What term describes the solid, brittle outermost layer of the Earth?

The term that describes the solid, brittle outermost layer of the Earth is the lithosphere. This layer encompasses both the Earth's crust and the uppermost portion of the mantle. The lithosphere is characterized by its rigidity and is where geological processes such as tectonic activity, earthquakes, and volcanic eruptions occur.

The lithosphere plays a critical role in the Earth's geological structure as it interacts with the underlying asthenosphere, which is semi-solid and allows for the movement of tectonic plates. This movement is essential for the formation of mountains, earthquakes, and other geological phenomena.

In contrast, the hydrosphere refers to all the water on Earth (liquid, vapor, and ice), while the atmosphere consists of the layers of gases surrounding the planet. The stratosphere is a particular layer within the atmosphere that contains the ozone layer and is not related to the Earth's solid structure. Understanding these terms helps clarify the distinct layers and components of our planet.