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Earthquakes and Volcanoes (Plate Boundaries (Destructive ( image, Two…
Earthquakes and Volcanoes
Types of crust
Oceanic
Usually carries ocean
Thinner (5-10km thick)
More Dense
Sub-ducted
Newer
Made up of Gabbro and Basalt
Continental
Usually caries land
Thicker (30-50km thick)
Less Dense
Cannot be sub-ducted
Older - Cannot be created or destroyed
Made up of mainly granite
Plate Boundaries
Destructive
Two plates
move towards each other
and
collide
.
The oceanic plate
subducts
under the continental plate because it is more dense.
The oceanic crust melts in the
subduction zone/mantle
.
Magma is formed and then rises because it's less dense and due to high pressure. The magma forces its way through the crust and forms a composite cone volcano on the surface.
The continental plate gets stuck on the oceanic plate and then buckles and crumples to form fold mountains
Earthquakes can form here due to the oceanic plate rubbing against the continental plate as it subducts. This build up pressure and friction and when released can cause an earthquake.
Constructive
Conservative
Two plates move
past each other
(opposite, or same direction.
The plates get stuck, and
locked
in place.
This builds up
pressure
and
friction
within the plate.
This
pressure
then gets too much and suddenly released, the plates '
jolt
' and
slip past each other
releasing the
pressure
as shockwaves from the
focus
(point at which the pressure is released).
These shock waves cause the plates to
move
/vibrate causing an earthquake.
No volcanoes = no magma, no subduction or rising magma.
