Perhaps the most striking feature that characterizes the deep ocean floor is the vast oceanic ridge system that encircles the Earth along tectonic plate boundaries.
Although it comprises more than half of Earth's surface area, the deep ocean floor was a region of near total mystery until fairly recently. Even now, efforts to map ocean basins are in their infancy.
For large stretches the deep ocean basin is flat. But seamounts, guyots, island arcs and trenches, all of which result at least in part from tectonic activity, break up the sameness.