Kinds of Rocks

Earth has different kinds of rocks.

Some rock is made from lava.

Lava flows out of volcanoes and onto land.

The lava cools and becomes hard.

Lava rock becomes rock.

Lava that becomes rock is called igneous rock.

Water can move rocks around the earth.

Rivers can break off little pieces of rock from mountains.

These pieces of rock are called sediment.

The river moves the sediments across land.

When the river is slow, it drops the sediment.

Sand by a river is sediment.

Sediment adds on top of other sediment.

Very slowly, the sediment pushes together, and makes rock.

This kind of rock is called sedimentary rock.

Some rock is made inside of the Earth.

Rock inside of the Earth is very hot.It is under pressure.

Pressure means it is pushed very hard by the rock around it.

Heat and pressure change the rock.

This rock is called metamorphic rock.