.
An Emerging Picture of the Ocean Floor (p. 346-348)
1. Define bathymetry. (2 pts) ___________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
2. Describe the basic operating principle of echo sounding. (4 pts) _____________________________
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
3. What is the main advantage of high-resolution multibeam sonar over sidescan sonar? (2 pts)
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
4. What percentage of the ocean floor has been mapped in detail? _______ %
5. List the three provinces of the ocean floor. (3 pts)
a. _______________________________________
b. _______________________________________
c. _______________________________________
Continental Margins (p. 348-350)
6. Label the three parts of a passive continental margin on the figure below. (3 pts)
7. Why are passive margins called passive? ________________________________________________
_________________________________________________________________________________
8. Passive margins develop when (2 pts) __________________________________________________
________________________________________________________________________________
9. The continental rise consists of (2 pts) __________________________________________________
________________________________________________________________________________
________________________________________________________________________________
10. EXTRA CREDIT: What is the average slope angle of continental shelves? ____________ degree
11. What plate tectonic setting do active continental margins develop in?
a.
b.
c.
d.
e.
Subduction zone
Divergent boundary
Rift zone
Continental collision zone
None of the above
12. How does an accretionary wedge form? (2 pts) __________________________________________
________________________________________________________________________________
________________________________________________________________________________
13. A subducting plate with a shallow subduction angle is more likely to exhibit subduction erosion than
one with a steep angle. TRUE or FALSE
Features of Deep-Ocean Basins (p. 350-353)
14. Fill in the blanks: Deep ocean trenches are sites of plate _______________________ where slabs of
_______________________ lithosphere _____________________ and plunge into the mantle. (3 pts)
15. Why are abyssal plains more extensive on the Atlantic Ocean floor than in the Pacific? (2 pts)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
16. Why are abyssal plains very flat? _______________________________________________________
17. How do guyots form? (3 pts) __________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
Anatomy of the Oceanic Ridge (p. 353-354)
18. What is the total length of the world’s oceanic ridge system? _________________ miles
19. What is the typical elevation of the crest of an oceanic ridge above the surrounding deep-ocean basin?
_____________ meters
20. Fill in the blanks: Oceanic ridges form where upwelling from the ____________ generates new
____________
______________. Oceanic ridges consist of layers and piles of newly formed
_________________ rocks that are buoyantly ___________________ by the _____ mantle rocks from
which they formed. (3 pts)
Oceanic Ridges and Seafloor Spreading (p. 354-356)
21. Oceanic ridges with slow spreading rates typically have (circle three answers): (3 pts)
a. No rift valley
b. A well-developed rift valley
c. A smooth topography
d. A rugged topography
e. Well-developed magma chambers
f. Poorly developed magma chambers
22. What is the primary reason why oceanic ridges are elevated? (2 pts) _____________________________
____________________________________________________________________________________
____________________________________________________________________________________
The Nature of Oceanic Crust (p. 356-358)
23. Examine figure 18 on page 357, then label the four layers of oceanic crust in the diagram below. (2 pts)
24. Explain how a sheeted dike complex forms (2 pts). __________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________