The oceanic crust is best described as which of the following?

• A. It is thin and dense and lies beneath the oceans
• B. It is thick and less dense
• C. It is part of the mantle
• D. It is the same as continental crust

Answer: (A)

Oceanic crust forms the floor of the oceans and is made mainly of basalt, which makes it relatively dense compared with continental crust. It is also thin, averaging about 5–10 kilometers in thickness, which is much less than continental crust. This combination of being thin and dense means it sits low on the mantle and can be subducted beneath other crust at tectonic boundaries. It’s part of the lithosphere, not the mantle itself, and it differs in composition and thickness from continental crust. So describing it as thin and dense and lying beneath the oceans best captures its key characteristics.