There are three kinds of rocks; each is formed a different way.
Igneous rock forms from magma. Igneous means "from fire." Deep beneath the surface of the earth it is so hot that rocks melt. This melted rock is called magma. When magma reaches the surface of the earth through volcanoes or cracks in the earth's crust, it is called lava. When magma or lava cools, it forms igneous rocks.
Sedimentary rock forms from sediment. When rock is exposed to rain, wind, or ice, little pieces break off, sometimes as fine dust or sometimes as chunks. When these pieces collect together as a layer beneath the ocean, they form sediment. When sediment is compacted by pressure, it hardens into sedimentary rock.
Metamorphic rock forms from other rock. Metamorphic means "changed form." Rock can get pushed beneath the surface of the earth, where great pressure and heat change it. Metamorphic rock is squeezed so hard that it becomes distorted and even the minerals inside it can change.
Click on the player below to watch a video on how the different types of rocks are formed...
Now click on each of the red boxes below to learn more about each type of rock...
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