The lithosphere floats on a layer of the Earth's mantle called the asthenosphere.

Here's why:

* Lithosphere: This is the rigid, outermost layer of Earth, composed of the crust and the uppermost part of the mantle.

* Asthenosphere: This is a semi-solid layer of the upper mantle located beneath the lithosphere. It's characterized by its ability to deform and flow over long periods due to high temperatures and pressures.

The asthenosphere acts like a viscous fluid, allowing the lithospheric plates to move and interact, driving processes like plate tectonics.