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Rocks

Rocks make up the earth’s crust and are the most basic unit of geology. Geology is the study of the earth and the way it is made. Each rock tells a story of how and where it was made. They provide clues to the history of our planet, record changes in the environment that happened millions of years ago, and contain fossils that supply evidence of life forms over the last 3.5 billion years. Geologists (people who study geology) define a rock as a combination of minerals. Some rocks do not have minerals but are made up of glasses (obsidian) or organic (coal) material.

Rocks

Rocks