Introduction to Earth Science

Introduction to Earth Science

Quiz 15 - Ocean Basins

1. Approximately how old is the oldest oceanic crust on the Earth today?
a. 6000 years
b. 200 thousand years
c. 2 million years
d. 180 million years
e. 2 billion years 

2. An example of a passive margin is:
a. the coast of California.
b. the coast of southern Alaska.
c. the East Coast of the United States.
d. Hawaii. 

Questions 3 to 9 refer to the image below that shows a map of the coastline and the seafloor in a region including Monterey Bay (between the coastal cities of Monterey and Santa Cruz) and Monterey Canyon (shown as MC). On the image, the arrow for letter E points to the coastline along Monterey Bay.

Map of bathymetry of Monterey Bay region

3. On the seafloor, Letter A is located on:
a. a continental rise.
b. a continental shelf.
c. a continental slope.
d. an abyssal plain.

4. The shelf break is located:
a. between letters A and B.
b. between letters B and C.
c. between letters C and D.
d. at letter E.
5. On the seafloor, Letter B is located on:
a. a continental rise.
b a continental shelf.
c. a continental slope.
d. an abyssal plain.
6. On the seafloor, Letter C is located on:
a. a continental rise.
b. a continental shelf.
c. a continental slope.
d. an abyssal plain.

7. What part of a continental margin consists of deep-sea fans created by turbidity currents?
a. continental shelf
b. continental rise
c. continental slope
d. abyssal plain

8. Monterey Canyon (shown as letters MC) is about twice the size and depth of the Grand Canyon in Arizona. Submarine landslides and turbidity currents move sediments down submarine canyons to be deposited mostly on the:
a. continental rise
b. continental shelf
c. continental slope
d. abyssal plain

9. An extensive flat section of the seafloor, Letter D is located on:
a. a continental rise.
b. a continental shelf.
c. a continental slope.
d. an abyssal plain.

10. Trenches are:
a. long, relatively narrow canyon-like features that run parallel to continental margins. 
b. the deepest parts of ocean basins. 
c. usually occur in the ocean along volcanic island chains.
d. All choices are correct.

11. An ancient submarine volcano that has a flat top (beveled by wave action before sinking into ocean depths and sea-level rising) and may lack fringing reefs is called:
a. an atoll.
b. a seamount.
c. a guyot.
d. a mid-ocean ridge. 

12. As new ocean crust forms along mid-ocean ridges, what happens to the older ocean crust?
a. Older crust moves away from spreading centers.
b. The older ocean crust cools and isostatically sinks deeper into the ocean basins.
c. The ocean crust is blanketed with layers of ocean sediments.
d. All choices are correct.

13. Black smokers and white smokers are features are:
a. hydrothermal vents associated with volcanic activity on the seafloor.
b. most common along the rift zones associated with mid-ocean ridges. 
c. host to biological communities that are supported by chemotrophic bacteria.
d. All choices are correct.

14. Pillow basalts occur where:
a. sediments accumulate in beds on the seafloor.
b. lava erupts and cools quickly on the seafloor on submarine volcanoes along mid-ocean ridges.
c. lava erupts from a volcano on an island arc chain. 
d. fringing reefs form around an ancient volcano. 

15. Where are the thinnest sediments generally found in deep ocean basins?
a. the mid-oceanic ridges.
b. trenches.
c. abyssal plains.
d. the continental rise.

16. Serpentinite is the State Rock of California. It occurs in abundance throughout the coast ranges of central and northern California. Serpentinite is a rock formed from:
a. the accumulation of the remains of ancient sea snakes.
b. a rock formed by the metamorphic alteration of ocean crustal rocks (basalt and gabbro) by exposure to seawater seeping into the ocean crust over time.
c. a rock formed from the accumulation of undersea landslide deposits.
d. All choices are correct.

17. As old ocean crust is destroyed in subduction zones, new continental crust forms as a result of:
a. water and gases released by increasing heat and pressure helps to melt some of the old ocean crust.
b. low-temperature felsic minerals melt first and migrate upward, forming volcanoes and new continental crust.
c. high-temperature mafic minerals are concentrated in the old ocean crust that sinks back into the mantle.
d. All choices are correct.

18. Iron-manganese nodules are considered to be: 
a. hydrogenous sediments.
b. lithogenous sediments.
c. biogenous sediments.
d. cosmogenous sediment.

19. A turbidite is a kind of rock formed from:
a. sediments deposited by an underwater landslide on a deep-sea fan.
b. sediment deposited around a shallow water coral reef.
c. sediment deposited along a beach near a river delta.
d. sediment that accumulates from the underwater rain of pelagic biogenous sediments.

20. Which is NOT a biogenous sediment?
a. calcareous oozes
b. siliceous oozes
c. coral reef deposits
d. quartz beach sand

21. If you find a rock that was part of an ancient coral reef, you know that the rock must have formed in:
a. cold, deep water.
b. turbid waters, such as near a river delta.
c. cool, clear, shallow polar water.
d. warm, clear, shallow tropical water. 

22. Which type of seafloor sediment (typically soft and mushy) consists mostly of the shells and skeletal remains of small (microscopic) organisms?
a. coquina
b. ooze
c. shelf mud
d. reef sediments

23. Coccolithopores are single-cell plants that grow in the warmer upper layers of the ocean. Their remain accumulate on the seabed forming:
a. siliceous ooze.
b. calcareous ooze.
c. turbidites.
d. mudstone.

24. Diatoms are the most abundant form of plankton in the world oceans. Their remains accumulate on the seabed forming: 
a. siliceous ooze.
b. calcareous ooze.
c. turbidites.
d. limestone.

25. A siliceous sedimentary rock that forms from the accumulation of the remains diatoms and radiolarian on the seafloor is called:
a. chalk.
b. chert.
c. graywacke.
d. quartz sandstone.