Ocean

The ocean is the continuous body of salt water that covers roughly 70.8 percent of Earth's surface and holds about 97 percent of the planet's water. It is conventionally divided into the Pacific, Atlantic, Indian, Southern and Arctic oceans, which are in turn divided into smaller seas, gulfs and other bodies of water. The ocean basins themselves are shaped by plate tectonics: magma rising along mid-ocean ridges continually creates new seafloor and pushes tectonic plates apart, while subduction zones carry older oceanic crust back into the mantle and form deep trenches. Every ocean basin carries its own mid-ocean ridge, a submerged mountain range built by this spreading process, and the shape of the world oceans keeps changing as plate tectonics, post-glacial rebound and sea level rise reshape coastlines over time.