Transcript Plate Tectonics

Plate Tectonics
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The earth’s crust is made up of tectonic
plates
Tectonic plates move or float on top of the
upper mantle.
However they do not float freely.
The plates are forced in specific directions by
the flow of magma beneath.
Plate Tectonics – cont’d
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Plates move with the flow of magma.
The magma closer to the core heats and then rises
towards the surface as its density decreases.
Once the rising magma reaches the lithosphere it
moves in opposite directions.
It cools, falls back towards the core and the cycle
repeats.
The magma forms convectional currents.
Plate Tectonics – Convection Currents
Forces on Plates
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Tensional Forces occur where two tectonic plates are
pulled apart. The tension is created as the plates move
away from each other. Also called diverging plates or
boundaries
Compressional Forces occur where two tectonic
plates push together. They compress against each
other. Also called converging plates or boundaries
Each of these are caused by convection currents of
magma beneath the earth’s crust
Where’s the TENSION?
A
B
C
Where’s the Subduction /
Compression?