What is the lithosphere primarily composed of?

The lithosphere is primarily composed of the Earth's crust and the uppermost part of the mantle. It encompasses the rigid outer layer of the Earth, which is where tectonic plates are found. This layer is solid, brittle, and is critical for understanding geological processes such as plate tectonics, earthquakes, and volcanic activity.

The crust consists of the various types of rock that make up the continents and the ocean floors, while the upper mantle is made of partially molten rock that is solid enough to be considered part of the lithosphere. Together, these layers define the lithosphere and contribute to the movement and interaction of tectonic plates on the Earth's surface.

Other combinations mentioned do not accurately define the lithosphere. The inner and outer cores are part of the Earth's deeper structure, and the lower mantle is much more ductile and not included in the lithosphere, which is characterized by its rigidity. Understanding the composition of the lithosphere is fundamental for studying Earth's geology and tectonic mechanics.