//1.a. The world’s oceans are a distinctive feature of the Earth

Question 1

What are the 5 key oceans in the world

Answer 1

• Arctic ocean
• Pacific ocean
• Atlantic ocean
• Southern ocean
• Indian ocean

Question 2

What are the 4 main seas in the world

Answer 2

• Bering sea
• Gulf of Mexico
• Caribbean sea
• Mediterranean sea
• South China sea

Question 3

What is the structure of oceans

Answer 3

• edge of continent means the water deepens across a continental shelf
• at the continental slope, the angle increases
• the continental rise follows
• the deepest part of the ocean (abysasal plain), is then reached
• guyots are features of this plain (peaks that once rose above the ocean surface. Erosion has flattened the top and reduced the height)

Question 4

What is a rift valley

Answer 4

A rift valley is a valley formed by downfaulting between parallel faults

Question 5

What is a subduction zone

Answer 5

This is a zone where oceanic plate descends into the Earth’s mantle and is destroyed

Question 6

What is an oceanic trench

Answer 6

This is a narrow, deep depression on the ocean floor adjacent to a subduction zone

Question 7

What is the continental shelf

Answer 7

A wide flat margin with an average width of 70km and slope change of 2m per km

Question 8

What is the continental slope

Answer 8

A steep slope that descends to the abyssal plain. Angle change increased to 70m per km and average width is 16km

Question 9

What is the continetal rise

Answer 9

A wide and gently sloping zone

Question 10

What is the abyssal plain

Answer 10

The deepest part of the ocean that covers half the earth’s surface

Question 11

What is the seamount

Answer 11

Mountain chains that rise up from the abyssal plain. Some are over 3000m tall

Question 12

What are guyots

Answer 12

Peaks once above the water. They have eroded to leave a flat peak below the surface

Question 13

Explain the process of mid ocean ridges and rift valleys

Answer 13

• often mid ocean ridges cross the abyssal plains and produce transverse faults
• these faults run at right angles to the ridge and can be up to 1600km long
• in the centre of the ridge is the rift valley. Magma rises up from the mantle to push the plates apart

Question 14

What is palaomagnetism

Answer 14

This is the process by which scientists cab calculate how old the oceans are-traces of changes in the earth’s magnetic field in the allignment of magnetic minerals in igneous and sedimentary rock