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crust





continental and oceanic crust
Image credit: US Geological Service
The solid surface layer of a planet or moon. Earth’s crust, which forms the upper part of the lithosphere, makes up about 0.6 percent of Earth's volume and 0.4 percent of its mass. It varies greatly in thickness. Under the oceans, the crust (mainly composed of basalt) ranges between 5 and 11 km (3 and 6.8 miles). Under the continents, the crust (made mostly of granite) ranges between 19 and 64 km (12 and 40 miles) thick. As in the case of other planetary bodies in the inner Solar System, it consists of lighter rocks that rose to the surface when molten, leaving denser materials to form the mantle and core. Large solid bodies in the outer Solar System typically have crusts made of water-ice.


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   • GEOLOGY AND PLANETARY SCIENCE