The oceans occupy more than 70 per cent or 364 million sq km (140 million square miles) of the earth’s total area of 510 million sq km (197 million square miles). They have tremendous development potential. Besides being a source of food – fish, mammals, reptiles, salt and other marine foodstuffs – the tides can be harnessed to provide power. The five main oceans of the earth are the Pacific, the Atlantic, the Indian, the Arctic and the Southern Oceans. They vary greatly in size, but by far the largest is the Pacific Ocean, which occupies nearly one-third of the world’s surface. The relative sizes of the world’s oceans are shown in Fig.12.2.

Oceanography, the science of the oceans, has become such an important subject in recent years that researches into the deep seas have been conducted by many institutions, universities, government ministries and other international organizations.

The most famous international oceanographic research centre is the International Council for the Exploration of the Sea with its headquarters in Copenhagen. Ocean exploration for the observation and recording of oceanographic data is a very expensive matter. It involves the operation and maintenance of specially equipped vessels in mid-ocean for long periods therefore large-scale oceanographic researches are thus best undertaken by international bodies. The older echo sounding techniques have now been replaced by radar sounding and electrical echo devices to find the precise depths of ocean floors and map the relief of the oceans.

Trained frogmen equipped with modern breathing apparatus are employed to gather valuable information from great depths. Deep-sea core samples are obtained by boring for the study of the oceanic deposits-the various kinds of oozes, muds and clays. Automatic-recording thermometers and other sensitive instruments can be lowered to any required depth by stationary vessels with laboratory facilities for processing any required data. For the observation and measurement of current flow, various kinds of current metres using propellers, vanes or pendulums have been designed.

Sealed bottles and other floating objects containing instructions for reporting their precise time and place of discovery are released in large numbers to compute the rate and direction of drift and current flow. Space photographs, satellite imageries and recording instruments carried in spacecrafts and satellites are also being used to monitor and map the oceans and their characteristics. With all these modern techniques at the disposal of the oceanographers, our knowledge of the mysteries of the oceans is greatly increased. But there is still much to be discovered.

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