When two oceanic plates meet at a convergent boundary, which plate subducts?

When two oceanic plates meet at a convergent boundary, which plate subducts?

• A. The older one
• B. The lighter one
• C. The denser one
• D. Both subduct

Answer: (C)

In ocean-ocean convergence, the sinking plate is the denser one. Oceanic lithosphere cools and becomes heavier as it ages, so the older, cooler plate has greater density. When the two plates collide, gravity pulls the denser slab down into the mantle, while the less dense, younger plate remains at the surface as the overriding plate. This subduction creates features like deep trenches and volcanic island arcs. The lighter plate wouldn’t subduct because buoyancy resists downward motion, and both subducting at once isn’t the typical outcome for a straightforward ocean-ocean collision.