Which geological process is associated with deep earthquakes and magmatic activity at plate boundaries?

• A. Transform fault motion at strike-slip boundaries.
• B. Divergent boundary spreading at mid-ocean ridges.
• C. Mantle plume upwelling beneath plates.
• D. Subduction at convergent boundaries.

Answer: (D)

Subduction at convergent plate boundaries is the process that brings deep earthquakes together with magmatic activity. When one plate sinks beneath another, the descending slab ruptures and sends earthquakes that can occur at great depths, forming a dipping Wadati-Benioff zone. At the same time, fluids released from the subducting slab lower the melting point of the overlying mantle, generating magma that rises to form volcanic arcs on the overriding plate. This combination of deep seismicity and arc volcanism is a hallmark of subduction zones, setting it apart from transform boundaries (where earthquakes are typically shallow), divergent boundaries (which create new crust with relatively shallow activity), or mantle plumes (hotspot volcanism away from plate edges).