Unit 4

1. Unit 4 The importance of oceans Unit 4 The importance of oceans

2. Unit 4 The importance of oceans Where are the major oceans and seas?  361 million km² of the earth’s surface is covered by water.

3. Unit 4 The importance of oceans Where are the major oceans and seas? Oceans and seas occupy 71% of the earth’s surface. Oceans are unevenly distributed over the earth’s surface. Most of the southern hemisphere is covered by oceans. The four oceans are the Pacific, the Atlantic, the Indian and the Arctic.

4. Arctic Ocean North Sea °N Sea of Okhotsk Hudson Bay Baltic Sea Black Sea Yellow Sea Atlantic Ocean Caspian Sea Sea of Japan The Gulf Mediterranean Sea East China Sea Gulf of Mexico °N Pacific Ocean Caribbean Sea Red Sea Arabian Sea Bay of Bengal South China Sea ° Indian Ocean °S km N  Unit 4 The importance of oceans Where are the major oceans and seas?

5. Unit 4 The importance of oceans Pacific Ocean Pacific Ocean is the largest and deepest of the world’s four oceans, covering more than a third of the earth’s surface. The size of the Pacific Ocean is 165 000 000km², which is bounded on the east by the North and South American continents; on the north by Bering Strait; on the west by Asia; and on the south by Antarctica. The average depth of the ocean is about 4 282 m and the greatest depth is 11 033 m in the Mariana Trench. Much of the plant and animal life of the Pacific Ocean is concentrated along its margins.

6. Unit 4 The importance of oceans Atlantic Ocean Atlantic Ocean is the second largest of the earth’s four oceans and the most heavily travelled. The Atlantic Ocean has a surface area of 82 000 000 km². The Atlantic Ocean is an “S-shaped” north-south channel, extending from the Arctic Ocean in the north to the Antarctic continent in the south. It is situated between the western coast of the American continents and the eastern coasts of Europe and Africa. The Atlantic Ocean has an average depth of 3 926 m. The greatest depth is 8 742 m in the Puerto Rico Trench.

7. Unit 4 The importance of oceans Indian Ocean Indian Ocean is the third largest of the earth’s four oceans, bounded on the west by Africa, on the north by Asia, on the east by Australia, and on the south by Antarctica. The total area of the Indian Ocean is 73 400 000 km². The average depth is 4 210 m and the deepest point is 7 725 m, off the southern coast of the Indonesian island of Java. The Indian Ocean contains numerous islands, the largest of which are Madagascar and Sri Lanka. Tropical storms occur occasionally and the ocean is notable for seasonal winds called monsoons.

8. Unit 4 The importance of oceans Arctic Ocean Arctic Ocean is the smallest of the four world oceans. The Arctic Ocean extends south from the North Pole to the shores of Europe, Asia and North America. The total surface area of the Arctic Ocean is 14 000 000 km². The average depth is 1 500 m and the deepest point in the Arctic Ocean is 5 450 m in the Pole Abyssal Plain near the North Pole. Sea ice is formed by the freezing of seawater which is the most extensive form of ice in the Arctic Ocean. In winter a permanent cap of sea ice covers all of the ocean surface.

9. Unit 4 The importance of oceans Why are oceans important? Recreation Most of us are familiar with our beaches and seas as these are places for recreation. We go there for swimming in the hot summer season. They are also places for surfing, sailing and fishing.

10. Unit 4 The importance of oceans Why are oceans important? Trade and shipping Oceans have been used for transporting raw materials and manufactured products. Sea transport is the cheapest way of sending products in large quantity over a long distance.

11. Unit 4 The importance of oceans Why are oceans important? Trade and shipping Shipping routes link up industrial and densely populated regions in the world. Oceans are important as over 70% of world trade is carried out by ships.

12. Arctic Ocean °N Asia North America Europe Atlantic Ocean °N Africa Pacific Ocean ° Indian Ocean South America °S Australasia km Sea route N  Unit 4 The importance of oceans Major sea routes of the world

13. Unit 4 The importance of oceans Why are oceans important? Fish for food Oceans are rich in animal life. There are 20 000 species of fish in the oceans.

14. Unit 4 The importance of oceans Why are oceans important? Fish for food Fish is a major source of food, today fish supplies almost 20% of the world’s animal protein.

15. Unit 4 The importance of oceans Why are oceans important? Fish for food Fish caught are used for the making of animal feed, fertilizer, soaps and other commercial products. Millions of people depend upon fishing for their livelihood.

16. Unit 4 The importance of oceans Why are oceans important? Minerals Oceans are rich in minerals. Tin, gold, platinum and diamonds are found in the sand and gravel along the shore.

17. Unit 4 The importance of oceans Why are oceans important? Minerals Sea water is an important source of salt and fresh water.

18. Land Sea level 100 Fathoms Continental shelf Unit 4 The importance of oceans Why are oceans important? Energy Continental shelves are gently sloping plains beneath the sea bordering the continentals. They are no more than 100 fathoms (180m) deep.

19. Unit 4 The importance of oceans Why are oceans important? Energy Oceans are a potential source of renewable energy. Modern technology has made the mining of oil in the deep sea possible. It is possible to make use of sea waves and tidal currents for the generation of electricity.

20. Unit 4 The importance of oceans Why are oceans important? Ocean-atmosphere system Oceans act as a store house for the heat energy coming from the sun. The stored heat is then radiated back to the atmosphere thus keeping the atmosphere warm.

21. Sun More solar energy Atmosphere Less solar energy Ocean Surface Colder water Warmer water Colder water Arctic circle Antarctic circle Equator 66 1/2°N 0° 66 1/2°S Ocean absorbs sun’s energy Cold current Ocean warms the atmosphere and supplies it with moisture Warmer water flows to colder sea forming warm ocean current Warm current Colder water flows to warmer sea forming cold ocean current Unit 4 The importance of oceans The ocean-atmosphere system

22. Unit 4 The importance of oceans Why are oceans important? Ocean-atmosphere system  Our oceans supply the atmosphere with moisture and heat. The heat absorbed by the ocean is released to the atmosphere when air comes into contact with the ocean surface. The air also absorbs from the ocean its moisture. When this wet air blows onshore from ocean to land, it brings rain to coastal areas.

23. Unit 4 The importance of oceans Why are oceans important? Ocean currents and climate Difference in temperature leads to the different density of water over various parts of the ocean. The result is warmer water moves from tropical areas to polar areas while colder water moves from polar areas to tropical areas. Ocean currents influence the temperature of the coastal regions they flow past. A warm current raises the temperature of the coast while a cold current lowers it. The effect of the movement of ocean currents is important to our climate as it reduces the extremes in temperature of both the oceans and the atmosphere.

24. Arctic Ocean North Atlantic Drift Labrador Current °N Oya Siwo Asia North America Europe Gulf Stream Kuro Siwo California Current Canaries Current °N Africa Pacific Ocean Atlantic Ocean South Equatorial Current North Equatorial Current Agulhas Current South America Indian Ocean Brazil current Australasia East Australian Current °S Benguela Current Peruvian Current West Australian Current West Wind Drift Cold current Warm current km N  Unit 4 The importance of oceans Ocean currents of the world

25. Condensation to form clouds and rain Clouds Rain Wind moves up the slope and cools Wet on-shore wind Ocean Unit 4 The importance of oceans On-shore wind from ocean brings rain The air absorbs from the ocean its moisture. When this wet air blows on-shore from ocean to land, it brings rain to coastal areas.

26. Pacific Ocean Hong Kong Cool sea surface South China Sea Warm tropical air moves northwards Fog N  Unit 4 The importance of oceans Why are oceans important? Fog and typhoons In Hong Kong fog occurs in spring when warm air passes over the cold sea surface.

27. Condensation forms fog Warm tropical air move northwards South China Sea Sea surface still cool in spring Unit 4 The importance of oceans Why are oceans important? Fog and typhoons We receive a lot of rain in summer as winds blow in from the ocean.

28. Hong Kong Pacific Ocean Tropical sea supplies typhoons with heat and moisture Routes of typhoons N  Unit 4 The importance of oceans Why are oceans important? Fog and typhoons Typhoons affecting us in the summer season obtain their moisture and heat from the ocean. The heat produces an enormous amount of energy which makes these storms very destructive.

29. Unit 4 The importance of oceans Terms to learn Continental shelf (大陸架)-- a gently sloping plain beneath the sea bordering a continent. It is no more than 100 fathoms (180m) deep. Renewable energy (再生能源)-- energy that will never be used up. Sea waves and tidal currents are examples.