What feature is formed by subduction zones on the ocean floor?

• A. A mid-ocean ridge.
• B. A volcanic island chain.
• C. A trench.
• D. An oceanic plateau.

Answer: (C)

Subduction zones are convergent boundaries where one tectonic plate dives beneath another. As the downgoing plate sinks into the mantle, the overriding plate bends and the seafloor at that boundary is pulled down, creating a deep, elongated trough called a trench. This trench marks the boundary where the subducting plate meets the mantle, and it’s the defining feature formed directly by subduction on the ocean floor. Mid-ocean ridges form from seafloor spreading at divergent boundaries, not from subduction. Volcanic island chains can occur due to magma generated by the subducting slab, but the core surface feature produced by subduction itself is the trench. Oceanic plateaus arise from massive volcanic events elsewhere and are not the direct result of subduction zones.