During an earthquake, the energy stored in rocks and released as waves is primarily what type of energy?

• A. Kinetic energy in the moving rock
• B. Elastic potential energy
• C. Thermal energy
• D. Chemical energy

Answer: (B)

Strained rocks store elastic potential energy because the stresses from tectonic forces bend and compress minerals in the crust. As faults lock and blocks push against one another, the rocks deform elastically, meaning they try to snap back toward their original shape. That stored energy is released when the rocks rupture and rebound, sending out seismic waves that travel through Earth and cause ground shaking. The key idea is that the energy originates from the deformation itself—the elastic potential energy—rather than from motion after the release or from heat or chemical bonds. Some energy may later appear as heat from friction or as kinetic energy of moving rocks, but the primary source driving the quake’s energy release is the elastic potential energy stored in the stressed rocks.