Here's why:

* Location: The asthenosphere is a layer within the Earth's upper mantle, located below the lithosphere.

* Characteristics: It's a zone of semi-molten, partially solid rock that behaves like a viscous fluid over long periods. This property is key to plate tectonics.

* Role in Plate Tectonics: The asthenosphere's movement is crucial for the movement of the Earth's tectonic plates, which in turn drive earthquakes, volcanic activity, and mountain building.

So, while you can't see it or touch it directly, the asthenosphere is a fundamental part of the Earth's structure and plays a crucial role in shaping our planet.