In subduction, what happens to the older, denser plate?

• A. It is pushed beneath the lighter plate and deep into the mantle.
• B. It rises to form mountain ranges.
• C. It splits into smaller plates.
• D. It remains at the same depth.

Answer: (A)

Subduction happens at convergent plate boundaries when a cooler, denser oceanic plate sinks beneath a lighter overriding plate. Because oceanic crust cools and becomes denser with age, the older portion is more prone to dive into the mantle. As it bends and descends, it moves deeper into the mantle, pulling the rest of the plate with it and creating features like deep ocean trenches and volcanic arcs inland from the boundary.

Rising to form mountains occurs mainly in continental-continental collisions, not when the older oceanic plate is subducting. Splitting into smaller plates isn’t a product of subduction, and staying at the same depth ignores the downward motion that characterizes subduction.