Plate Tectonics

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Plates moving in any direction causes earthquakes

The worst are caused by plates rubbing past each other as in C

This happens along the Californian coast

Slide 13

Sea floor spreading

Large continents begin to crack and split apart

The gaps fill with water

Small seas become oceans

The mid ocean ridge continues to produce new crust

Slide 14

Why spread?

Why is the Atlantic still getting wider

The plates are pulled apart by convection currents in the mantle below

Caused by heat released from natural radioactive processes

At the mid Atlantic ridge molten rock from below rises up to fill the gap with new basaltic rock

Slide 15

More evidence

More evidence has been found for Wegeners theory

The Earths North and South pole have flipped many times

These leaves magnetic ‘stripes’ in rock containing iron minerals

Slide 16

So the Earth must be growing?

Dense heavy oceanic crust can be subducted below less denser continental crust.

The friction melts rock

This magma rises through the crust to form new volcanoes

This is happening in South America (The Andes)

Slide 17

Continents Collide

Eventually when plates move together the continental crust collides

The heat and pressure make metamorphic rock

It also pushes and folds the rocks into high mountains

The Himalayas rise to 8848m and are still growing today