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How deep is the earth's crust?

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Many rocks now making up Earth's crust formed less than 100 million (1 × 10 8) years ago; however, the oldest known mineral grains are about 4.4 billion (4.4 × 10 9) years old, indicating that Earth has had a solid crust for at least 4.4 billion years. read more

The crust of the Earth is of two distinctive types: Oceanic: 5 km (3 mi) to 10 km (6 mi) thick and composed primarily of denser, more mafic rocks, such as basalt, diabase, and gabbro. Continental: 30 km (20 mi) to 50 km (30 mi) thick and mostly composed of less dense, more felsic rocks, such as granite. read more

The earth's crust is between three to five miles deep under the oceans (oceanic crust) and about 25 miles deep under the continents (continental crust). This is very thin in comparison to the other layers of the planet. read more

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