Destructive Landforms

Question 1

What are the types of convergence?

Answer 1

1. Oceanic to Continental
2. Oceanic to Oceanic
3. Continental to continental

Question 2

Why does subduction occur?

Answer 2

When plates collide the denser plate is taken down into the mantel. This creates several features.

Question 3

Earthquakes are triggered because?

Answer 3

There is an increase in heat and friction which builds up to create shallow- to deep-focus earthquakes.

Question 4

What three features are found at destructive margins?

Answer 4

1. Deep ocean trenches
2. Island arcs
3. Volcanoes

Question 5

The characteristics of deep ocean trenches are?

Answer 5

1. Asymmetrical and narrow.
2. Mark where the plate begins to descend.
3. Can be up to 10 km deep.

Question 6

At oceanic - continental margins…

Answer 6

1. Young fold mountains are formed as rocks are scrapped off and folds the continental plate. e.g. the Andes
2. Deep ocean trenches form along the seaward edge e.g. the Peru- Chile trench.
3. Conical shaped volcanoes form as silica-rich magmas erupt on the surface.

Question 7

At oceanic- oceanic margins..

Answer 7

1. a denser or faster oceanic plate gets subducted beneath another oceanic plate.
2. similar process to oceanic/continental margins.
3. Island arcs form, for example Marianas Islands, Aleutian Islands.
4. Shallow - to deep - focus earthquakes occur.

Question 8

Island arcs form when..

Answer 8

1. heat and friction melt the subducted plate to create plumes of magma that rise up.
2. molten magma erupts on ocean floor and grows in size over millions of years to reach water surface.
3. can form large land masses such as Japan.

Question 9

At continental - continental convergence…

Answer 9

1. continents have similar density, so don’t get subducted.
2. sediments from the ocean floor and some volcanic rocks are pushed up to form young fold mountains.
3. Mountain chains have deep roots in the lithosphere.
4. For example the sea-floor spreading of Indo-Australian plate in NE direction collided with the Eurasian plate to form the Himalayas.