The asthenosphere doesn't have a fixed thickness, as it's not a distinct layer with a clear boundary. Instead, it's a zone within the upper mantle that's characterized by partial melting and ductility, making it weaker and more fluid than the surrounding rock.

Here's a breakdown:

* Depth: It's typically considered to be around 100-200 km deep, though it can extend deeper in some areas.

* Variation: The asthenosphere's thickness can vary based on location, tectonic activity, and other geological factors.

* No defined boundary: The transition between the lithosphere (the rigid outer layer of Earth) and the asthenosphere is gradual.

So, while we can provide a general range for its depth, it's more accurate to think of the asthenosphere as a zone with varying thickness rather than a solid layer with a specific depth.