Which boundary is associated with volcanic activity along the edge of a continent (the overriding plate in an oceanic-continental setting)?

Which boundary is associated with volcanic activity along the edge of a continent (the overriding plate in an oceanic-continental setting)?

• A. Oceanic-Oceanic Convergent
• B. Oceanic-Continental Convergent
• C. Continental-Continental Convergent
• D. Divergent

Answer: (B)

Subduction at an oceanic-continental convergence boundary drives volcanism right along the edge of the continent. The oceanic slab sinks beneath the continental plate, and as it descends it releases water and other volatiles into the overlying mantle. Those fluids lower the melting point of the mantle wedge, generating magma. This magma, being buoyant, rises to the surface and feeds volcanoes that form a volcanic arc along the continental margin. That’s why the volcanic activity sits at the edge where the oceanic plate meets the continent. In contrast, other boundary types don’t produce volcanism in the same way at the continental edge: oceanic-oceanic convergence forms volcanic island arcs rather than continental margins, continental-continental convergence mainly builds mountains with little volcanism, and divergent boundaries create volcanism at rifts or mid-ocean ridges rather than along a continent’s edge.

Subduction at an oceanic-continental convergence boundary drives volcanism right along the edge of the continent. The oceanic slab sinks beneath the continental plate, and as it descends it releases water and other volatiles into the overlying mantle. Those fluids lower the melting point of the mantle wedge, generating magma. This magma, being buoyant, rises to the surface and feeds volcanoes that form a volcanic arc along the continental margin. That’s why the volcanic activity sits at the edge where the oceanic plate meets the continent.

In contrast, other boundary types don’t produce volcanism in the same way at the continental edge: oceanic-oceanic convergence forms volcanic island arcs rather than continental margins, continental-continental convergence mainly builds mountains with little volcanism, and divergent boundaries create volcanism at rifts or mid-ocean ridges rather than along a continent’s edge.