Ocean basin

In hydrology, an oceanic basin (or ocean basin) is anywhere on Earth that is covered by seawater. Geologically, most of the ocean basins are large geologic basins that are below sea level. Most commonly the ocean is divided into basins following the continents distribution: the North and South Atlantic (together approximately 75 million km/ 29 million mi), North and South Pacific (together approximately 155 million km/ 59 million mi), Indian Ocean (68 million km/ 26 million mi) and Arctic Ocean (14 million km/ 5.4 million mi). Also recognized is the Southern Ocean (20 million km/ 7 million mi). All ocean basins collectively cover 67% of the Earth's surface, and together they contain almost 97% of all water on the planet. They have an average depth of almost 4 km (about 2.5 miles). Definitions of boundariesBoundaries based on continents"Limits of Oceans and Seas", published by the International Hydrographic Office in 1953, is a document that defined the ocean's basins as they are largely known today. The main ocean basins are the ones named in the previous section. These main basins are divided into smaller parts. Some examples are: the Baltic Sea (with three subdivisions), the Nort