What are important ocean floor features and how do they form?

• A. Trenches form at divergent boundaries; mid-ocean ridges arise at subduction zones; seamounts from erosion; ocean floor maps record plate tectonics.
• B. Trenches form at subduction zones; mid-ocean ridges arise at divergent boundaries; seamounts from volcanic activity; ocean floor maps record plate tectonics.
• C. Seamounts form at subduction zones; trenches arise at divergent boundaries; ridges are created by erosion; ocean floor maps record plate tectonics.
• D. Ocean floor is uniform; trenches and ridges are mythical; no seamounts exist.

Answer: (B)

On the ocean floor, plate tectonics shapes three main features: trenches, mid-ocean ridges, and seamounts. Trenches form where one tectonic plate dives beneath another at subduction zones, creating deep, narrow troughs. Mid-ocean ridges appear along divergent boundaries where plates move apart; rising magma solidifies to form new crust, creating a continuous global ridge system. Seamounts are underwater volcanoes built by volcanic activity, rising from the seafloor and not formed by erosion. Mapping the ocean floor with sonar and other methods reveals these features and their global pattern, which supports plate tectonics.