The distinction between the crust and mantle is primarily based on a difference in composition.

Here's a breakdown:

* Crust: The outermost layer of Earth, relatively thin and composed primarily of lighter elements like silicon, oxygen, aluminum, and sodium. It can be further divided into oceanic crust (denser, mostly basalt) and continental crust (less dense, mostly granite).

* Mantle: The thick layer beneath the crust, composed mostly of denser elements like magnesium, iron, and calcium. The mantle is predominantly made of silicate minerals.

While temperature and pressure also increase with depth and contribute to the difference, the primary distinction is the chemical composition.