Science glossary film: Crust

The surface layer of a rocky planet or other astronomical body, usually chemically distinct from the mantle beneath it. Like other planets in the inner Solar System, the Earth's crust formed when molten rock cooled early in the planet's history. It is up to 70 kilometers thick, and composed mostly of granite in the continental crust, and basalt in the oceanic crust.

Like other planets in the inner Solar System, the Earth's crust formed when molten rock cooled early in the planet's history. It is up to 70 kilometers thick, and composed mostly of granite in the continental crust, and basalt in the oceanic crust.