The asthenosphere is a layer within the Earth's upper mantle, located below the lithosphere. It's characterized by its partial melting, which gives it a semi-solid, "plastic" consistency.

Here are some key features of the asthenosphere:

* Partially Molten: While not completely liquid, the asthenosphere contains pockets of molten rock. This molten material allows for slow, ductile flow.

* Ductile Flow: The pressure and temperature conditions within the asthenosphere enable rocks to deform under stress, like a very slow-moving fluid.

* Important for Plate Tectonics: The asthenosphere is the layer upon which the tectonic plates of the Earth's lithosphere "float" and move.

Let me know if you'd like more details on any of these features!