Rocks

 IGNEOUS ROCKS  The word "igneous" comes from a Greek word for fire. Deep inside the earth, the temperature is very high and the [|minerals] there are in liquid form called magma. As the magma pushes towards the earth's surface, it starts to cool and turns into solid igneous rock.
 * [[image:boy2.gif]] * 70% of all the rocks on earth are sedimentary rocks.
 * The oldest known rock lies in Canada. The Acasta gneiss, a metamorphic rock, is 3.96 billion years old. **

 SEDIMENTARY ROCKS

The earth's surface is constantly being eroded. Long time ago, the pieces become pressed together and form solid rock called 'SEDIMENTARY ROCKS'. SEDIMENTS can harden into sedimentary rock in 2 ways. They are : -pressure & -cementing

Rressure is as layer after layer of sediments are deposited, the lower layers are pressed together tightly under the weight of the layers above.

Cementing is some sediments are glued together by minerals dissolved in water.

METAMORPHIC ROCKS Metamorphic rocks form deep in the earth where high temperature, great pressure, and chemical reactions cause one type of rock to change into another type of rock. Metamorphic rocks begin to form at 12-16 kilometers beneath the earth's surface.