The World's Oceans
Oceans cover 71% of Earth and regulate climate.
About this topic
Oceans cover about 71% of Earth's surface and hold 97% of its water. The five oceans (Pacific, Atlantic, Indian, Southern, Arctic) are connected as one global ocean. The Pacific is the largest and deepest. Oceans absorb heat and CO₂, regulate climate, produce over half of our oxygen via phytoplankton and supply food.
They are essential for transport, trade and energy. Threats include pollution, overfishing, warming and acidification. Less than 25% of the sea floor has been mapped in detail.
A way to picture the ocean's size is that the Pacific alone is larger than all the land area on Earth put together, with an average depth of about 4 km. The average ocean depth is 3.7 km, and if Earth were shrunk to a billiard ball, it would still feel smooth and wet. The ocean stores about 1,000 times more heat than the atmosphere and has absorbed over 90 percent of the extra heat from global warming.
Phytoplankton are microscopic algae that produce around half of the oxygen we breathe and form the base of marine food webs. Seafood is a main source of protein for about 3 billion people, and shipping carries roughly 80 percent of world trade by volume. Offshore wind and wave energy and ocean minerals add to its value. The ocean also absorbs about a quarter of human CO2 emissions, which lowers its pH. A common misconception is that the oceans are separate; they are one connected system, and a molecule of water can move around it over centuries. Another is that the sea is well explored; we have better maps of Mars than the deep sea floor.
Key ideas
- Five oceans
- Average depth about 3.7 km
- Most heat is stored in the sea
Quick check
Use cases: where The World's Oceans helps
- Homework: review the key idea behind The World's Oceans before you start a problem set.
- Exam revision: use the quick check to test whether you can recall The World's Oceans without notes.
- Visual learning: play with the interactive lab to see how The World's Oceans changes when you adjust its inputs.
- Teaching a friend: explain The World's Oceans in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is The World's Oceans?
Oceans cover 71% of Earth and regulate climate.
What will I learn in The World's Oceans?
Five oceans. Average depth about 3.7 km. Most heat is stored in the sea.
Is The World's Oceans part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the The World's Oceans lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study The World's Oceans?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.