Chapter 13: The Ocean Floor

Question 1

How much of the earth’s surface is covered with bodies of water?

Answer 1

71%

Question 2

How much of the earth is covered with continents and islands?

Answer 2

29%

Question 3

What are the nicknames for the Northern and Southern Hemisphere?

Answer 3

N= Land Hemisphere
S= Water Hemisphere

Question 4

What is Oceanography?

Answer 4

interdisciplinary study of the oceans that draws on geology, biology, chemistry, and physics

Question 5

The four basic ocean basins?

Answer 5

1) Pacific (largest and deepest)
2) Atlantic (half size of Pacific)
3) Indian (southern hem ocean… smaller than Atlantic)
4) Arctic (only 7% size of Pacific)

Question 6

What is the measurement of the ocean depths and the charging of the shape or topography of the ocean floor?

Answer 6

Bathymetry

Question 7

What is a Echo Sounder?

Answer 7

also known as a sonar.

• invented in 1920’s
• instrument measuring water depth
• reflects sound from ocean floor, measures time required for acoustic wave to travel from ship to the sea floor and back

Question 8

When was the Sidescan Sonar developed?

Answer 8

after WWII

Question 9

What is a Multibeam Sonar?

Answer 9

improvement from sidescan sonar and DOES provide depth.

Question 10

What device bounces microwaves off sea surface from space to measure surface irregularities present due to gravity?

Answer 10

Radar altimeter

Question 11

What is a Passive Continental Margin?

Answer 11

Found along coastal areas that surround Atlantic.

Margins that are not associated w/ tectonic plate boundaries
-experience very little volcansim and few earthquakes

Question 12

The five components to Passive Continental Margins?

Answer 12

1) Continental Shelf
2) Continental Slope
3) Submarine Canyons
4) Turbidity Currents
5) Continental Rise

Question 13

What is a Continental Shelf?

Answer 13

A flooded extension of the continent.

• varies greatly in width
• gentle sloping
• contains rich oil and mineral deposits
• consist thick deposits of shallow-water sediments

Question 14

What is a Continental Slope?

Answer 14

Marks seaward edge of the continental shelf.

• relatively steep
• boundary between continental crust and oceanic crust

Question 15

What is a Submarine Canyon?

Answer 15

A deep, steep-sided valleys cut into continental slop by rivers.

• seaward extensions of river valleys that once were above sea level, now flooded by ocean
• appear to have further eroded by turbidity currents

Question 16

What is a Turbidity Current?

Answer 16

A downslope movement of dense, sediment-laden water; type of mass wasting event

• underwater landslides
• deposits formed from this mass wasting is called turbidtides

Question 17

What is Continental Rise?

Answer 17

Composed of thick sediment.

• located at base of continental slope
• found in regions of subduction trenches are absent
• continental merges into a more gradual incline (continental rise)

Question 18

What is an Active Continental Margin?

Answer 18

Accumulations of deformed sediments and scraps of ocean crust from accretionary wedges.

• located primary around Pacific “ring of fire”
• occurs when continental slope descends abruptly into a deep-ocean trench

Question 19

Bathymetry reflects what?

Answer 19

Tectonic plate boundaries

Question 20

Mid-ocean ridges mark what?

Answer 20

divergent boundaries

Question 21

Oceanic transform faults trace what?

Answer 21

strike-slip boundaries

Question 22

Deep-ocean trenches signify what?

Answer 22

convergent boundaries

Question 23

Deep-Ocean Trenches

Answer 23

• Long, narrow features
• Created due to subduction moving lithoshoeric plates plunge into mantle
• Trenches are DEEPEST part of ocean
• Associated w/ volcanic activity

Question 24

Mariana Trench

Answer 24

Deepest location anywhere in the ocean.

Result of 2 oceanic plates colliding together. (subduction)

Question 25

The Challenger Deep Canyon

Answer 25

Named after HMS Challenger a British Royal Navy Ship.

-the deepest point within the deepest trench

Question 26

What is a Abyssal Plain?

Answer 26

A deep, flat ocean feature
-most level place on earth
-thick layer of sediment
-found in ALL oceans
EX: abyssal plain off coast of Argentina

Question 27

Seamount

Answer 27

An isolated submarine volcano that rises at least 1,000 m above the ocean floor.

• many grow large enough to become an island
• may erode to from flat-topped seamounts called guyots or tablemounts

Question 28

What is a Guyot?

Answer 28

a submerged flat-topped seamount (“gee-oh”)

Question 29

Oceans Preserve what?

Answer 29

Hot-spot sediments.
-volcanoes for islands over hot spots
EX: Hawaiian Islands and Emperor Seamount Chain

Question 30

A ring of coral reef that builds up to surround a central lagoon is called what?

Answer 30

Coral Atoll

Question 31

What is the Mid-Ocean Ridge?

Answer 31

An elevated ridge in the center of each ocean w/ faulting where new sea floor is always forming.
-Longest topographic feature on Earth! (not narrow)

Question 32

What are some sediment sources for the ocean floor?

Answer 32

Turbidity currents (underwater landslides)
Sediment that slowly settles to the bottom from above.
(thickness of sediment will vary)

Question 33

Types of seafloor sediments?

Answer 33

1) Terrigenous (land-based) sediments (material weathered from continents)
2) Biogenous Sediment (shells and skeletons of marine animals and plants)
3 Hydrogenous Sediment (minerals that crystallize directly from seawater)

Question 34

How much of the world salt is extracted from seawater?

Answer 34

30%