When the molten earth cooled the landscape may have looked a bit like this picture. The surface would have been rough and uneven, with eruptions of lava. Rocks would be moving, floating on the thick mineral soup beneath them. The rocks would crack and break, colliding with each other as they cooled.

     Before there was life on earth, there were rocks and minerals. The crust of the earth is made up of them. Today we see rocks and stones and great rocky mountains when we look at the earth . These are pieces of non-living, inorganic matter.  However, there are new kinds of rocks in the world now, rocks that have come about because of geological processes. These processes break rocks apart and then cement the tiny pieces of sand and silt together again to make different kinds of rocks.

Geologists have divided rocks into three groups:

Igneous Rocks: formed by the cooling of molten material

• Introduction to Igneous Rocks
• Volcanic Eruptions
• Lava is a liquid

Sedimentary Rocks: formed from tiny particles that are cemented together

• Introduction to Sedimentary Rocks
• How are Sedimentary Rocks Formed

Metamorphic Rocks: formed from sedimentary rocks by heat and pressure

• Introduction to Metamorphic Rocks

Click on the rock types to learn more about them.