Plate Tectonics

Question 0

Continental crust: (4)

Answer 0

Less dense than oceanic.
Variety of rock types.
20 - 80 km thick.
Richer in silica than oceanic.

Question 1

Oceanic crust: (4)

Answer 1

Approx 7 km thick.
Basaltic.
Mafic chemical composition.
More dense than continental.

Question 2

Mountain ranges form from:

Answer 2

Continental-continental collision. The continual convergence of the plates leads to further crumpling and mountain growth.

Question 3

Island arc:

Answer 3

A chain of volcanoes on the overriding plate at a subduction zone of oceanic lith.

Question 4

Continental splitting / rifting:

Answer 4

Occurs at divergent plate boundaries, forms new oceans between continents.

African Rift Valley - Dead Sea.

Question 5

Subsidence of lith below mountains, caused by the

Answer 5

Weight of the mountain range, forces the asthenosphere to flow from beneath the mountains. The lith and mountain range therefore subsides.

Question 6

Denudation:

Answer 6

From weathering and transportation of rock debris. Reduces the height of the mountains.

Question 7

Uplift occurs at

Answer 7

Cont-cont convergence of plates. Leads to the formation of mountains.

Question 8

Lithosphere: (3)

Answer 8

Earths outer shell.
Approx 100 km thick.
Thinner beneath the oceans, thicker beneath the continents.

Question 9

Asthenosphere: (4)

Answer 9

Solid, but behaves like a liquid because of high temp and pressure.
Heat generation drives convection.
Slow rate of flow.
Plate tectonics - weakness of ast allows lithospheric plates to slide around in motion.