Plate tectonic - 3.1.5.2

Question 1

Lithosphere

Answer 1

The rigid top layer of the mantle and crust. Makes up the Earth’s plates.

Question 2

Asthenosphere

Answer 2

Part of the upper mantle which is semi-molten and ductile. Occurs at depths of 80 to 200 km below surface.

Question 3

Continental crust

Answer 3

The upper layer of the earth that is permanent and hence very old. It is relatively light and cannot sink at a plate boundary.

Question 4

oceanic crust

Answer 4

The upper layer of the earth that is continually being renewed and recycled. It is dense and sinks at a plate boundary.

Question 5

Plate Tectonics

Answer 5

The theory that Earth’s crust is divided into several plates that are constantly moving over the overlying mantle.

Question 6

Continental Drift

Answer 6

An out-dated theory which proposed that the continents moved across the earth’s surface.

Question 7

Palaeomagnetism

Answer 7

The study of old rocks which have the earth’s magnetic field ingrained in them when they were formed. This provided the evidence for sea floor spreading.

Question 8

Gravitational sliding

Answer 8

A proposed mechanism for plate tectonics. The movement of the lithosphere in response to gravity.

Question 9

Ridge Push

Answer 9

Areas of high elevation (mid ocean ridges) put pressure on the plate downslope causing it to move.

Question 10

Slab Pull

Answer 10

Cold, dense plates sink into the mantle (subduction) causing it to pull the remaining lithosphere with it.

Question 11

Convection Current

Answer 11

A circular current in the mantle caused by the difference in temperatures from the bottom to the top. The currents cause the Earth’s plates above them to move by about 2 to 10 cm a year

Question 12

Destructive plate boundary (Subduction Zone)

Answer 12

Two plates (oceanic and continental plate) move towards each other and the oceanic crust subducts underneath the continental crust creating volcanoes, earthquakes and fold mountains.

Question 13

Constructive plate boundary

Answer 13

Two plates (normally oceanic crust) move away from each other allowing magma to raise in-between the gap created. This creates volcanoes and mountain ridges.

Question 14

Destructive plate boundary (Collision)

Answer 14

Two continental plates move towards each other and creating fold mountains and large earthquakes (but no volcanoes).

Question 15

Conservative plate boundary

Answer 15

Two plates slide past each other creating large earthquakes.

Question 16

Fold mountains

Answer 16

Mountains created when areas of the earth crust have been bent and forced up by tectonic plates.

Question 17

Rift Valleys

Answer 17

A wide valley created when a constructive plate boundary caused a continental plate to be pushed apart.

Question 18

Ocean Ridges

Answer 18

An underwater mountain range formed at a conservative plate boundary.

Question 19

Deep Sea Trenches

Answer 19

A narrow steep sided depression in the ocean where one tectonic plate is subducting under another.

Question 20

Island Arcs

Answer 20

A chain of volcanic islands created by the rising magma of a subducting plate (associated with oceanic trenches)

Question 21

Magma Plumes

Answer 21

An upwelling of abnormally hot magma from within the earth’s mantle which create hotspots.