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Class 8 World Geography: Some Glimpses: cheat sheet
CBSE Social Science. The oceans, currents, trenches and coral reefs, why every map projection distorts, and key landforms of every continent.
Key ideas
- The ocean covers about 71% of the Earth and holds about 97% of its water.
- Oceans give almost half our oxygen through plankton, store heat and bring rain.
- Coral reefs shelter about a quarter of ocean species, but overfishing, pollution and warming cause bleaching.
- A warm current, the Gulf Stream, keeps the United Kingdom milder than other places at its latitude.
- A curved Earth cannot be shown flat without stretching, so every map distorts something.
- A gulf is a large inlet of the sea; a strait is a narrow channel joining two seas.
- Melting permafrost in the tundra releases gases that speed up climate change.
Remember
| Largest, deepest ocean / smallest | Pacific / Arctic |
| Deepest trench | Mariana Trench |
| Suez Canal | 1869: Red Sea to the Mediterranean |
| Third Pole | the Tibetan Plateau |
| Europe–Asia boundary | the Ural Mountains |
| Deserts | largest hot: Sahara; largest and coldest: Antarctica |
| Mercator projection | keeps shapes and directions; Greenland looks as big as Africa |
Watch out
- Believing the Mercator map shows true sizes: lands near the poles look far too big.
- Mixing up a gulf and a strait.
- Thinking a desert must be hot: Antarctica is the largest desert.
Worked example
A region of 71,000 square km is drawn on a map. (a) If it matched the Earth’s 71% ocean share, how much would be ocean? (b) How much land? (c) Give two ways oceans help life on Earth.
Working: 71% and 29% of 71,000
Answer: (a) 50,410 square km (b) 20,590 square km (c) They give much of our oxygen through plankton and control climate by storing heat and bringing rain.
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