Here's why:
* The Asthenosphere: This layer is located beneath the lithosphere (which includes the crust and the uppermost part of the mantle). It's characterized by being partially molten and having a relatively low viscosity. This allows the rigid lithosphere to "float" on top of it and move around.
* Tectonic Plates: The Earth's lithosphere is broken into these large, moving plates. The asthenosphere's fluidity allows the plates to move, interact, and cause phenomena like earthquakes, volcanoes, and mountain formation.
Let me know if you'd like more detail about the asthenosphere or tectonic plate movement!
