Many rocks have traveled a long way to be here, from places
like California, Scotland, Mexico, and even another part of the solar system! Some formed about 4.5 billion years ago—that makes them as old as the
Earth. Others are only 900 years old—that's just a baby in rock years.
Every rock has a story to tell. And every story gives us clues about the history of the Earth.
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Igneous rocks formed from melted rock deep inside the Earth. |
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Sedimentary rocks formed from layers of sand, silt, dead plants, and animal skeletons. |
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Metamorphic rocks formed from other rocks that are changed by heat and pressure underground. |
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