Tectonic Plates Flashcards
What has the plate tectonic theory shown
Plate tectonic theory has shown that the earth crust is not a solid mass but is split into smaller crystal plates which ‘float’ on the semi-molten upper mantle
What is the theory of plate tectonics
The movement of the plates, and the activity inside the Earth, is called the theory of plate tectonics.
State the processes in which plates move
Convection currents
Slab Pull
Ridge Push
What is a convection current
A convection current is the movement within the Earth’s mantle caused by the heat of the core.
Explain how convection currents cause plates to move
As the semi-molten rock in the mantle is heated it becomes less dense than its surroundings and rises. As it reaches the crust above, it spreads out carrying the plates above with it. As the semi-molten rock then cools, it gradually sinks back down to be re-heated
Explain how ridge push cause plates to move
At constructive boundaries, ocean ridges form high above the ocean floor.
Beneath ocean ridges the mantle melts; the molten magma rises as the plates move apart and cools down to form new plate material.
As the lithosphere cools, it becomes denser and starts to slide down, away from the ridge, which causes plates to move away from one another. This is called ridge push.
Explain how slab pull cause plates to move
At destructive boundaries, the denser plate sinks back into the mantle under the influence of gravity, which pulls the rest of the plate along behind it. This is called slab pull.
What is slab pull
Slab pull occurs when older, denser tectonic plate sink into the mantle, pulling newer and less dense sections of plate along behind
When does ridge push only happen
Ridge push occurs at constructive plate boundaries
When does slab pull only occur
Slab Pull occurs at only destructive plate boundaries
When do convection currents occur
Convection currents occur at constructive, destructive and conservative plate boundaries (it is the way plate move more generally)
Name types of plate tectonics
Types of tectonic plate
Destructive plate boundary
Constructive plate boundary
Conservative Plate boundary
Collision plate boundary (type of destructive)
Which plate boundaries move the quickest
Destructive plate margins move quicker than constructive and conservative plate margins
What happens at destructive plate boundaries
A destructive plate boundary is when oceanic crust moves towards continental crust. As the oceanic crust is denser (heavier), it is subducted (forced downwards).
Give an example of destructive plate boundaries
An example of destructive plate boundary: example the Nazca Plate moving towards the South American Plate.