Which feature are long, narrow depressions on the seafloor?

• A. Abyssal plains
• B. Continental shelf
• C. Ocean trenches
• D. Mid-ocean ridge

Answer: (C)

Long, narrow depressions on the seafloor are ocean trenches. They form where one tectonic plate sinks beneath another at convergent boundaries, a process called subduction. As the plate dips down, it creates a deep, elongated trench that follows the edge of the sinking plate. Trenches are among the deepest parts of the ocean, reflecting intense vertical depth at these subduction zones. In contrast, abyssal plains are broad, flat regions, the continental shelf is the shallow, submerged edge of a continent, and mid-ocean ridges are underwater mountain ranges where new crust forms, featuring a central rift valley rather than a deep, narrow trench.