Plate Movement and convergent plate boundaries Flashcards
How many layers make up the structure of the Earth
Inner core - solid
Outer core - liquid
Mantle - molten rock
Crust - solid rock
Outline some AO1 knowledge about oceanic crust.
Oceanic:
Dense
subduction can occur (can be destroyed) younger (because it can be renewed)
BASALT
Faster moving.
What are the names of the sections that make up the Crust/ mantle (as these two layers are not completely separate)
Lithosphere - crust + little bit of mantle (80-90 km thick)
Asthenosphere - very viscous.
Mesosphere - section below Asthenosphere in the mantle. Viscous.
Give some AO1 knowledge about continental crust:
Thicker
Less dense
CAN’T be subducted
CAN’T be renewed/destroyed
GRANITE / SEDIMENTARY
Slow moving.
What 3 ways do plates move?
Convection currents.
(Friction between lithosphere and asthenosphere pulls tectonic plates)
Ridge push AKA Gravitational sliding.
Slab pull.
They all work together.
Explain ridge push / gravitational sliding?
Driving force for plate movement,
Occurs at mid-oceanic ridges
rigid lithosphere sliding down hot, raised asthenosphere underneath mid-ocean ridges - push is caused by gravity.
Gravitational force occurs because ridge = higher elevation than the rest of the ocean floor.
What is slab pull?
Plate cools as it moves away from mid ocean ridge (cool and dense so subducts).
Pulls rest of slab into mantle below like a conveyor belt.
What is the benioff zone?
The area where the subducting plate and the squished upper plate meet. There is LOTS OF FRICTION here.
What is a convergent plate boundary
Two plates moving towards each other. One subducts beneath the other.
Why do volcanoes occur at subduction zones?
Give an example
compression of continental crust (fold mountains, some of which will be volcanoes.)
melting plate underneath creates volcanoes.
This forms a volcanic arc.
The ANDES
What are the andes a good example of?
A volcanic arc.
occurring at an oceanic and continental convergent plate boundary.
the andes include volcanoes like Nevada Del Ruiz and have the Nazca oceanic plate and the South American continental plate.
What is the difference between an oceanic : continental convergent plate boundary and a Oceanic : Oceanic convergent plate boundary?
Get and island arc chain (e.g Mt Peleé) instead of a volcanic arc.
E.G - the Caribbean (Mt. Peleé)
Continental : continental collision boundaries.
Example:
What happens at convergent plate boundaries in this situation?
Himalayas
no volcanoes because no subduction.
Occur when oceanic lithosphere has fully subducted so ocean disappears and continental plates meet.
Accretionary wedge (ocean floor sediments compress into fold mountains) have bridged the gap between the plates creating the Himalayas.
