The Seafloor

Compare and contrast continental shelves and slopes.

Continental shelves are gently sloping, shallow sections of ocean floor just off the coast of continents. Continental slopes are the steeper inclines that occur between continental shelves and abyssal plains.

Mid-Ocean Ridge

Definition Area where new ocean floor is formed when lava erupts through cracks in Earth's crust. Usage New sea floor is formed along mid-ocean ridges.

Abyssal Plain

Definition Flat seafloor area from 4,000 meters to 6,000 meters below the ocean surface, formed by the deposition of sediments. Usage The abyssal plain stretched for miles deep below the surface of the ocean.

Continental Shelf

Definition Gradually sloping end of a continent that extends beneath the ocean. Usage The continental shelf of North America extends into the Pacific and Atlantic Oceans.

Trench

Definition Long, narrow, steep-sided depression in the seafloor formed where one crustal plate sinks beneath another. Usage The scientists used a remote controlled submarine to explore the deep ocean trench.

Continental Slope

Definition Ocean basin feature that dips steeply down from the continental shelf. Usage The ocean gets deeper very quickly along a continental slope.

What is a trench?

A long, narrow depression.

A mid-ocean ridge forms at what type of plate boundary? a. convergent b. divergent c. strike-slip d. parallel

B

Which of the following can occur next to the continental shelf? a. trench b. continental slope c. mid-ocean ridge d. all of the above

B.

____ are formed when one crustal plate is forced under another. a. Rift zones b. Trenches c. Mid-ocean ridges d. Continental shelves

B.

A mid-ocean ridge is formed from ____. a. abyssal plains b. the continental shelf c. lava d. a trench

C.

Sediment tends to build up in the a. Continental shelf b. Continental slope c. Abyssal plain d. Oceanic ridge

C.

Why aren't mineral deposits harvested from deep water?

Currently it is too difficult and expensive to harvest minerals from deep water. Technology is being developed to exploit these resources.

A continental shelf is characterized by all of the following EXCEPT: a. Abundant life b. Shallow water c. High amounts of sunlight d. High sediment build-up

D.

Trenches occur at divergent plate boundaries. True or False

False

In the image below, each circle is labeling a specific feature on the sea floor. Included is a list of five features of the seafloor labeled A through E. Working from left to right, identify the feature that each circle is identifying using the letters provided. A. abyssal plain B. continental shelf C. continental slope D. ocean trench E. mid-ocean ridge

Left to right: B, C, A, E, D, A, C, B

What is the difference between mid-ocean ridges and trenches?

Mid-ocean ridges occur at divergent plate boundaries. Trenches occur at convergent plate boundaries.

What mineral resources can be harvested from the continental shelf?

Sand and gravel for construction as well as diamonds and gold are mined from continental shelves.

What occurs at mid-ocean ridges?

Sea floor spreading occurs at mid-ocean ridges.

What occurs at the Juan del Fueca Ridge? (site 2)

The Juan del Fueca Ridge has at least four major, high temperature vent fields.

Describe the abyssal plain.

The abyssal plains are formed by thick layers of sediment. The sediment comes from the remains of organisms that died above and sank.

Of the three ocean basin zones (continental shelf, continental slope, abyssal plain) which has the greatest diversity of life and which is deepest?

The continental shelf has the greatest diversity of life because it gets the most sunlight. The deepest zone is the abyssal plain.

What evidence first supported the theory of seafloor spreading? (site 1)

The evidence that first supported the theory of seafloor spreading was when scientists found vents.

Occur at underwater subduction zones

Trenches

How are ocean trenches formed?

Trenches occur at convergent plate boundaries. The deep trenches occur where one plate is being subducted under another.

Magma from Earth's interior oozes from the cracks at mid-ocean ridges. True or False

True