In ocean-continent convergence, what happens to the ocean plate and what is the result?

• A. The ocean plate subducts beneath the continental plate, driving melting of the asthenosphere and potentially forming continental volcanoes such as those in the Cascade range
• B. The ocean plate overrides the continental plate, lifting the continent
• C. Two ocean plates collide to form island arcs only
• D. The plates move apart and create a new ocean basin

Answer: (A)

At ocean-continent convergence, the oceanic plate, being denser, sinks beneath the lighter continental plate. This subduction pulls the plate into the mantle, and the fluids released from the descending slab lower the melting point of the overlying mantle, generating magma. The magma then veins upward to form a continental volcanic arc, as seen in the Cascade range. The process also creates a deep ocean trench and is accompanied by strong earthquakes along the subduction zone. Other boundary types wouldn’t produce this setup: if the ocean plate were to override the continent, the dynamics would be opposite since oceanic lithosphere is dense; two ocean plates colliding produce island arcs within ocean basins, not continental volcanism; and plates moving apart create new ocean basins, not convergent subduction.