OCEANOGRAPHY THE PACIFIC OCEAN BY PROF. A. BALSUBRAMANIAN OUTLINE 1.0 Introduction 1.1 Geographic setting 1.2 Dimension 1.3 Depth 1.4 Principal Arms 1.5 Volume of water 2.0 Historical explorations 3.0 Crustal plates 4.0 Profile of the ocean floor 4.1 Continental shelf 4.2 Continental slope 4.3 Submarine canyons 4.4 Deep ocean floor 4.5 Abyssal plains/hills 4.6 Ring of Fire 4.7 Mid ocean ridges 4.8 Deep ocean trenches 4.9 Seamounts 4.10 Guyots 4.11 Icebergs 4.12 Active volcanoes 4.13 Islands or island arcs 5.0 Sedimentation 6.0 Water masses and Temperature 6.1 Salinity 6.2 Density 7.0 Climate 7.1 Water circulation and Ocean Currents 7.2 Oceanic currents 7.3 Ocean waves 8.0 Ecological zones 8.1 Marine fauna 8.2 Marine flora 8.3 Marine sediments 9.0 Economic mineral resources 9.1 Commerce and shipping 9.2 Ports and terminals 10.0 Marine pollution 10.1 Hazards 1 The Objectives After attending this lesson, the learner should be able to comprehend about the geographic setting of the Pacific ocean, its dimension, associated water masses, morphological features of the ocean floor, very significant conditions of the ocean, sediments, marine life, marine pollution and other hazards. In addition the user should be able to understand, the importance of the Pacific in the context of global activities including the historical oceanographic explorations. 1.0 Introduction The world’s oceanic water masses occupy about 97 per cent of the hydrosphere. The remaining three percent, is frozen in the form of icecaps and distributed in the lakes, rivers, subsurface aquifer, and as water vapour. The seas and oceans cover about 70% of the surface of the Earth, which is equal to 361.1 million sq.km in area. One water body as a whole: Oceanic water masses are fully connected and interlinked with each other. If we physically look at these, there is only one water mass existing in the world. The presence of various continents, divide the world’s water mass into five major oceans. They are, the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Arctic ocean and the Antarctic ocean. Water Tentacles: Each one of these large oceans, include many smaller water bodies as seas, gulfs, or bays and straits. Among these, the Pacific Ocean is the largest and the deepest ocean in the world. Understanding of the oceanography of the Pacific, is an interesting topic. 1.1 Geographic Setting The name “Pacific”, is derived from the Latin term "Mare Pacificum", which means "peaceful sea". Geographically, the Pacific Ocean alone covers about 32% of the Earth's surface. The surface area of the Pacific ocean is greater than that of all land areas put together. The Pacific extends from the Arctic of the north pole to the Antarctic regions of the south pole. This ocean is bounded by the North and South America on the east. It is bounded by Asia, Japan, Australia and the new Zealand on the west. The Pacific Ocean is known for its enormous biological resources and geological features. Links with other water masses: The Pacific ocean is linked with the other water masses through straits and passages. a) It is linked with the Arctic Ocean through the Bering Strait. b) It is linked with the Atlantic Ocean through the Drake Passage at the southern end of South America, Straits of Magellan, and finally, through the Panama Canal. c) The Pacific Ocean is linked with the Indian Ocean through the passages like Malay Archipelago, Torres strait existing between Australia and Papua New Guinea. 1.2 Dimension The Pacific is a very vast ocean, covering individually, about 165 million sq.km. Along with its other marginal seas, the it covers an area of about 180 million square kilometers. Its maximum length along the north –south direction is about 14,500 km. Its maximum width along the east-west direction, is about 17,700 km. That is seen between the Isthmus of Panama and the Malay Peninsula. It extends approximately 15,500 kilometres from the Bering Sea, in the North pole, to the southern tip of the globe. The Pacific has its greatest, east-west width, at about 5 degree North latitude. It stretches for about 19,800 kilometres from Indonesia to the coast of Colombia and Peru. This distance itself, is halfway across the world. 2 The Equator and International Date Line: The equator subdivides the Pacific ocean into the North Pacific Ocean and South Pacific Ocean. The Pacific ocean is a historically significant part in the world. The Pacific plays its role in classifying the World Time Zones. The 180 degree meridian passes through the Pacific. It is called as the international date line. It is where each day begins 1.3 Depth The Pacific Ocean is the deepest ocean, in the world. The mean depth is 4280 m. Its greatest depth, lies within the Mariana Trench and the Japan Trenches. These two are the world ‘s deepest trenches, reaching a depth of more than 10 km. The Mariana Trench lies in the western North Pacific ocean with a depth of 10,911 metres below sea level. The deepest parts of the Pacific are also very closer to the shores of land masses. They include the Japan and Kuril trenches, which border the island chains of the Western Pacific. 1.4 Principal Arms The water tentacles of the pacific and called as oceanic arms.The principal arms of the Pacific Ocean are a) the Bering Sea in the north ; b) the Gulf of California in the east c) the Ross Sea in the south; and d) the Sea of Okhotsk, the Sea of Japan, and the Yellow sea, East China sea, South China sea, Philippine sea, Coral sea, and Tasman sea in the west. 1.5 Volume of water The total volume of all oceanic waters, in the globe, is about 1370 million cubic kilometers. Out of which, the volume of water existing in the pacific Ocean is about 714.410 million cubic.km. This is about 53% of the total volume of water of all the oceans put together. Much of the freshwater to the Pacific also comes from a few large rivers like the Columbia of North America and the Huang He, Chang (Yangtze) of China. 2.0 Historical Explorations About 3000 years ago, seafarers started their voyages in the oceanic world. The famous and remarkable ancient explorations were started by the Greeks, Chinese, Europeans, Romans, Asians, the British and the Portuguese. The Portuguese explorer, Ferdinand Magellan, named this great oceanic water mass, as the Pacific Ocean. Explorations and Migrations: The Ocean Explorations had several reasons to the study of the Pacific Ocean, in depth. The early migrants have crossed the long distances of the open Pacific ocean, using primitive boats. The islands of the south and west Pacific, were populated by migrants. Most of them were from the Asia. The European travellers, including Marco Polo, had reported an ocean off Asia, in the late 15th century. Some trading ships had also sailed around Africa to the western rim of the Pacific, during this time. Sixteenth Century Explorations: The true recognition of the Pacific, as a distinct ocean, from that of the Atlantic Ocean, came after Balboa's sighting of its eastern shore, during the year 1513. Magellan's crossing of the Philippines, during the year 1520-21, initiated a series of explorations. The notable ones were, the explorations of Drake, Tasman, Dampier, Cook, Bering, and Vancouver. These went upto the end of the 18th century. 3 All these explorations had mainly disclosed the nature of the coastline and the major islands of the Pacific to the other parts of world. In the 16th century, the supremacy in the Pacific region was shared by both Spain and Portugal. After Seventeenth Century: The English and the Dutch have established the footholds in the Pacific, during the 17th century. The France and Russia have done some expeditions during the 18th century. The people of Germany, Japan, and the United States have done their works during the 19th century. The Pacific Ocean has its own history in the history of the world. It is because of these world famous voyages and explorations of Pacific Islanders, it was possible to acquire all practical knowledge about oceanography, over these years. Ferdinand Magellan: The 1494, the Line of Demarcation was done to establish the boundary between the Atlantic and Pacific Oceans. The Portuguese and the Spanish together explored the vastness of the Pacific Ocean over a period of time. In 1520 , Ferdinand Magellan conducted an expedition with three ships . They sailed out of the stormy passage of the strait at the southern tip of South America into the Pacific Ocean. It was Megellan who named the Pacific as a peaceful, calm, quiet ocean. Magellan's voyages were followed by several voyages from the western coasts. Other explorers: The Dutch Explorations are also very notable ones. Dutch explorers looked mainly for profit in the Pacific ocean for its trade. The British also did notable Explorations of the Pacific. In 1765, Byron sailed into the Pacific Ocean and declared that two northern islands were belonging to the British. They are the Tuamotu Islands and Pukapuka in the northern Cook Islands. In 1768, Captain James Cook (1728–1779) sailed on his first voyage to the Pacific. Cook proved that the two islands of New Zealand were definitely not part of some larger southern continent. They are independent. Inputs from the Explorations: The people of the ancient explorations, gave the details of the major oceanic currents, prevailing wind patterns, and the other features of the Pacific.