If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.

PLATE TECTONICS

So how do convection currents cause plate movements?

As 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.

The Earth’s crust is divided into 8 major plates which are moved in

various directions.

WHAT ARE TECTONIC PLATES MADE OF?• Plates are made

of rigid lithosphere.The lithosphere is made up of the crust and the upper part of the mantle.

CONTINENTAL DRIFT

Alfred Wegener 1900’scontinents were once a single land mass that drifted apart atop a liquid core.

EVIDENCE OF PANGEA

WHAT WAS THE PROBLEM

WITH CONTINENTAL

DRIFT THEORY?

SEA FLOOR SPREADING

SEA FLOOR SPREADING• Mid Ocean Ridges – underwater mountain

chains that run through the Earth’s Basins• Magma rises to the surface and solidifies and

new crust forms• Older Crust is pushed

farther away from the ridge

OCEANIC CRUST IS

MORE DENSE THAN

CONTINENTAL CRUST

LITHOSPHERE IS BROKEN INTO TECTONIC

PLATES

But why do tectonic

plates move?