The outer shell of Earth that extends to a depth of 100km is called the lithosphere.

Here's why:

* Lithosphere: This layer is composed of the Earth's crust and the uppermost part of the mantle. It's relatively rigid and brittle. The lithosphere is broken into tectonic plates, which move and interact, causing earthquakes, volcanoes, and mountain building.

Let me know if you'd like to know more about the Earth's structure!