What is the ocean floor made of, and why are some clouds flat on top?

We explore the curious questions that science can answer

The oceanic crust is about four miles thick (Getty/iStock)

What is the ocean floor made of, and how thick is it?

The crust beneath the ocean differs from the crust beneath land in several ways: it is thinner, denser, younger and made in different ways. Both have rocks made up of the same minerals, just in slightly different proportions. The crust contains silicon, aluminium, iron, magnesium, calcium, sodium and potassium oxides – just like any other rock. However, the oceanic crust is only about four miles thick.

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