Unit 4 The importance of oceans Unit 4

Unit 4 The importance of oceans

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.

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.

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

Unit 4 The importance of oceans 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 km², 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.

Unit 4 The importance of oceans 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 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.

Unit 4 The importance of oceans 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.

Unit 4 The importance of oceans 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 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.

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.

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.

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.

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

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.

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.

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.

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 gravel along the shore.

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

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 (180 m) deep. Land Sea level 100 Fathoms Continental shelf

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.

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.

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

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.

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.

Unit 4 The importance of oceans Ocean currents of the world t if r c. D N o West Wind Drift Cold current Warm current km lf u G ea r t S ren t cur Peruvian Current °N Atlantic Ocean South America zil Indian Ocean East Australasia Australian West Australian Current °N m Bra w Si ya O ent urr as C ulh Ag Canaries Current K Pacific Ocean North Equatorial Current Benguela Current South Equatorial Current S urr Africa North America a. C rni o ur o iw lifo Europe Ca Asia r rado Lab rent Cur th r No la t A Arctic Ocean nti °S

Unit 4 The importance of oceans On-shore wind from ocean brings rain Condensation to form clouds and rain Clouds 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. Rain Wind moves up the slope and cools Wet on-shore wind Ocean

Unit 4 The importance of oceans Why are oceans important? N Fog and typhoons In Hong Kong fog occurs in spring when warm air passes over the cold sea surface. ace Hong Kong f r su a l se o Co South China Warm tropical air Sea moves northwards Pacific Ocean Fog

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. Condensation forms fog Warm move tropical a ir north ward s South China Sea surface still cool in spring

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. Hong Kong N Pacific Ocean Tropical sea supplies typhoons with heat and moisture Routes of typhoons

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 (180 m) deep. Renewable energy (再生能源) -- energy that will never be used up. Sea waves and tidal currents are examples.