1. The Earth’s Crust

2. Plates
The earth’s crust is broken into several large slabs of rock called plates
Each plate floats on a partially melted layer in the upper mantle
The plates carry the earth’s oceans and continents

4. Movement Over time the plates move
Millions of years ago the continents were joined in one supercontinent called Pangea
Over millions of years the plates have drifted to where they are currently
Continental drift – the theory that the continents were once joined and then slowly drifted apart
The movement of plates is very small and cannot be felt, only about 4 inches a year

6. Movement
As the plates move they are bound to crash into each other, pull apart, grind together, or slide past each other
Plate tectonics – the activities of continental drift that create many of the earth’s physical features
The shifting of plates means that the earth could look very different millions of years from now

7. Colliding and Spreading Plates
Mountains are formed when two plates collide
Subduction – occurs when a heavier sea plate dives beneath the lighter continental plate
When the sea plate plunges down it becomes molten material and eventually bursts out as magma forming volcanic mountains

8. Colliding and Spreading Plates
Spreading – when sea plates pull apart. The resulting rift allows magma to come up and harden to build underwater mountains or volcanoes
Fault – when two plates grind or slide past each other creating a crack in the earth’s crust