Which term means a break in the Earth's crust where earthquakes occur?

• A. Faulting
• B. Unconformity
• C. Intrusion
• D. Extrusion

Answer: (A)

Faulting describes fractures in the Earth's crust where rocks on either side move past one another. These faults are the cracks along which stress from plate tectonics is released, producing earthquakes when the rocks slip. The other terms refer to different geological concepts: an unconformity is a gap in the rock record caused by erosion or a lull in deposition; an intrusion is magma that moves into existing rock and hardens underground; an extrusion is lava that erupts onto the surface and solidifies. So the break in the crust where earthquakes occur is the fault, and the act of forming or existing as a fault is faulting.