Destructive Landforms Flashcards
1
Q
What are the types of convergence?
A
- Oceanic to Continental
- Oceanic to Oceanic
- Continental to continental
2
Q
Why does subduction occur?
A
When plates collide the denser plate is taken down into the mantel. This creates several features.
3
Q
Earthquakes are triggered because?
A
There is an increase in heat and friction which builds up to create shallow- to deep-focus earthquakes.
4
Q
What three features are found at destructive margins?
A
- Deep ocean trenches
- Island arcs
- Volcanoes
5
Q
The characteristics of deep ocean trenches are?
A
- Asymmetrical and narrow.
- Mark where the plate begins to descend.
- Can be up to 10 km deep.
6
Q
At oceanic - continental margins…
A
- Young fold mountains are formed as rocks are scrapped off and folds the continental plate. e.g. the Andes
- Deep ocean trenches form along the seaward edge e.g. the Peru- Chile trench.
- Conical shaped volcanoes form as silica-rich magmas erupt on the surface.
7
Q
At oceanic- oceanic margins..
A
- a denser or faster oceanic plate gets subducted beneath another oceanic plate.
- similar process to oceanic/continental margins.
- Island arcs form, for example Marianas Islands, Aleutian Islands.
- Shallow - to deep - focus earthquakes occur.
8
Q
Island arcs form when..
A
- heat and friction melt the subducted plate to create plumes of magma that rise up.
- molten magma erupts on ocean floor and grows in size over millions of years to reach water surface.
- can form large land masses such as Japan.
9
Q
At continental - continental convergence…
A
- continents have similar density, so don’t get subducted.
- sediments from the ocean floor and some volcanic rocks are pushed up to form young fold mountains.
- Mountain chains have deep roots in the lithosphere.
- For example the sea-floor spreading of Indo-Australian plate in NE direction collided with the Eurasian plate to form the Himalayas.
