5.4 Plate Margins & Magma Plumes

Question 1

Define Constructive Plate Margin

Answer 1

2 plates move away from each other (divergent)

Question 2

Define Destructive Plate Margin

Answer 2

2 plates move towards each other (convergent)

Question 3

Define Conservative Plate Margin

Answer 3

2 plates slide past each other

Question 4

Define Magma Plume

Answer 4

Localised thermal currents in mantle that rise vertically (hot spot)

Question 5

Define Seismicity

Answer 5

Earthquakes

Question 6

Define Vulcanicity

Answer 6

Volcanic Activity

Question 7

Define Rift Valley

Answer 7

Formed at continents with constructive plate margin

Question 8

Define Subduction

Answer 8

When a denser plate slides under a lighter plate into the mantle

Question 9

What processes occur at Constructive Plate Margins

Answer 9

Oceanic - sea floor spreading at mid-ocean ridges (e.g: Mid-Atlantic Ridge)
Continental - stretching + collapse of crust = rift valleys (e.g: Great African Rift Valley)

Question 10

Outline how Mid-Ocean Ridges form

Answer 10

Submarine mountains have transform faults - 90 degrees from plate boundary = shallow earthquakes + ridge separation

Question 11

How do Mid-Ocean Ridges form volcanoes?

Answer 11

Middle of ridge magma rises to form new crust.
Volcanic eruption builds up submarine volcanoes - can grow to form volcanic island

Question 12

Outline how Rift Valleys are formed

Answer 12

Lithosphere stretches and fractures into parallel faults - land between = valleys - separated by land blocks (horsts)

Question 13

Outline the case study African Rift Valley

Answer 13

Eastern section moving NE & Western section moving W/NW
4000km length (Mozambique - Red Sea) & 600m high walls