Plate tectonics

Question 1

What are the four layers of the earth?

Answer 1

1. The crust
2. The mantle
3. The outer core
4. The inner core

Question 2

What does the crust include?

Answer 2

Part of the litheosphere which is also made up by the uppermost part of the mantle

Question 3

What are the two types of crust?

Answer 3

1. Continetal crust: thicker (70km) but less dense and is made up of graphite ( it is also older 1500m+)
2. Oceanic: thinner ( 5-10km) But denser composed on bansalt younger (200m yrs)

Question 4

Give three facts about the mantle

Answer 4

1. thickest layer
2. 2900km deep
3. made up of molten and semi-molten

Question 5

What is the asethonsphere?

Answer 5

the fluid, upper part of the mantle which the lithosphere sits on

Question 6

What is paleomagntism?

Answer 6

the record of the earths magnetic field preserved in magnetic minerals

Question 7

Who discovered the Pangea theory

continetal drift

Answer 7

Alfred Wegener

Question 8

What is pangea?

Answer 8

A supercontinent that was around 200 million years ago ( current continents all together)

Question 9

Give three pieces of evidence that supports the continetal drift theory?

Answer 9

1. jigsaw fits between continents e.g. south america and west africa
2. similar rock squences in north scotland and east canada
3. similar fossils in india to ones australia

Question 10

What is lithnosphere?

Answer 10

the combination of crust and upper mantle

Question 11

What is a plume?

Answer 11

a hot column of magma that arises from deep in the earth

Question 12

What is a fault line?

Answer 12

A crack in earth caused by tectonic movement

Question 13

what is a rift valley?

Answer 13

a long deep valley found at a fault line

Question 14

What is sea floor spreading?

Answer 14

The theory that the ocean floor is moving away from the Mid ocean ridge

Question 15

What is a Mid ocean ridge?

Answer 15

An underwater mountain range where the crust is actively spreading

Question 16

What does the plate tectonic theory state?

Answer 16

That the earth is made up of 7 rigid plates which are moving

Question 17

What does the plate tectonic theory suggest about the lithosphere and the asthenosphere?

Answer 17

That the lithosphere can slide over the asthnosphere to create plate movements

Question 18

What occurs to counteract sea floor spreading?

Answer 18

subduction in ocean trenche to destory crust

Question 19

What is ridge push?

Answer 19

At constructive plate boundaries, oceanic ridge creates a denser lithosphere, causing it to slide on the sloped asthenopshere by the force of gravity.

ridge push is less important then slab pull in causing movement of plate

Question 20

What is slab pull?

Answer 20

A subduction zone is formed when to plates move towards eachother. The denser oceanic plate subducts under the less dense plate. As the plate sinks, gravity pulls the plate down into the mantle.

At a destructive plate boundary

Question 21

What are convection currents?

Answer 21

Heat driven cycles which support the movement of the lithosphere plate

this plus slab pull and ridge push help cause tectonic plate movement

Question 22

What are ocean trenches?

Answer 22

Subduction of oceanic plate causing a trench

Question 23

How do island arcs form?

Answer 23

1) Two oceanic plates converge at a destructive plate boundary.
2) The denser oceanic plate subducts beneath the other less dense oceanic plate.
3) This allows magma to rise through the cracks and volacnic eruptions occur on the seabed.
4) Over time, repeated volcanic eruptions built more volcanoes above the sea level, forming a curved chain of islands.

eventually causing a curved chain

Question 23

What is an hot spot?

Answer 23

an area of crust heated by the magma plume away from a plate boundary