Earth's Crust
The crust covers the mantle and we live on it. The thinnest part of the crust is in under the ocean and is called oceanic crust. The thickest crust is called a continental crust and is thinner than the oceanic crust because it is made up with Granites. Many rocks are now making the Earth's crust less and less than 100 million years ago; but the oldest mineral grains are 4.4 billion years old, that means that the Earth has had a solid crust for at least 4.4 years!!!
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