World Builders™                                                                               Session Two  --  Geology      

How Rocks are Formed

Very hot rocks are liquid: it takes time for them to solidify and form a crust on a world.


    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

Sedimentary Rocks: formed from tiny particles that are cemented together

Metamorphic Rocks: formed from sedimentary rocks by heat and pressure

Click on the rock types to learn more about them.

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© 1996,1997, 1998, 1999, 2000, 2002, 2003.   Elizabeth Anne Viau. All rights reserved. This material may be used by individuals for instructional purposes but not sold. Please inform the author if you use it at .