Which type of plate boundary is associated with subduction and volcanic activity?

• A. Transform boundary
• B. Convergent boundary
• C. Divergent boundary
• D. Passive boundary

Answer: (B)

Convergent boundaries involve two tectonic plates colliding, with one plate sinking into the mantle in a subduction zone. This sinking slab releases water and other volatiles into the overlying mantle, lowering its melting point and generating magma. The magma rises to the surface to form volcanoes, often in a chain called a volcanic arc, and deep trenches form where subduction occurs. That combination—subduction and volcanic activity—is why this boundary type is the correct choice.

Transform boundaries slide plates laterally past one another, causing earthquakes but not typically subduction or volcanism. Divergent boundaries have plates moving apart, with magma rising to create new crust and volcanic activity at mid-ocean ridges, but there is no subduction. Passive boundaries are tectonically quiet margins with little subduction or volcanic activity.