2A: Plate tectonic theory, distribution of earthquakes + volcanoes, and the physical processes causing them

Question 1

Mantle

Answer 1

deformable: ductile not molten

500 to 4000 degrees

Question 2

lithosphere

Answer 2

The part that moves

rigid outer part of the earth, consisting of the crust and upper mantle.

Question 3

Characteristics of continental crust:

Answer 3

Relatively old

Thick

Covers 29% of the earths surface

Question 4

Characteristics of oceanic crust:

Answer 4

Thin

younger

Question 5

When was plate tectonic theory discovered?

Answer 5

1960’s

Question 6

Why does global distribution of earthquakes provide evidence for plate tectonic theory?

Answer 6

Distribution is not random

Earthquake activity concentrated into belts where ther is more stress

Fewer earthquakes away from these belts

Indicating stable regions

Question 7

Names of Seven major tectonic plates

Answer 7

African plate

Antartic plate

Pacific

North American

South American

Eurasian

Indian-Australian plate

Question 8

Why does plate motion occur?

Answer 8

Convection currents in the mantle

Question 9

What rate do the plates move

Answer 9

1-10 cm per year

Question 10

What was “Pangea”

Answer 10

Super continent aprox. 200 million years ago

Question 11

3 types of plate margins

Answer 11

Constructive

Destructive

Conservative

Question 12

Constructive plate margin:

Answer 12

Crust moves apart

New crust forms

Occurs at spreading ridges

Question 13

Characteristics of constructive plate margins

Answer 13

Hot, runny lava

Often fissure type

Typically free flowing

Gentle slopes

Question 14

Why has Iceland formed

Answer 14

Area of high volcanic activity along mid-Atlantic ridge

Volcanoes built up above sea level

Question 15

Volcanic island arcs:

Answer 15

Chains of volcanic islands found along subduction zones

Arc shape because earth is a sphere

E.g. West Indies

Question 16

Characteristics of ocean to continent destructive margins:

Answer 16

Ocean crust always descends beneath

“Andesitic” volcanoes form above subduction zone

Fold mountains

E.g Andes / St Helens

Question 17

Characteristics of continent to continent collision margins:

Answer 17

No subduction zones + active volcanoes

Fold mountains

Fractured, uplifted rock

Question 18

Characteristics of conservative plate margins:

Answer 18

Plates neither push together nor pull apart

Shear stress is produced

Question 19

Longest rift system in the world?

Answer 19

San Andreas fault

Question 20

What is a hotspot?

Answer 20

Area of crust overlying a mantle plume. Source of Magma

Can occur from plate boundaries beneath both ocean and continental crust

Hot spot is stationary

The crust moves accross it