Paper 1- Plate tectonic theory

Question 1

mantle definition

Answer 1

The mantle is a layer inside a terrestrial planet

ranges from 500 to 4000 degrees

Question 2

lithosphere definition

Answer 2

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

Question 3

characteristics of continental crusts

Answer 3

Relatively old

Thick

covers 29% of Earths surface

Question 4

characteristics of oceanic crust

Answer 4

thin

younger

Question 5

why does the global distribution of earthquakes provide key evidence for the theory of plate tectonics

Answer 5

the distribution is not random

Earthquake activity is concentrated into belts where there is more stress on the crust

fewer earthquakes away from the belts indicates more stable regions of crust.

Question 6

names of seven major tectonic plates of the world

Answer 6

African plate

Antartic plate

Pacific plate

North American

Eurasian

Indian Austrailian plate

South American

Question 7

What was Pangea?

Answer 7

Supercontinent approximately 200 million years ago

Question 8

Types of plate margins

Answer 8

Constructive

Destructive

Conservative

Question 9

What happens at a constructive plate margins

Answer 9

crust is moving apart and a new crust is forming

this occurs at spreading ridges on the sea floor or along rifts if along land

Question 10

Learn labelled diagram of constructive, destructive + conservative margins

Answer 10

poo

Question 11

constructive boundary occurance description

Answer 11

the mantle plume injects magma into the faults

this feeds the volcanoes and forms new rock inside the faults thereby pushing the ridge apart

Crust also moves apart because of slab pull

Question 12

characteristics of volcanoes at constructive plate margins

Answer 12

Produce hot, runny lava

Often of the fissure type

Typically “free flowing”

Gentle slopes

Question 13

Why has iceland formed?

Answer 13

Area of high volcanic activity along mid-Atlantic ridge

Volcanos builts up above sea level

Lava flows have merged and solidified to form extensive areas of land

Question 14

What happens in the subduction zone?

Answer 14

Ocean crust is taken down towards the asthenosphere and heated

this provides a source of magma that is pressurised upwards to the surface forming rhyolite-type volcanoes

Earthquakes are generated as ocean crust slides beneath ocean crust

Question 15

What are volcanic “island arcs”?

Answer 15

Arcuate chains of volcanic islands found along subduction zones

They make an arc shape because the earth is a sphere

The west indies in the Carribean

Examples in the Pacific

Question 16

What are the main characteristics of ocean to continent destructive margins?

Answer 16

ocean crust always descends beneath

Andesitic volcanoes form above the subduction zone

the compression also folds and fractures the continental crust, forming fold mountains

Question 17

examples of composite volcanoes along desrtuctive margins

Answer 17

Volcanoes in the Andes

Volcanoes in the cascade range USE e.g St Helens

Question 18

What are the characteristics of continent to continent collision margins?

Answer 18

No subduction and no active volcanoes

Both sections of continental crust are folded, fractured

compression along the boundary uplifts rocks fold mountains

Earthquakes result from compression, fracture and uplift of rock

Question 19

Characteristics of conservative plate margins

Answer 19

Plates neither push nor pull apart

shear stresses are produced

Question 20

Why are there no volcanoes at conservative plate boundaries?

Answer 20

There is no rising mantle plume and no subduction

therefore there is no source of magma

Question 21

Give information about the San Andreas fault

Answer 21

over 800 miles long

The Pacific plate side is moving north-west more rapidly than the North American plate creating sheer stress

came into existence 15 to 20 million years ago

Question 22

Earthquake key points

Answer 22

Earthquakes dont only happen at plate margins

Earthquakes happen wherever rock is under stress, and plate tectonics creates stresses in the interior of plates as well as along the margins

Question 23

Longest rift system in the world

Answer 23

San Andreas fault

Question 24

Example of a hotspot

Answer 24

Hawaii active for 70 million years

Question 25

What is a hot spot

Answer 25

Area of crust overlying a rising mantle plume

this provides a source of magma causing volcanism

Can occur far from plate boundaries beneath both ocean and continental crust

the hot spot is stationary and the crust moves across it