Collision Margin

Question 1

Sub plate processes

Answer 1

-Initially, as two continents approached one another, the oceanic lithosphere between them subducts below one of the continents.

-Over time, the oceanic lithosphere becomes detached from the above continents, it slowly melts and becomes assimilated fully into the asthenosphere. Eventually all subduction stops below a collision margin.

Question 2

Plate processes

Answer 2

-As the two continental plates converge, sediments are laid down on the sea floor.
-(as oceanic lithosphere subducts- sediment that has been deposited on top of it is scraped off and builds up on the surface when the continents collide.)
-sediment is also deposited on the sea bed by rivers flowing off the edge of continents.
-two continental plates converge - no subduction of plate material as continental rocks are both light and resist downward motion.

Question 3

Fold mountains

Answer 3

-edges of the crusts buckle and any sediments deposited between the two continents are compressed into folds and crushed upwards into Fold Mountains.
-process of deformation causes faults in the mountains. (deposited sediment is from the past when approaching continents were separated by ocean).
-where fold mountains form the Earth’s crust is at its thickest. The sediments continue to rise as a series of huge ridges.

Question 4

Seismic activity

Answer 4

-area of collision is riddled with fault lines giving rise to earthquakes.
-no subduction = no deep foci earthquakes.
-When plates are converging, there is increased friction between them
-plates may become locked for a period of time, pressure builds and eventually the pressure is released in a sudden movement along a fault as seismic waves (an earthquake).