Nature · Earth Science
The vast blue heart of the planet
The ocean is the continuous body of salt water that covers about 71 percent of Earth's surface and holds 97 percent of its water. Divided into five great oceans, it drives the climate, generates much of the oxygen we breathe and remains the least explored realm on the planet.
Earth's oceans filled billions of years ago from water vapour released by volcanoes and delivered by comets and asteroids. Their basins are shaped by plate tectonics: mid-ocean ridges create new seafloor that spreads outward and eventually plunges back into the mantle at deep trenches.
Down from the sunlit continental shelf, over the slope and abyssal plain to the deepest trenches — the hidden shape of the sea floor.
The bright surface layer of life
The uppermost layer where sunlight penetrates, powering the plankton that feed the entire ocean food web. Nearly all the sea's familiar creatures live here.
Dim waters between light and dark
Below the sunlit zone, light fades to a dim blue gloom. Creatures here often make their own light to hunt, hide and communicate in the near-darkness.
Rich waters over the continental shelf
Where the sea floods the edge of a continent, sunlit shallow water and nutrient-rich seabed create some of the world's richest fishing grounds.
The crushing, lightless abyss
At subduction zones the seafloor plunges into narrow trenches kilometres deep. Despite crushing pressure and total darkness, strange life still thrives there.