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? Unit 4 The importance of oceans 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.

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

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 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 m and the greatest depth is 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  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 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 m. The greatest depth is m in the Puerto Rico Trench. 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 km². The average depth is m and the deepest point is 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  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 km². The average depth is m and the deepest point in the Arctic Ocean is 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. Unit 4 The importance of oceans  We go there for swimming in the hot summer season. They are also places for surfing, sailing and fishing.

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

Why are oceans important? Unit 4 The importance of oceans Fish for food Oceans are rich in animal life. There are species of fish in the 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 and 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? Continental shelves are gently sloping plains beneath the sea bordering the continentals. They are no more than 100 fathoms (180m) deep. Energy Unit 4 The importance of oceans Sea level 100 Fathoms Continental shelf Land

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 Unit 4 The importance of oceans Sun Less solar energy Ocean More solar energy Warmer water Equator Colder water Arctic circleAntarctic circle 0°66 1 / 2 °N66 1 / 2 °S Surface Cold current Warm current 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 Atmosphere

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

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

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

Hong KongPacific Ocean Tropical sea supplies typhoons with heat and moisture Routes of typhoons  N 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. Unit 4 The importance of oceans

Terms to learn Continental shelf ( 大陸架 )  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 )  Renewable energy ( 再生能源 ) -- energy that will never be used up. Sea waves and tidal currents are examples. Unit 4 The importance of oceans