The ocean is the giant body of salt water that covers most of our planet. It is one connected body of water, but for convenience we split it into five named oceans: Pacific, Atlantic, Indian, Arctic and Southern. Together they cover more than 70% of Earth's surface and contain over 90% of the space where life on Earth can live.
- Named Oceans5Pacific, Atlantic, Indian, Arctic, Southern
- % of Earth Covered71%by all oceans combined
- % of Earth's Water96.5%is salty ocean water
- Average Depth3,688 mapprox. 11 Eiffel Towers stacked
- Deepest Point10,935 mMariana Trench, Pacific
- Average Temp4 °Cthe deep sea is always cold
How big is each ocean?
Area in millions of square kilometres:
The Pacific Ocean alone is bigger than every continent on Earth put together. The Arctic is the smallest ocean, and the only one that freezes over.
What is an ocean?
An ocean is a very large body of salt water. The water in the ocean is salty because for billions of years rivers have been washing tiny amounts of salt out of the rocks on land and carrying it down to the sea. The water evaporates back into the sky as rain, but the salt is left behind.
What lives in the ocean
The ocean is home to creatures of every size, from microscopic plankton (which produce half the oxygen we breathe) to the blue whale (the largest animal that has ever lived on Earth). Coral reefs are sometimes called the rainforests of the sea because of the huge variety of life they support.
Oceans and the weather
Oceans run the weather of the whole planet. They store heat from the Sun and move it around the world in huge currents like the Gulf Stream (which keeps Britain much warmer than it would otherwise be) and the Humboldt (which keeps Chile cool). Hurricanes and typhoons are powered by warm ocean water.
Threats to the ocean
Plastic pollution, overfishing, oil spills, and climate change all damage the ocean. Warmer water bleaches coral reefs. Acidic water (caused by carbon dioxide soaking in from the air) weakens shells. Plastic kills millions of seabirds, turtles, and whales every year.
Deeper dive: zones of the ocean
Scientists divide the ocean into vertical layers, each with very different conditions.
- Sunlight zone (top 200 metres). Bright enough for plants to grow. Most ocean life lives here.
- Twilight zone (200 to 1,000 metres). Dim blue light only. Many creatures here make their own light.
- Midnight zone (1,000 to 4,000 metres). Totally dark and very cold.
- Abyss (4,000 to 6,000 metres). The flat ocean floor. Cold, dark, and crushingly high pressure.
- Trenches (below 6,000 metres). Deep cracks in the ocean floor. The Mariana Trench reaches 10,935 metres down.
Pick an ocean below to find out more.