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Home , Abyssal plain, Continental margin, Continental shelf, East Pacific Rise, Guyot, Marine pollution

OCEANOGRAPHY

THE PACIFIC

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 2.0 Historical explorations 3.0 Crustal plates 4.0 Profile of the ocean floor 4.1 4.2 Continental slope 4.3 Submarine 4.4 Deep ocean floor 4.5 Abyssal /hills 4.6 4.7 Mid ocean ridges 4.8 Deep ocean 4.9 4.10 4.11 Icebergs 4.12 Active volcanoes 4.13 or arcs 5.0 6.0 Water masses and Temperature 6.1 Salinity 6.2 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 9.0 Economic mineral resources 9.1 Commerce and shipping 9.2 Ports and terminals 10.0 Marine 10.1 Hazards

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The Objectives

After attending this lesson, the learner should be able to comprehend about the geographic setting of the , its dimension, associated water masses, morphological features of the ocean floor, very significant conditions of the ocean, sediments, , 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, , subsurface aquifer, and as water vapour. The and cover about 70% of the surface of the , 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 , divide the world’s water mass into five major oceans. They are, the Pacific Ocean, the , the , the ocean and the Antarctic ocean.

Water Tentacles: Each one of these large oceans, include many smaller water bodies as seas, gulfs, or bays and . Among these, the Pacific Ocean is the largest and the deepest ocean in the world. Understanding of the 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 ". 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 on the east. It is bounded by , , and the 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 through the Bering . 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 , Torres strait existing between Australia and .

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 of Panama and the Malay . It extends approximately 15,500 kilometres from the , in the North pole, to the southern tip of the globe. The Pacific has its greatest, east-west width, at about 5 degree North . It stretches for about 19,800 kilometres from Indonesia to the of Colombia and Peru. This distance itself, is halfway across the world.

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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 and the Japan Trenches. These two are the world ‘s deepest trenches, reaching a depth of more than 10 km. The lies in the western North Pacific ocean with a depth of 10,911 metres below . The deepest parts of the Pacific are also very closer to the 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 of California in the east c) the in the south; and d) the Sea of Okhotsk, the , and the Yellow sea, East China sea, , Philippine sea, sea, and Tasman sea in the west.

1.5 Volume of water

The total volume of all oceanic , 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 and the Huang He, Chang () 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 , 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.

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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 and Russia have done some expeditions during the 18th century. The people of Germany, Japan, and the 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 .

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 . 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. It was due to these voyagers, we could get the details of a) equatorial countercurrent, b) the great northern whirl, c) the great southern whirl, and d) forecasting of all wind .

3.0 Crustal plates

According to the theory of , the earth's outer shell consists of huge rigid plates. The plates are of two types as oceanic plates and continental plates. Although continental plates are located under the continents, they usually extend into the ocean as well. Only small continental plates, like the Turkish-Aegean Plate, do not extend into the ocean. Oceanic plates are located under the oceans. There are three major oceanic plates. The smallest of the three, the , is located west of . The largest plate is the . It spans over most of the Pacific ocean. The third one is the . It is located west of South America.

Plate tectonics:

The plates were initially together. The Plates move away from one another along the divergent plate boundaries. At the same time they must move toward one another along the convergent plate boundaries, elsewhere. As the plates move, they carry the ocean floor and the continents with them. The relative

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movement of two neighbouring plates is generally about 1 to 10 centimetres a year. When two plates collide each other, one plate may pile up against the other. This created the underwater . Sometimes, one plate may be drawn down into the under another plate. Such action produces deep oceanic trenches and generate volcanic eruptions. may also occur near these plate boundaries.

Impacts : Different movements of the plates have different effects on the ocean bottom. Sea-floor spreading--and the formation of new sea floors--occur where the plates move apart. The mid-ocean ridges also mark the existence of such zones. The Pacific Ocean is currently shrinking due to the theory of plate tectonics. It shrinks by roughly an inch per year (2–3 cm/yr) on 3 sides. It amounts to an average of 0.5 square km a year, the ocean is shrinking.

4.0 Profile of the ocean floor

The ocean floor is a region of spectacular morphology and contrasting relief features. Beneath the sea there are broad plains, towering chains, undersea volcanoes, deep trenches and valleys. The morphology of the pacific consists of a vast continental shelf, continental slope and a deep ocean basin.

4.1 Continental shelf

The continental shelf is the submerged land at the edge of the continents. It begins at the shoreline and gently slopes underwater to an average depth of about 120 to 130 metres. The width of the continental shelf averages 75 kilometres. The edge of the continental shelf occurs extends to a depth of 20 to 550 m, averaging 130 m. The continental shelves of the Pacific, consist of huge deposits of , mud, and . There is a vast thicknesses of consolidated sedimentary rocks, overlying crystalline rocks. The edge of the shelf is called as the shelf break. It is characterised by an abrupt increase in the slope to an average of about 4 degrees.

4.2 Continental slope

The Continental shelf is followed by the Continental Slope. The slope is much steeper than the shelf and plunges to a depth of about 3.6 kilometres. The Continental slope forms the sides of the continents. The width ranges from 20 to 100 kilometres. In many places, deep underwater canyons gash the slope. One of the most surprising findings of the early oceanographers was that the deepest parts of the oceans are not at the centers. They are quite close to the margins of continents, particularly in the Pacific Ocean. The continental slope of the Pacific is very close to the coastlines, in almost the all surrounding countries of the Pacific.

4.3 Submarine canyons

A lot of Submarine canyons are found cutting across the shelf and slope. They are often extending from the mouths of the terrestrial rivers. The valleys may be 12m deep. The maximum depth may go up to 300m. The following are the notable submarine canyons of the Pacific Ocean: 1) Bering 2) 3) Navarin Canyon 4) Pribilof Canyon 5) Scripps Canyon and 6) Zhemchug Canyon.

4.4 Deep ocean floor

The deep ocean floor begins at the seaward edge of the continental slope and rise. Deep-sea peaks, valleys, and plains lie beyond the . The thickness of Sediments, in the oceans,

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averages about 450 metres. The cover in the Pacific ocean basin ranges from 300 to 600 metres. The deep-sea sediments can reveal much about the earth’s history of the last 200 million years. They show the evidences for various processes, including , the history of ocean life, the behaviour of Earth’s magnetic field, the changes in the oceanic currents and paleoclimate. The ocean basins are transient features over geologic time, changing shape and depth while the process of plate tectonics occurs.

4.5 Abyssal plains/hills

An abyssal is an underwater plain on the deep ocean floor. It is usually found at depths from 3,000 meters to 6,000 meters. The abyssal plains are among the flattest, smoothest and least explored regions on Earth. The abyssal plains occupy a significant portion of the deep ocean basin. The abyssal plains cover nearly 75% of the Pacific ocean floors. They are formed by the of fine sediment carried by currents. These sediments have covered and smoothed out the irregularities in the morphology of the ocean floor. The flatness of these plains is due to the result of the accumulation of a blanket of sediments, up to 5 kilometers in thickness. These overlie the basaltic rocks of the oceanic . The thick sediment deposits extend up to a distance of about 1,000 kilometres inside the sea from the slope.

4.6 Ring of Fire

The Pacific is the oldest of the existing ocean basins. Its oldest rocks have been dated at about 200 million years. The Pacific basin is referred to as the “Ring of Fire” due to intense and volcanic activity occurring near areas of tectonic plate .

4.7 Mid ocean ridges

The mid-ocean ridges form a chief feature of the deep ocean basin. The ridges consist of a chain of mountains that runs about 60,000 kilometres through the three major oceans. Scientists discovered the mountain chain independently in each ocean and gave it different names, including Mid-Atlantic Ridge, East Pacific Rise, and Mid-Indian Ridge. Most mountains of the mid-ocean ridges stand about 1,500 metres above the sea floor. Deep valleys cut across the ridges in many places, producing a rugged, fractured surface. Frequent volcanic activity occurs along such central valleys.

The Pacific Rises:

The East Pacific Rise is a mid-ocean ridge. It extends from the to a point west of the southern tip of South America. It rises to an e levation of 2,130 meters above the ocean floor. Along the East Pacific Rise, molten rocky upwells from Earth's mantle , adding crust to the plates on each side of the rise.

4.8 Deep Ocean Trenches

An ocean trench is a long, deep in the ocean floor. These trenches are one of the most striking features of the Pacific floor. Deep-sea trenches generally lie seaward of and parallel to the island arcs or mountain ranges of the continental margins. Trenches virtually encircle the rim of the Pacific basin. The trenches have lengths of thousands of kilometres, They are generally of hundreds of kilometers in width. They extend up to 3 to 4 km deeper, as valleys, within the surrounding ocean floor.

4.9 Trenches of the Pacific Ocean

The notable trenches of the Pacific Ocean are: 1. Mariana Trench 2. 3. Phillipine Trench

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4. Kuril-Kamchatka Trench 5. 6. Izu-Ogasawara Trench 7. 8. Yap Trench 9. Peru- Trench 10.Aleutian Trench 11.Middle America Trench 12. 13.Vityaz Trench and 14.Ryukyu Trench.

4.9 Seamounts

A is an underwater mountain, rising from the ocean seafloor. It does not reach to the oceanic water's surface or sea level. They do not form islands. These are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to an elevation of 1,000 to 4,000 metres. The smaller submarine volcanoes are called sea knolls. The Pacific Ocean contains several long seamount chains. They are formed by . These include the two major seamount chains as, the Hawaiian – Emperor seamount chain and the Louisville seamount chain. Bathymetric Profiles from the Pacific, have shown that there are about 10,000 seamounts existing with more than 1 Km elevation.

4.10 Guyots

The -topped seamounts are called as guyots. They are named after Arnold Henri (1807-1884), the Swiss-born American and geographer. Guyots are isolated submarine volcanic mountains with a flat summit of more than 200 metres below the sea surface. The flat tops may have diameters greater than 10 km. Guyots are most abundant In the Pacific Ocean. Their summits lie 1,000 to 2,000 metres, below sea level.

4.11 Icebergs

An iceberg is a large piece of frozen ice that has broken off from a or an and is floating freely in open water. Icebergs generally range from 1 to 75 metres above sea level and weigh 100,000 to 200,000 metric tons. The term "iceberg" most likely got originated from the Dutch term "ijsberg", which means ice mountain. There are very few such features in the Pacific as they are mostly in the north and pacific nearer to the poles.

4.12 Active volcanoes

There are active volcanoes in every part of the world. There are about 1,500 active volcanoes, many in them are located in the Pacific Ocean. The Pacific rim's "Ring of Fire" is an arc around the Pacific Ocean where there are 400 and more volcanoes. The Ring of Fire is composed over 75% of the world's active and dormant volcanoes. The ring is about 40,000km long.

4.13 Islands or island arcs

The Pacific contains about 25,000 islands. Many of them are concentrated in the south and west. It is more than the total number in the rest of the world's oceans combined. The majority of these islands are found south of the equator. Most of the Pacific Islands lying south of the Tropic of Cancer are collectively referred to as Oceania. In the southwestern corner of the Pacific lie the islands of Melanesia, dominated by New Guinea. Other important island groups of Melanesia include the Bismarck Archipelago, Fiji, New Caledonia, the Solomon Islands and .

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Types of islands:

Islands in the Pacific Ocean are of four basic types as, continental islands, high islands, coral reefs, and uplifted coral platforms. Continental islands lie outside the Andesite line and include New Guinea, the islands of New Zealand, and the Philippines. Some of these islands are structurally associated with nearby continents. High islands are of volcanic in origin, and many contain active volcanoes. Among these are Bougainville, Hawaii, and the Solomon Islands. The third and fourth types of islands are both originated due to coral-growth. Coral reefs are low-lying underwater structures that have built up on the basaltic flows of the ocean's surfaces. One of the most dramatic is the Great Barrier off the northeastern Australia.

5.0 Sedimentation

The distribution of sediments in the oceans is controlled by five primary factors: 1. Age of the underlying crust 2. Tectonic history of the ocean crust 3. Structural trends in basement 4. Nature and location of sediment source, and 5. Nature of the sedimentary processes delivering sediments to the basins.

6.0 Water masses and Temperature

The volume of the Pacific Ocean is approximately 622 million cubic km. Water temperatures in the Pacific vary from freezing in the poleward areas to about 30 °C (86 °F) near the equator. Salinity also varies with reference to . The water near the equator is less salty than that one found in the mid- latitudes because of abundant equatorial precipitation throughout the year. Because the vast majority of the world ocean's volume , the mean temperature of is low.

About 75% of the ocean's volume has a temperature from 0° – 5°C . The same percentage falls within a salinity range between 34–35 ppt. The Surface temperatures can range from below freezing point near the poles to 35°C in restricted tropical seas, while the salinity can vary from 10 to 41 ppt. The western tropical Pacific has the warmest surface waters.

6.1 Salinity

The salinity of sea water, denoted by the symbol O/OO, is defined as the number of grams of salts contained in 1000 grams of sea water. Sea water is about a 3.49% salt . The more saline, the denser the seawater. As the range of salt concentration in the ocean varies from about 3.2 to 3.8%, oceanographers refer to salt content as 'salinity'.

Three major factors influence salinity (salt concentration) in Pacific Ocean aters. They are precipitation,evaporation and winds. Around the equator, where there is large amounts of rainfall, the surface water salinity rarely exceeds 34 parts per thousand. The lowest salinity in water occurs in the extreme northern regions of the Pacific, near the Bering Sea. Here, the salt concentrations are often less than 32 parts per thousand.

6.2 Density

Ocean water gets more dense as temperature goes down. So, the colder the water, the more dense it is. Increasing salinity also increases the density of sea water. The density of ocean water is rarely measured directly. The measured density values are on the average to ±4.3 × 10−6 g cm−3.

The density of water in the Pacific were found to be −6 −3 a) ±3.8 to ± 3.0 × 10 g cm from 0 to 490m depth zones, −6 −3 b) 12.5 ±4.2 × 10 g cm from 490 to 1000 m depth zones and

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−6 −3 c) 17.6 ± 2.6 × 10 g cm from 1000 to 5834 m depth zones. In the deep waters, the measured values of density are equal to 6 × 10−6 g cm−3 .

7.0 Climate of the Pacific

The Climate of the Pacific is greatly influenced by the following: 1) planetary air pressure systems 2) trade winds and westerly winds 3) tropical cyclones (hurricanes & typhoons) 4) continental influences and the 5) monsoonal - a rainy .

Effects on Climate:

The planetary air pressure systems and resultant wind patterns exhibit remarkable uniformity in the climate of the south and the east. The trade winds and westerly winds are well-developed patterns, modified by seasonal fluctuations. Tropical cyclones (hurricanes) may form south of from June to October and affect Mexico and Central America. The continental influences cause climatic uniformity to be much less pronounced in the eastern and western regions at the same latitude in the North Pacific Ocean. The western Pacific is monsoonal with a rainy season occurring during the summer months, when moisture-laden winds blow from the ocean over the land. The tropical cyclones (typhoons) may strike southeast and east Asia from May to December.

7.1 Water circulation and Ocean Currents

The waters of the pacific ocean move constantly. Two types of circulation create the currents in the ocean. They are: (1) wind-driven circulation and (2) . Wind-driven circulation results from the wind blowing on the ocean surface. Wind-driven currents move in enormous circular patterns called gyres.

Surface Circulation

The surface circulation of the oceans is intimately tied to the prevailing wind circulation of the atmosphere. Major circulation of water in these gyres is clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. The circulation of ocean waters is vitally important in dispersing heat energy around the globe. In general, heat flows toward the poles in the surface currents, while the displaced cold water flows toward the equator in deeper ocean layers.

Thermohaline Circulation Thermohaline circulation refers to the deepwater circulation of the oceans. It is primarily caused by differences in density between the waters of different regions. Wind systems: There are two major wind systems driving the waters of the Pacific ocean. They are the westerlies and the trade winds. The Westerlies lie about 40−50° latitude in both the hemispheres. They are called as the “roaring forties” and the trade winds come from the east which dominate in the region between 20°N and 20°S.

7.2 Oceanic currents

Huge whirls, formed by the major ocean currents, are found roughly north and south of the equator. The chief currents of the North Pacific, beginning at the equator, are the North Equatorial , Kuroshio (Japan Current), North Pacific Current, or Drift, and California Current. The south equatorial current and the Antarctic circumpolar current, both are belonging to the South pacific currents.

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7.3 Ocean waves

Scientists have discovered waves that rise up to be taller than some sky scrapers. The ocean waves, which are also known as internal waves, form at the boundary between two layers of water with different in a deep ocean trench in the South Pacific Ocean. The highest waves are found to be as much as 15 to 20 m.

8.0 Ecological zones

The first appearance of life on the earth is thought to have occurred in the oceans , in about 2 or 3 billion years ago. Biological oceanography is an important aspect of all oceans. The modern marine environment of oceanic waters, is divided into two major realms as the benthic realm and the pelagic realm. These are classified based upon the ecological characteristics and marine life associated with them. The Pacific ocean has an incredible variety of living things. These marine life ranges in size from microscopic one- celled to the blue , which may measure up to 30 metres long. They are divided into three groups as the , , and the .

The Benthic Realm

The benthic realm refers to the floor of the oceans, extending from the high line to the greatest ocean depths. The organisms that live in or on the bottom are called benthos. The benthic realm is subdivided on the basis of depth into the , which extends from high tide to a depth of about 200 m, and the deep-sea realm. The benthic life forms are both sessile (attached) and motile (mobile). Some benthonic life forms live by predation. Many others live on the from the water. Some others scavenge the bottom for organic that are available inside. Benthonic can live only in the euphotic zone, the uppermost 100–200 m of the ocean, where penetrates. Benthonic animals that live below the euphotic zone.

The Pelagic Realm

The pelagic realm consists of all of the ocean water covering the benthic realm. It is divided horizontally into two zones as neritic (fertile near-shore)province and the oceanic province. Vertically it is divided into the euphotic, or photic, zone and the aphotic (without sunlight) zone. Drifting, free-floating organisms, called plankton, and organisms with poor mobile ability populate the euphotic zone. Most plankton are microscopic or near-microscopic in size. Heterotrophic plankton () are also floating animals and protozoans of the sea, rely on the as food sources. and are the dominant protozoan. Many juvenile forms of swimmers (such as shrimp) or bottom dwellers (such as barnacles) pass through a planktonic phase. Marine organisms capable of self-locomotion are called nektonic life forms. , , and are examples of marine nekton.

8.1 Marine fauna

The ocean is home to countless numbers of plants and animals. Most of the Ocean's life requires sunlight, many ocean plants float on the surface of ocean waters or live on the ocean floor in shallow water. These plants provide food, protection and habitats for many marine animals. Some plants are also sources of vitamins and minerals for people.

Marine Life in the Pacific Ocean

Fish are the most important animals of the nekton. About 13,300 kinds of fish live in the ocean. are free-swimming molluscs (animals with soft, boneless bodies) that have 10 arms.

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Nektonic mammals include , manatees, , and whales, all of which remain in the ocean all their lives. Other marine mammals, such as sea lions, sea otters, seals, and , spend time on land. The Pacific's greatest asset is its fish. The shoreline waters of the continents and the more temperate islands yield herring, , sardines, snappers, swordfishes, and tuna, as well as shellfish.

8.2 Marine flora

The ocean is a complex environment that is home to many types of plant . Plants found in the ocean provide a basic source of food and shelter for marine life. The kinds of plants found in the ocean are of two basic types as those that have roots and those that do not have any roots. Most plants need sunlight, water and in to grow. Many plants also thrive in the ocean habitat. The most famous plants are: 1. Seaweed 2. 3. Phytoplankton 4. 5. Red 6. Coralline Algae.

8.3 Marine sediments

The thickest deposits of sediment on Earth are on the ocean floor. In the oceans, it piles up to 8 km in thickness. The thickest build up of sediments are found on the continental rises and slopes. Ocean sediments are basically small insoluble of rocks, soil, volcanoes, chemicals and organic bodies. They are delivered into the ocean from lands via rivers, streams and lakes. These particles are of different sizes and volumes, and are commonly present on the shores of oceans.

Types of sediments in oceans:

There are four major types of ocean sediments, which are composed by different organic and inorganic materials. These include a) Hydrogenous Sediments, b) Biogenous Sediments, c) Lithogenous Sediments And d) Cosmogenous Sediments.

Hydrogenous Sediments: Hydrogenous sediments are usually found near the hydrothermal vents where metal ions are released into the water. They combine with the silica and become a dark, metal-rich sediment. Other forms of hydrogenous sediments are nodules, , carbonates and salts and ammonia. The hydrogenous sediments are the result of chemical reactions between hydrogenous minerals of the oceans and rivers, or are simply created during the precipitation process (or condensation process) of the ocean's water in changing climatic conditions.

Biogenous Sediments:

The biogenous sediments are the hard and insoluble remains of organic life on sea and land (like bone particles). The Biogenous is a kind of pelagic marine sediment. It contains remnants of living organisms, mostly plankton. The plankton that forms this sediment comes from species that have shells made of and . For phytoplankton, the plant-like photosynthesizers, have calcite shells and have siliceous or opal shells. Zooplankton, the animal element, produce foraminifera that have calcite shells and radiolaria composed of siliceous or opal shells.

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Lithogenous Sediments: The lithogenous sediments are tiny particles from rocks, volcanic eruptions, metal ores and various other natural elements. grains are found in lithogenous marine sediment as well as lithogenous . Lithogenous clay is termed pelagic clay if more than 70 percent of it has lithogenous sediment in its dry mass. The Ocean floors in the deepest parts of the Pacific Ocean are predominately composed of lithogenous sediment. In the central ocean basins, the largest component of lithogenous sediment is clay.

Cosmogenous Sediments:

The cosmogenous sediments are tiny meteorites and specks, which are extraterrestrial in nature.

9.0 Economic mineral resources

The exploitation of the Pacific's mineral wealth is hampered by the ocean's great depths. In shallow waters of the continental shelves off the coasts of Australia and New Zealand, and natural are extracted. Pearls are harvested along the coasts of Australia, Japan, Papua New Guinea, Nicaragua, Panama, and the Philippines. The mineral wealth of the ocean extends to the deep-sea floor. Deposits near undersea hot springs contain , , and .

Mineral resources of the Pacific Ocean

The shallow continental shelves have been exploited as a source of and gravels. In addition, extensive deposits of petroleum-bearing sands have been exploited in offshore areas, particularly along the Gulf and California coasts of the United States and in the . On the deep ocean floor manganese nodules, formed by the precipitation of manganese oxides and other metallic salts around a nucleus of or shell, represent a potentially rich and extensive resource. Ocean water is processed to extract commercially valuable minerals such as salt, bromine, and magnesium. A lthough nearly 60 valuable chemical elements are found to have been dissolved in ocean water. Most of them are in dilute concentrations. Due to this, their commercial extraction is not profitable. 9.1 Commerce and shipping

The ocean has been a highway for trade since people built the first ships thousands of years ago. Today, transportation--especially of heavy and bulky products--remains an important use of the ocean. Most of the transpacific sea-lanes pass through the . Since the 1950s , many of the South Pacific islands have become world famous tourist centers.

Waterways along the Pacific:

Strategically important access waterways along the Pacific include the a) La Perouse, b) Tsugaru, c) Tsushima, d) Taiwan, e) Singapore, and f) Torres Straits.

9.2 Ports and terminals

Ports and terminals of the pacific Ocean are: Bangkok (Thailand), Hong Kong (China), Kao-hsiung (Taiwan),

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Los Angeles (US), Manila (Philippines), Pusan (South ), San Francisco (US), Seattle (US), Shanghai (China), Singapore, Sydney (Australia), Vladivostok (Russia), Wellington (NZ), and Yokohama (Japan).

10.0 Marine pollution

Problems of the Pacific Ocean:

Marine pollution is a generic term for the harmful entry into the ocean of chemicals or particles. The Pacific is no exception to all kind of entering into the sea. Oil is a major source of ocean pollution. Most oil pollution enters the ocean from oil spills on land or in rivers used to petroleum. The world's largest accidental occurred in June 1979, when an oil well blew out off the east coast of Mexico and spilled about 490 million litres of oil.

Ocean Dumping:

Ocean dumping is yet another problem of the Pacific. The deliberate dumping of products into it is another major source of ocean pollution. Such products include and . Industries dump chemicals, animal and plant matter, and other pollutants. Throughout the history, have been directly or indirectly influenced and benefitted by the oceans.

10.1 Hazards

The Pacific is surrounded by a zone of violent volcanic and earthquake activity. The pacific is also subjected to frequent tropical cyclones (typhoons) in southeast. Tropical cyclones (hurricanes) may form south of Mexico and strike Central America and Mexico from June to October. Cyclical El Nino/La Nina phenomenon occurs in the equatorial Pacific, influencing weather in the Western Hemisphere and the western Pacific. Ships are subjected to superstructure icing in extreme north from October to May. Persistent in the northern Pacific can be a maritime hazard from June to December. Most strike land areas in or bordering the Pacific Ocean. Fortunately, scientists can predict how fast a is moving and are able to warn people in its path.

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