 Rocks are formed on Earth as igneous, sedimentary, or metamorphic rocks. Igneous rocks form when rocks are heated to the melting point which forms magma. Sedimentary rocks are formed from the cementing together of sediments, or from the compaction (squeezing together) of sediments, or from the recrystallization of new mineral grains which are larger than the original crystals. Metamorphic rocks form from heat and pressure changing the original or parent rock into a completely new rock. The parent rock can be either sedimentary, igneous, or even another metamorphic rock. The word "metamorphic" comes from Greek and means "To Change Form".
The diagram above shows you how the rocks on Earth have been changed continually over time from one rock type to another. This changing of rock types is called the "Rock Cycle".
Click on the "Next" button to learn about what causes rocks to change!
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