The ocean floor

Question 1

How much of the earth is covered by water?

Answer 1

Nearly 71%

Question 2

What are the 4 main ocean basins and their basic characteristics?

Answer 2

1. Pacific: largest (50% of total ocean) and deepest (3940 meters).
2. Atlantic: half size of pacific and narrower
3. Indian: slightly smaller than atlantic and entirely in southern hemisphere.
4. Arctic: 7% size of pacific and very shallow.

Question 3

What is Bathymetry?

Answer 3

Measurement of the ocean depths and charting of the shape or topography of the ocean floor.

Question 4

What is sonar?

Answer 4

Sonar (echo sounding) uses transmits sound towards the ocean’s floor and listens to echos. The time it takes to wait for the echo tells you the depth.

Question 5

How are satellites used in ocean floor mapping?

Answer 5

Ocean depth varies slighly with the mountains and valleys below due to gravitational effects. Satellites bounce microwaves off the ocean to measure its height precisely (within 3-6 cm) to determine tthe shape of the sea floor.

Question 6

What are the 3 ocean floor regions?

Answer 6

1. Continental margins
2. Ocean basin floors
3. Mid-ocean ridge

Question 7

What is a continental margin and what are its components?

Answer 7

A zone of transition between a continent and and ocean basin floor. Listed from continent to basin:

• Continental shelf: very gently sloping submerged section of the continent.
• Continental slope: possibly steep transition from continental to oceanic crust. Could be cut with deep submarine canyons.
• Continental rise: more gradual incline after the continental slope that leads into the basin.

Question 8

What is a ocean basin and what are its components?

Answer 8

Region between margin and ridge representing about 30% of the earths surface. Region includes:

• Deep-ocean trenches: where one plate descends beneath another.
• Abyssal Plains: Extremely flat areas created by sediment deposits.
• Seamounts: submerged volcano peaks
• Islands: volcano peaks that reach the surface.
• Guyots: islands that have disappeared/sunk due to erosion or the ocean plate moving the island away from its hotspot or ridge.

Question 9

What is a mi-ocean ridge and what are its components/features?

Answer 9

Found near center of ocean basins, it is a interconnected system of underwater mountains that have developed on newly formed crust. Not really a “ridge” as this area can be very wide (1000 to 4000 km wide).

• Seafloor spreading: Divergent plate boundary where two plate are moving appart. New ocean floor is created.
• Hydrothermal Vents: mineral rich water heated by newly created crust which escapes from cracks into the water.