What is the lithosphere and how does it relate to earthquakes?

• A. The liquid layer beneath the crust.
• B. The hot, molten center.
• C. The rigid outer layer of Earth; earthquakes occur when stress is released in the lithosphere.
• D. The gaseous layer surrounding the planet.

Answer: (C)

The lithosphere is the rigid outer shell of Earth, made up of the crust plus the solid part of the upper mantle. It forms the tectonic plates that move very slowly on the softer layer beneath, called the asthenosphere. Earthquakes happen when these plates interact at their boundaries and stress builds up from sliding, colliding, or pulling apart. When enough stress accumulates, rocks break and slip along faults, releasing energy as seismic waves that shake the ground. So the lithosphere is where earthquakes originate because that brittle, rigid layer holds the faults and stores the stress that must be released. The other options describe layers that aren’t the lithosphere: a liquid layer beneath the crust is more like the asthenosphere, the hot molten center is the core, and the gaseous layer is the atmosphere.