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Continental Drift

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The gradual movement of Earth's continents across the ocean floor over geological time.

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Plate Tectonics

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The theory that Earth's outer shell is made up of large pieces (plates) that move and interact with each other.

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Pangaea

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A supercontinent that existed about 300 million years ago, when all the Earth's continents were joined together as one landmass.

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Crust

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The outermost layer of the Earth, made up of solid rock.

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Mantle

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The thick layer of the Earth below the crust, made of hot, semi-solid rock.

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Tectonic Plates

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Large pieces of Earth's lithosphere (the crust and upper mantle) that move and interact with each other.

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Fossil

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The remains or traces of ancient plants and animals preserved in rock.

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Sea-Floor Spreading

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The process by which new oceanic crust forms at mid-ocean ridges and pushes the older crust away.

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Mid-Ocean Ridge

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An underwater mountain range where tectonic plates are pulling apart and new crust is being formed.

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Subduction

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The process where one tectonic plate slides under another, usually causing earthquakes or volcanic activity.