![]() The primordial crust was very thin and was probably recycled by much more vigorous plate tectonics and destroyed by significant asteroid impacts, which were much more common in the early stages of the solar system. Partly by analogy to what is known about the Moon, Earth is considered to have differentiated from an aggregate of planetesimals into its core, mantle and crust within about 100 million years of the formation of the planet, 4.6 billion years ago. ![]() Some of these less dense rocks, such as granite, are common in the continental crust but rare to absent in the oceanic crust. The continental crust is typically from 30 km (20 mi) to 50 km (30 mi) thick and is mostly composed of slightly less dense rocks than those of the oceanic crust. The oceanic crust is 5 km (3 mi) to 10 km (6 mi) thick2 and is composed primarily of basalt, diabase, and gabbro. The crust occupies less than 1% of Earth's volume.1 The oceanic crust of the sheet is different from its continental crust.
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