Continents float on the mantle because continental rocks are less dense than the rock that makes up the mantle.

Here's why:

* Continental crust is primarily composed of granite, which is rich in lighter elements like silicon and oxygen.

* Mantle rock is mostly peridotite, which is denser due to its higher content of heavier elements like iron and magnesium.

This density difference is similar to how a piece of wood floats on water. The wood is less dense than the water, so it displaces enough water to support its weight and stay afloat.

Similarly, the less dense continental crust "floats" on the denser mantle, forming the landmasses we see.