Oceans

Just as interconnected landmasses have been divided into distinct nations that have changed throughout history, the world ocean has been divided into multiple oceans for various geographical, practical, and scientific reasons.

The Atlantic Ocean was named after Atlas, who was sentenced by Zeus in Greek mythology to hold up the sky, while the Pacific Ocean was named by Ferdinand Magellan as the 'peaceful sea' in 1520.

Earth's first oceans may have been as much as 230 degrees Celsius (446 degrees Fahrenheit), with the planet's thick atmosphere exerting sufficient pressure to prevent water from boiling at lower temperatures.

Ocean salinity comes primarily from eroded rocks, whose salts and minerals are carried into the sea by runoff, and from seawater dissolving salts and minerals from magma at seafloor openings.

Watch a visualization of global ocean currents from NASA's Estimating the Circulation and Climate of the Ocean project, which incorporates hundreds of millions of data points from satellites and floating sensors.

Surface ocean currents are primarily driven by wind, tides, and Earth's rotation, while deep-ocean currents are driven by differences in temperature and salt concentration that create vertical circulation.

The world's oceans, which have an average depth of 3.7 kilometers (2.3 miles), are often vertically divided into five zones based on depth or three zones based on the abundance of light.

Although an estimated 99.999% of the deep ocean has not been explored, techniques such as sonar have been used to identify the deepest known point in each of Earth's five oceans.

The warmest waters in the ocean are found at hydrothermal vents—hot springs on the seafloor that discharge plumes of mineral-rich water heated by magma to temperatures over 370 degrees Celsius (700 degrees Fahrenheit).

Take an interactive dive and see the animals that populate the oceans, from fish and coral near the surface to the cusk eel and hadal snailfish on the way down to the bottom of the Mariana Trench.