Ocean Basin

Ocean basins are that part of Earth's surface that extends seaward from the continental margins, ranging from an average water depth of about 6,500 ft (2,000 m) down into the deepest trenches. The ocean basins constitute one of the two major topographic features of Earth's surface, the other being the continents. Ocean basins cover about 70% of the total sea area and about half of the planet's total surface area.

In contrast to the landforms of the continents so familiar to humans-features such as mountains, plateaus, hills, and rivers-the various topographic features of the ocean basins, the "oceanscape," are still not well understood by scientists. Some authorities claim that scientists know more about the surface of the Moon than they do about the ocean basins here on Earth. This situation exists because the ocean basins are thousands of meters below the water's surface, and they can be explored only with remote measuring equipment or, rarely, in special research submarines known as submersibles.

Among the things we do know about the ocean basins is that the familiar landscapes of continents are mirrored, and generally magnified, by comparable features in the ocean basin. The largest underwater mountains, for example, are higher than those on the continents, and underwater plains are flatter and more extensive than those on continents.

The basins of Earth's four oceans, the Atlantic, Pacific, Indian, and Arctic, differ from each other in many respects. Yet, they all contain certain common features that include oceanic ridges, trenches, and fracture zones and cracks, abyssal plains and hills, seamounts and guyots.