Almost three-fourths of the Earth's surface is covered with water, which is why it appears blue from space and is called the ‘blue planet’. The largest water bodies are oceans, while large continuous expanses of land are continents. There are five oceans — the Pacific (largest), Atlantic, Indian, Southern (Antarctic) and Arctic (smallest) — and although shown with boundaries on maps, they are all interconnected. Most ocean water is salty; freshwater is only a tiny share, found in glaciers, rivers, lakes and underground. The Indian Ocean is bordered by Asia, Africa and Australia, with the Arabian Sea and the Bay of Bengal on either side of India. Continents can be counted in different ways — from four to seven — but the seven-continent count (Asia, Africa, North America, South America, Antarctica, Europe, Australia) is the most widely used. Islands are smaller landmasses surrounded by water; Greenland is the largest, and India has over 1,300 islands including the Andaman and Nicobar and the Lakshadweep groups. Oceans regulate climate, send the monsoon rains, and their flora produces over half the world's oxygen, earning them the name ‘planet's lungs’. They can also cause disasters such as cyclones and tsunamis (as in 2004), and are now threatened by plastic pollution and overfishing.
Distribution of water and landThe five oceans and their interconnectionContinents and how they are countedIslands of the world and of IndiaOceans, climate, life and disasters
Key terms
Ocean
A very large body of salt water; there are five oceans, all interconnected.
Continent
A large continuous expanse of land; the most common count is seven continents.
Island
A piece of land smaller than a continent and surrounded by water on all sides.
Marine flora and fauna
The plant life (algae, seaweed) and animal life (fish, dolphins, whales) found in oceans.
Tsunami
A huge, powerful ocean wave usually caused by an undersea earthquake or volcanic eruption.
Freshwater
Water that is not salty, found in glaciers, rivers, lakes, the atmosphere and as groundwater.
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