Chapter 11

Question 1

Ocean floor age

Answer 1

The youngest part of the Earth’s surface.

Question 2

Ocean mapping methods (2)

Answer 2

Sonar and geoids

Question 3

Sonar

Answer 3

Sound navigation and ranging

Question 4

Geoids

Answer 4

Idealized surface of oceans representing gravitational equipotential surfaces.
Geoid low = mass deficit
Geoid high = excess mass

Question 5

Passive continental margins

Answer 5

Change from continental crust to oceanic crust on the same tectonic plate.

Question 6

Active continental margins

Answer 6

Plate boundary where one plate subducts below another. Accretionary wedge formed as sediments are scrapped of plate.

Question 7

Deep-ocean basin features (3)

Answer 7

1. Trenches formed by subduction
2. Abyssal plains
3. Seamounts (extinct volcanoes)

Question 8

Seafloor features (5)

Answer 8

Continental margins, deep-ocean basins, oceanic ridges, coral reefs and atolls, sea-floor sediments

Question 9

Continental shelf

Answer 9

Flooded extension of the continent that is 0-1500 km wide (average of 80 km).

Question 10

Continental slope

Answer 10

Boundary between continental crust and oceanic crust formed by rifting as continents split apart. The average slope is 5°.

Question 11

Continental rise

Answer 11

Accumulation of sediments at base of a continental slope of around 0.3°. (EX: deep sea fans)

Question 12

Mid-ocean ridges

Answer 12

Location that is volcanic in origin where plate moves apart at a ridge crest through sea-floor spreading. As plates move away from the ridge, they cools and contracts and ocean gets deeper. 20% of the surface of the Earth (70,000 km long and 1000-4000 km wide)

Question 13

Mid-ocean ridges on land

Answer 13

When ocean basins close, the oceanic crust can be placed on land to form an ophiolite. Form volcanogenic massive sulfide (VMS) deposits.

Question 14

Coral reefs and atolls

Answer 14

Form as plates move away from mid-ocean ridges and as volcanoes become extinct. Growth can keep up with subsidence.

Question 15

Sea-floor sediment types (2)

Answer 15

Terrigenous and biogenous

Question 16

Sea-floor mining

Answer 16

Manganese nodules form on abyssal plains and
Massive sulfide deposits form at mid-ocean ridges.

Question 17

Terrigenous sediments

Answer 17

Sand sized particles that originated on the continents.

Question 18

Biogenous sediments

Answer 18

Shells and skeletons of plankton living near the surface of the ocean.