Where are most earthquakes concentrated?

• A. At plate boundaries, especially at subduction zones and along mid-ocean ridges.
• B. Uniformly distributed within plate interiors.
• C. Only at hotspots.
• D. Only at continental shields.

Answer: (A)

Earthquakes happen most where the rigid outer shell of the planet—the tectonic plates—interact with each other. The stresses produced by horizontal motion, collision, and pulling apart build up most strongly at plate boundaries. At subduction zones, one plate dives beneath another, creating intense friction and often very large earthquakes. Along mid-ocean ridges, plates are pulling apart and new crust forms, producing numerous faults that generate frequent earthquakes as they slip. Transform boundaries also shake as plates grind past one another. In contrast, the interiors of plates are relatively stable with fewer faults, so they experience far fewer earthquakes. Hotspots and continental shields aren’t the primary sites of seismic activity. So, most earthquakes are concentrated at plate boundaries, especially subduction zones and mid-ocean ridges.