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PACIFIC OCEAN, the largest body of water in the world, an area of ​​which is estimated at 178.62 million km 2, which is several million square kilometers more than the Earth's land area and more than twice the area of ​​the Atlantic Ocean. The width of the Pacific Ocean from Panama to the eastern coast of Mindanao is 17,200 km, and the length from north to south, from the Bering Strait to Antarctica, is 15,450 km. It stretches from the western shores of North and South America to the eastern coasts of Asia and Australia. From the north, the Pacific Ocean is almost completely enclosed by land, connecting with the Arctic Ocean by a narrow Bering Strait (minimum width 86 km). In the south, it reaches the shores of Antarctica, and in the east, its border with the Atlantic Ocean is drawn along 67 ° W. - Cape Horn meridian; in the west, the border of the South Pacific Ocean with the Indian Ocean is drawn at 147 ° E, corresponding to the position of the South-East Cape in southern Tasmania.

Zoning of the Pacific Ocean.

Usually the Pacific Ocean is divided into two regions - North and South, bordering on the equator. Some specialists prefer to draw the boundary along the axis of the equatorial countercurrent, i.e. approximately 5 ° N latitude. Previously, the water area of ​​the Pacific Ocean was often subdivided into three parts: northern, central and southern, the borders between which were the Northern and Southern tropics.

Individual parts of the ocean located between islands or land ledges have their own names. The largest areas of the Pacific Basin include the Bering Sea in the north; the Gulf of Alaska in the northeast; the bays of California and Tehuantepec in the east, off the coast of Mexico; Fonseca Bay off the coast of El Salvador, Honduras and Nicaragua, and slightly to the south - the Gulf of Panama. There are only a few small bays off the west coast of South America, such as Guayaquil off the coast of Ecuador.

In the western and southwestern Pacific, numerous large islands separate many inter-island seas from the mainland, such as the Tasman Sea southeast of Australia and the Coral Sea off its northeastern coast; The Arafura Sea and Carpentaria Bay north of Australia; the Banda Sea to the north of Timor Island; the Flores Sea to the north of the island of the same name; The Java Sea north of Java; The Gulf of Thailand between the peninsulas of Malacca and Indochina; Bakbo Bay (Tonkin) off the coast of Vietnam and China; Makassar Strait between the islands of Kalimantan and Sulawesi; the Moluccan and Sulawesi seas, respectively, to the east and north of the Sulawesi island; finally, the Philippine Sea east of the Philippine Islands.

A special area in the southwest of the northern half of the Pacific Ocean is the Sulu Sea within the southwestern part of the Philippine archipelago, where there are also many small bays, bays and semi-enclosed seas (for example, the Sibuyan, Mindanao, Visayan Seas, Manila Bay, Lamon Bays and Pour). The East China and Yellow Seas are located off the eastern coast of China; the latter forms two bays in the north: Bohaiwan and West Korean. The Japanese Islands are separated from the Korea Peninsula by the Korea Strait. In the same northwestern part of the Pacific Ocean, several more seas are distinguished: the Inland Sea of ​​Japan among the southern Japanese islands; The Sea of ​​Japan to the west of them; to the north - the Sea of ​​Okhotsk, connected with the Sea of ​​Japan by the Tatar Strait. Farther north, directly south of the Chukotka Peninsula, is the Anadyr Bay.

The greatest difficulties are caused by drawing the border between the Pacific and Indian Oceans in the area of ​​the Malay Archipelago. None of the proposed boundaries could satisfy botanists, zoologists, geologists and oceanologists at the same time. Some scholars consider the so-called. the Wallace Line through the Makassar Strait. Others propose to draw the border through the Gulf of Thailand, the southern part of the South China Sea and the Java Sea.

Characteristics of the shores.

The shores of the Pacific Ocean vary so much from place to place that it is difficult to distinguish any common features. With the exception of the extreme south, the Pacific coastline is surrounded by a ring of dormant or occasionally active volcanoes known as the Ring of Fire. Most of the shores are formed by high mountains, so that the absolute elevations of the surface change abruptly at a close distance from the coast. All this indicates the presence of a tectonically unstable zone along the periphery of the Pacific Ocean, the slightest movement within which is the cause of strong earthquakes.

In the east, the steep slopes of the mountains approach the very shore of the Pacific Ocean or are separated from it by a narrow strip of the coastal plain; this structure is characteristic of the entire coastal zone, from the Aleutian Islands and the Gulf of Alaska to Cape Horn. Only in the extreme north does the Bering Sea have low-lying shores.

In North America, in the coastal ridges there are isolated low areas and passages, but in South America the majestic Andes chain forms an almost continuous barrier throughout the continent. The coastline is fairly flat, and bays and peninsulas are rare. In the north, Puget Sound and San Francisco Bays and the Strait of Georgia are most deeply cut into the land. On most of the South American coastline, the coastline is flattened and almost nowhere forms bays and bays, with the exception of the Gulf of Guayaquil. However, in the extreme north and extreme south of the Pacific Ocean, there are areas very similar in structure - the Alexander archipelago (southern Alaska) and the Chonos archipelago (off the coast of southern Chile). Both areas are characterized by numerous islands, large and small, with steep shores, fjords and fjord-like straits that form secluded bays. The rest of the Pacific coast of North and South America, despite its great length, presents only limited opportunities for navigation, since there are very few convenient natural harbors, and the coast is often separated by a mountain barrier from the interior of the mainland. In Central and South America, mountains hinder communication between west and east, isolating a narrow strip of the Pacific coast. In the north of the Pacific Ocean, the Bering Sea is ice-bound for most of the winter, and the coast of northern Chile is largely desert; the area is known for its deposits of copper ore and sodium nitrate. Areas located in the far north and far south of the American coast - the Gulf of Alaska and the vicinity of Cape Horn - have gained notoriety for their stormy and foggy weather.

The western coast of the Pacific Ocean differs significantly from the eastern one; the coasts of Asia have many bays and bays, in many places forming an unbroken chain. There are numerous protrusions of various sizes: from such large peninsulas as Kamchatka, Korean, Liaodong, Shandong, Leizhoubandao, Indochina, to countless capes separating small bays. Mountains are also confined to the Asian coast, but they are not very high and are usually somewhat removed from the coast. More importantly, they do not form continuous chains and are not a barrier isolating coastal areas, as is the case on the east coast of the ocean. In the west, many large rivers flow into the ocean: Anadyr, Penjina, Amur, Yalujiang (Amnokkan), Huang He, Yangtze, Xijiang, Yuanjiang (Hongha - Red), Mekong, Chao Phraya (Menam). Many of these rivers have formed vast deltas where large populations live. The Yellow River carries so much sediment into the sea that its sediments have formed a bridge between the coast and a large island, thus creating the Shandong Peninsula.

Another difference between the eastern and western coasts of the Pacific Ocean is that the western coast is bordered by a huge number of islands of different sizes, often mountainous and volcanic. These islands include the Aleutian, Commander, Kuril, Japanese, Ryukyu, Taiwan, Philippine islands (their total number exceeds 7000); finally, between Australia and the Malacca Peninsula there is a huge cluster of islands, in area comparable to the mainland on which Indonesia is located. All these islands have mountainous terrain and are part of the Ring of Fire that encircles the Pacific Ocean.

Only a few large rivers of the American continent flow into the Pacific Ocean - this is hindered by mountain ranges. The exception is some rivers in North America - Yukon, Kuskokwim, Fraser, Columbia, Sacramento, San Joaquin, Colorado.

Bottom relief.

The Pacific Ocean depression has a fairly constant depth throughout the entire area - approx. 3900–4300 m. The most remarkable elements of the relief are deep-water depressions and trenches; uplifts and ridges are less pronounced. Two uplifts stretch from the shores of South America: the Galapagos in the north and the Chilean, stretching from the central regions of Chile to about 38 ° S latitude. Both of these uplifts join and continue south towards Antarctica. As another example, a rather vast underwater plateau can be mentioned, over which the Fiji and Solomon Islands rise. Deep-sea trenches are often located close to the coast and parallel to it, the formation of which is associated with the belt of volcanic mountains that frame the Pacific Ocean. The most famous are the Challenger deep-water troughs (11,033 m) southwest of Guam; Galatea (10,539 m), Cape Johnson (10,497 m), Emden (10,397 m), three Snellus troughs (named after a Dutch ship) with depths from 10,068 to 10,130 m and Planet trough (9788 m) near the Philippine Islands; Ramapo (10,375 m) south of Japan. The Tuscarora depression (8513 m), which is a part of the Kuril-Kamchatka trench, was discovered in 1874.

A characteristic feature of the Pacific Ocean floor is the numerous seamounts - the so-called. guyots; their flat tops are located at a depth of 1.5 km or more. It is believed that these are volcanoes, which previously rose above sea level, were subsequently washed away by waves. To explain the fact that they are now at great depths, one has to assume that this part of the Pacific Basin is experiencing subsidence.

The Pacific Ocean bed is composed of red clays, blue silts and crushed coral fragments; some vast areas of the bottom are covered with globigerin, diatom, pteropod, and radiolarian oozes. The bottom sediments contain manganese nodules and shark teeth. There are a lot of coral reefs, but they are only common in shallow waters.

The salinity of water in the Pacific Ocean is not very high and ranges from 30 to 35 ‰. Temperature fluctuations are also quite significant depending on latitudinal position and depth; the temperatures of the near-surface layer in the equatorial belt (between 10 ° N and 10 ° S) are approx. 27 ° C; at great depths and in the extreme north and south of the ocean, the temperature is only slightly above the freezing point of sea water.

Currents, tides, tsunamis.

The main currents in the North Pacific include the warm Kuroshio Current, or the Japanese Current, passing into the North Pacific (these currents play the same role in the Pacific Ocean as the system of the Gulf Stream and the North Atlantic Current in the Atlantic Ocean); cold California current; North Passat (Equatorial) current and cold Kamchatka (Kuril) current. In the southern part of the ocean, the warm currents of the East Australian and South Passat (Equatorial) currents are distinguished; cold currents of the West Winds and the Peruvian. In the Northern Hemisphere, these main systems of currents move clockwise, and in the Southern - against it. The tides are generally low for the Pacific Ocean; the exception is Cook Bay in Alaska, which is famous for its exceptionally high water rise during high tides and is second only to the Bay of Fundy in the northwest Atlantic Ocean in this respect.

When earthquakes or large landslides occur on the seabed, waves - tsunamis - occur. These waves travel huge distances, sometimes more than 16 thousand km. In the open ocean, they are low in height and long, but when approaching land, especially in narrow and shallow bays, their height can increase up to 50 m.

Research history.

Navigation in the Pacific Ocean began long before the beginning of the written history of mankind. However, there is evidence that the first European to see the Pacific Ocean was the Portuguese Vasco Balboa; in 1513 the ocean opened before him from the Darien Mountains in Panama. In the history of Pacific exploration, there are such famous names as Fernand Magellan, Abel Tasman, Francis Drake, Charles Darwin, Vitus Bering, James Cook and George Vancouver. Later, scientific expeditions on the British ship "Challenger" (1872-1876), and then on the ships "Tuscarora", played an important role. "Planet" and Discovery.

However, not all seafarers who crossed the Pacific Ocean did it on purpose, and not all were well equipped for such a voyage. It could well be that winds and ocean currents picked up primitive boats or rafts and carried them to distant shores. In 1946, the Norwegian anthropologist Thor Heyerdahl put forward a theory according to which Polynesia was settled by settlers from South America who lived in Peru in pre-Inca time. In support of his theory, Heyerdahl with five satellites sailed almost 7 thousand km across the Pacific Ocean on a primitive raft made of balsa logs. However, although his voyage, which lasted 101 days, proved the possibility of such a voyage in the past, most oceanographers still do not accept Heyerdahl's theories.

In 1961, a discovery was made indicating the possibility of even more striking contacts between the inhabitants of the opposite shores of the Pacific Ocean. In Ecuador, in a primitive burial at the Valdivia site, a fragment of pottery was discovered that is strikingly similar in design and technology to the pottery of the Japanese Islands. Other pottery items have also been found, belonging to these two spatially separated cultures, and also having a noticeable similarity. According to archaeological data, this transoceanic contact between cultures, located at a distance of about 13 thousand km, occurred approx. 3000 BC.

The Pacific Ocean is not only the largest in area, but also the deepest of all oceans. It has the most complex bottom topography compared to other oceans. Measurements show that changes in depths up to 2000 m and more can be observed at a distance of several miles. Numerous very diverse forms of lowering the bottom give way to sharp uplifts, often protruding above the ocean surface in the form of chains, groups, ridge of islands. In terms of the number of islands, the Pacific Ocean ranks first among other oceans.

Another most characteristic feature of the relief of the Pacific Ocean floor is the presence in it of a large number of narrow elongated deep-water depressions located mainly in its western part along chains or groups of islands.

The main deep-water depressions of the Pacific Ocean are as follows.

I. Aleutian depression - located south of the Aleutian ridge of islands, with depths reaching 7678 m. 212

2. The Kuril Basin stretches from Kamchatka along the Kuril Islands, with depths of more than 10,370 m.

3. The Japanese Basin is located east of the Japanese Islands, with depths exceeding 10,550 m.

4. The Mariana Trench is located east and south of the Mariana Islands chain. In it, Soviet scientists in 1958 discovered a depth of 11,034 m. This depth is the greatest for the entire World Ocean.

5. The Philippine Basin, or the Mindanao Basin, is located east of the Philippine Islands and has a maximum depth of 10,540 m.

6. The Bougainville Trench is located between New Guinea and the Solomon Islands, with depths reaching 9,140 m.

7. The Tonga Basin is located east of the Tonga Islands, with a maximum depth of 10,633 m.

8. The Karmadsk depression lies to the east of the Kermadek Islands, with depths of more than 9400 m.

9. The Atacama Basin is located off the coast of Chile and Peru, with a maximum depth of 7634 m.

In addition, there are a large number of separate vast basins with depths over 5000 m and small basins in area exceeding 6000 and even 7000 m.

The next characteristic feature of the underwater topography of the bottom of the Pacific Ocean is a chain of seamounts, most often with flat peaks, located in the area between the Hawaiian, Mariana and Marshall Islands.

There are also various underwater rises of the Pacific Ocean floor. The main ones are the East Pacific Rise, which stretches to the west towards the Indian Ocean, and the New Zealand sill, which stretches from the slope of the Antarctic continent to New Zealand. The depths above these uplifts generally vary from 2000 to 3000 m, and in some places decrease to 500 m.

Topic 6. SUBJECT OF STUDYING THE GEOGRAPHY OF MATERIALS AND OCEANS. OCEANS.

OCEANS

PACIFIC OCEAN

Features of the structure of the ocean floor

The ocean floor has a complex geological structure. Much of the Pacific Ocean lies on one lithospheric plate, which interacts with other plates. Deep-sea trenches and island arcs adjoin the zones of their interaction. An almost continuous chain of active volcanoes - the Pacific Ring of Fire - is connected with the system of deep-sea trenches and mountain structures on the continents and islands that surround the ocean.

Unlike other oceans, the continental shelf of the Pacific Ocean is only 10% of its total area. The deepest troughs are Mariana (11,022 m) and Philippine (10,265 m).

The ocean floor makes up over 65% of the seabed area. It is crossed by numerous underwater mountain ranges. At the bottom of the hollows, volcanic hills and mountains are widely developed, including flat-topped mountains (gayoti) and faults.

The Pacific Ocean is the deepest. Its bottom relief is complex. The shelf (continental shelf) occupies a relatively small area. Off the coast of North and South America, its width does not exceed tens of kilometers, and off the coast of Eurasia, the shelf is measured in hundreds of kilometers. Deep-sea trenches are located in the marginal parts of the ocean, and the main part of the deep-sea trenches of the entire World Ocean is located in the Pacific Ocean: 25 out of 35 have a depth of more than 5 km; and all the troughs with a depth of over 10 km - there are 4 of them.

Large uplifts of the bottom, individual mountains and ridges divide the ocean floor into hollows. In the southeast of the ocean, the East Pacific Rise is located, which is part of the global system of mid-ocean ridges.

An almost continuous chain of active volcanoes forming the Pacific Ring of Fire is associated with the system of deep-sea trenches and mountain structures on the continents and islands adjacent to the ocean. In this zone, ground and underwater earthquakes are also frequent, causing giant waves - tsunamis.

128. Climatic conditions over the Pacific Ocean. The Pacific Ocean, stretching through almost all latitudinal climatic zones, reaches its greatest width in the tropics and subtropics, which is why the tropical and subtropical climate prevails here.

Deviations in the location of climatic zones and local differences within them are caused by the peculiarities of the underlying surface (warm and cold currents) and the degree of influence of the adjacent continents with the atmospheric circulation developing above them. The main features of atmospheric circulation over the Pacific Ocean are defined by five areas of high and low pressure. In the subtropical latitudes of both hemispheres over the Pacific Ocean, two dynamic high pressure regions are constant - the North Pacific, or Hawaiian, and South Pacific maximums, the centers of which are located in the eastern part of the ocean.

At near-equatorial latitudes, these areas are separated by a constant dynamic area of ​​reduced pressure, developed more strongly in the west. To the north and south of the subtropical maxima at higher latitudes there are two minima - the Aleutian minima centered over the Aleutian Islands and the Antarctic minima stretching from east to west in the Antarctic zone. The first exists only in winter in the Northern Hemisphere, the second - throughout the year. Subtropical highs determine the existence in the tropical and subtropical latitudes of the Pacific Ocean of a stable system of trade winds, consisting of the northeastern trade winds in the Northern Hemisphere and the southeastern ones in the South.

The trade wind zones are separated by the equatorial calm belt, which is dominated by weak and unstable winds with a high frequency of calm. The Northwest Pacific is a distinct monsoon region. In winter, the northwestern monsoon prevails here, bringing cold and dry air from the Asian mainland, in summer - the southeastern monsoon, carrying warm and humid air from the ocean. Monsoons disrupt the trade wind circulation and lead to the overflow of air from the Northern Hemisphere to the Southern Hemisphere in winter, and in the opposite direction in summer.

129. Waters of the Pacific Ocean: physical and chemical properties, dynamics of water masses. The distribution of the salinity of the Pacific Ocean waters obeys general laws. In general, this indicator at all depths is lower than in other oceans of the world, which is explained by the size of the ocean and the significant remoteness of the central parts of the ocean from the arid regions of the continents. The ocean water balance is characterized by a significant excess of the amount of atmospheric precipitation together with the river runoff over the amount of evaporation.

In addition, in the Pacific Ocean, in contrast to the Atlantic and Indian, at intermediate depths there is no inflow of especially saline waters of the Mediterranean and Red Sea types. The centers of the formation of highly saline waters on the surface of the Pacific Ocean are subtropical regions of both hemispheres, since evaporation here significantly exceeds the amount of precipitation. Both highly saline zones (35.5% o in the north and 36.5% o in the south) are located above 20 ° latitude of both hemispheres. ...

North of 40 ° N NS. salinity decreases especially rapidly. At the top of the Gulf of Alaska, it is 30-31% o. In the Southern Hemisphere, the decrease in salinity from the subtropics to the south slows down due to the influence of the current of the West Winds: up to 60 ° S. NS. it remains more than 34% o, while off the coast of Antarctica it decreases to 33% o.

Water freshening is also observed in equatorial-tropical regions with a large amount of atmospheric precipitation. Between the centers of salinization and freshening of waters, the distribution of salinity is strongly influenced by currents. Along the shores, the currents carry freshened waters from high latitudes to lower latitudes in the east of the ocean, and saline waters in the west in the opposite direction.

Thus, the isohaline maps clearly show the "tongues" of freshened waters that come from the California and Peruvian currents. The most common pattern of changes in the density of waters in the Pacific Ocean is an increase in its values ​​from the equatorial-tropical zones to high latitudes. Consequently, the decrease in temperature from the equator to the poles completely covers the decrease in salinity throughout the entire space from the tropics to high latitudes. Ice formation in the Pacific Ocean occurs in the Antarctic regions, as well as in the Bering, Okhotsk and Japan Seas (partly in the Yellow Sea, bays of the eastern coast of Kamchatka and O.

Hokkaido and the Gulf of Alaska). The distribution of ice mass across the hemispheres is very uneven. Its main share is in the Antarctic region.

In the north of the ocean, the overwhelming majority of the floating ice formed in winter melts by the end of summer. The fast ice does not reach a significant thickness during the winter and also collapses in the summer.

In the northern part of the ocean, the maximum age of ice is 4-6 months. During this time, it reaches a thickness of 1-1.5 m. The southernmost boundary of floating ice was noted off the coast of about. Hokkaido at 40 ° N. sh., and off the eastern coast of the Gulf of Alaska - at 50 ° N. The middle position of the ice spreading boundary passes over the continental slope.

The southern deep-water part of the Bering Sea never freezes, although it is located much to the north of the freezing regions of the Sea of ​​Japan and the Sea of ​​Okhotsk. The removal of ice from the Arctic Ocean is practically absent. On the contrary, in summer, part of the ice is carried out from the Bering Sea to the Chukchi Sea. In the north of the Gulf of Alaska, several coastal glaciers (Malaspina) are known to produce small icebergs. Usually, ice in the northern part of the ocean is not a major obstacle to ocean shipping.

Only in some years, under the influence of winds and currents, ice "plugs" are created that close the navigable straits (Tatarsky, La Perouse, etc.) In the southern part of the ocean, large masses of ice are present all year round, and all types of it spread far to the north.

Even in summer, the edge of floating ice is kept at an average of about 70 ° S. sh., and in some winters with especially harsh conditions, ice spreads up to 56-60 ° S. sh. of floating sea ice by the end of winter reaches 1.2-1.8 m.

It no longer has time to grow, since it is carried out by currents to the north into warmer waters and collapses. There are no perennial pack ice in Antarctica. The powerful ice sheets of Antarctica give rise to numerous icebergs, which reach 46-50 ° S. NS. Farthest north, they are carried in the eastern part of the Pacific Ocean, where individual icebergs were found almost at 40 ° S.

NS. The average size of Antarctic icebergs is 2-3 km long and 1-1.5 km wide. The record size is 400 × 100 km. The height of the above-water part ranges from 10-15 m to 60-100 m. The main areas of the emergence of icebergs are the Ross and Amundsen Seas with their large ice shelves. The processes of ice formation and melting are an important factor in the hydrological regime of water masses in the high-latitude regions of the Pacific Ocean. Features of atmospheric circulation. over the water area and adjacent parts of the continents, first of all, the general scheme of surface currents in the Pacific Ocean is determined.

Similar and genetically related circulation systems are formed in the atmosphere and ocean. As in the Atlantic, northern and southern subtropical anticyclonic currents and cyclonic circuits in northern temperate latitudes are formed in the Pacific Ocean.

But unlike other oceans, there is a powerful stable Inter-trade countercurrent, which forms with the North and South Trade winds two narrow tropical circuits in the equatorial latitudes: the northern one is cyclonic and the southern one is anticyclonic.

Off the coast of Antarctica, under the influence of winds with an eastern component blowing from the mainland, the Antarctic Current is formed. It interacts with the current of the West Winds, and here another cyclonic circulation is formed, which is especially pronounced in the Ross Sea.

Thus, in the Pacific Ocean, in comparison with other oceans, the dynamic system of surface waters is most pronounced. Zones of convergence and divergence of water masses are associated with circuits. On the western coasts of North and South America in tropical latitudes, where the discharge of surface waters by the California and Peruvian currents is enhanced by steady winds along the coast, upwelling is most pronounced. An important role in the circulation of the Pacific Ocean waters belongs to the subsurface Cromwell Current. , which is a powerful stream moving under the South Tradewind Current at a depth of 50-100 m and more from west to east and compensating for the loss of water driven by the trade winds in the eastern part of the ocean. The length of the current is about 7000 km, the width is about 300 km, the speed is from 1.8 to 3.5 km / h.

The average speed of most of the main surface currents is 1-2 km / h, the Kuroshio and Peruvian currents are up to 3 km / h.

m3 / s (for comparison, the California current is 10-12 million m3 / s). The tides in most of the Pacific Ocean are irregular semidiurnal. In the southern part of the ocean, tides of a regular semi-diurnal character prevail.

Small areas in the equatorial and northern part of the water area have diurnal tides.

130. The organic world of the Pacific. The fauna, numbering in total up to 100 thousand species, is characterized by mammals, living mainly in temperate and high latitudes. The representative of toothed whales, the sperm whale, is widespread, and several species of striped whales are among the toothless whales.

Their fishing is strictly limited. Separate genera of the family of eared seals (sea lions) and fur seals are found in the south and north of the ocean. Northern seals are valuable fur-bearing animals, the fishing of which is strictly controlled. In the northern waters of the Pacific Ocean, there are also very rare sea lions (from eared seals) and a walrus, which has a circumpolar range, but is now on the verge of extinction. The fauna is very rich. fish.

In tropical waters, there are at least 2000 species, in the northwestern seas - about 800 species. The Pacific Ocean accounts for almost half of the world's fish catch.

The main fishing areas are the northern and central parts of the ocean. The main commercial families are salmon, herring, cod, anchovies, etc. The predominant mass of living organisms inhabiting the Pacific Ocean (like other parts of the World Ocean) is invertebrates that live at different levels of ocean waters and at the bottom of shallow waters: these are protozoa, coelenterates, arthropods (crabs, shrimps), molluscs (oysters, squids, octopuses), echinoderms, etc.

They serve as food for mammals, fish, seabirds, but also constitute an essential component of marine fisheries and are objects of aquaculture. The Pacific Ocean, due to the high temperatures of its surface waters in tropical latitudes, is especially rich in various species coral, including those with a calcareous skeleton. None of the oceans has such an abundance and variety of coral structures of various types as in the Pacific. plankton are unicellular representatives of the animal and plant world.

The phytoplankton of the Pacific Ocean contains almost 380 species.

131. Island land of the Pacific Ocean. The Pacific Ocean has a huge number of large and small islands (about 10,000). Clusters of islands, most of which are located between 28.5 ° N. NS. and 52.5 ° S.

NS. - Hawaiian Islands in the north and about. Campbell in the south is often referred to as Oceania. Most of them are concentrated in equatorial and tropical latitudes. Most of them are grouped into archipelagos, but there are also isolated islands. The total area of ​​Oceania is 1.26 mln.

km2, of which 87% of the area is occupied by about. New Guinea and the New Zealand Islands and 13% all the rest. Historically, Oceania has been divided into parts: 1. Melanesia ("Black Island") - the southwest of Oceania, which includes the islands of New Guinea, Bismarck, Solomon, New Hebrides, New Caledonia, Fiji and other smaller islands; 2. Micronesia ("Melkoostrovye") - the islands of the Mariana, Caroline, Marshall, Gilbert and others; 3.

Polynesia ("Multi-island") includes the islands of the central part of the Pacific Ocean, the largest of which are Hawaiian, Marquesas, Tuamotu, Tonga, about. Easter, etc.; 4. The islands of New Zealand - North and South, Sewart and others. The islands of Oceania have been known to Europeans since the era of the great geographical discoveries, when, crossing the ocean, navigators discovered and, to one degree or another, described the nature and population of numerous archipelagos in the Pacific Ocean. However, until the middle of the 18th century. these discoveries were made in the strip of trade winds between the northern and southern tropics, since sailing ships did not enter the south due to strong winds and currents.

J. Cook was the first to pave the way using westerly winds and currents of temperate latitudes. In the years 1768-1779. during three voyages, he explored New Zealand, discovered a number of archipelagos in the south of Oceania and the Hawaiian Islands in the north. Many islands were discovered by Russian sailors on round-the-world voyages and expeditions in search of new lands.

N. N. Miklukho-Maclay's contribution to the study of the population of New Guinea and other islands is widely known.

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The World Ocean is the main part of the hydrosphere, making up 94.2% of its entire area, a continuous, but not continuous, water shell of the Earth, surrounding continents and islands, and characterized by a common salt composition.

Continents and large archipelagos divide the world's oceans into four large parts (oceans):

Atlantic Ocean,

Indian Ocean,

Pacific Ocean,

Arctic Ocean.

Sometimes it also stands out

South ocean.

Large regions of the oceans are known as seas, bays, straits, etc.

n. The doctrine of terrestrial oceans is called oceanology.

Division of the World Ocean.

Main morphological characteristics of the oceans

(according to the "Atlas of the Oceans". 1980)

Oceans Area

surface

water, mln.km² Volume,

million km³ Average

m The greatest

depth of the ocean,

Atlantic 91.66 329.66 3597 Trench Puerto Rico (8742)

Indian 76.17 282.65 3711 Sunda Trench (7209)

Arctic 14.75 18.07 1225 Greenland Sea (5527)

Quiet 178.68 710.36 3976 Mariana Trench (11022)

World 361.26 1340.74 3711 11022

Today, there are several views on the division of the World Ocean, taking into account hydrophysical and climatic features, water characteristics, biological factors, etc.

Already in the 18th-19th centuries, there were several such versions. Malta-Brun, Conrad Malte-Brun and Fleurier, Charles de Fleurier identified two oceans. The division into three parts was proposed, in particular, by Philippe Buache and Heinrich Stenffens.

The Italian geographer Adriano Balbi (1782-1848) identified four regions in the World Ocean: the Atlantic Ocean, the North and South Arctic Seas and the Great Ocean, of which the modern Indian became a part (such a division was a consequence of the impossibility of determining the exact border between the Indian and Pacific Oceans and the similarity of zoogeographic conditions of these regions).

Today, they often talk about the Indo-Pacific region - a zoogeographic zone located in the tropical sphere, which includes the tropical parts of the Indian and Pacific Oceans, as well as the Red Sea. The region's border runs along the coast of Africa to Cape Needles, later from the Yellow Sea to the northern shores of New Zealand, and from Southern California to the Tropic of Capricorn.

In 1953, the International Hydrogeographic Bureau developed a new division of the World Ocean: it was then that the Arctic, Atlantic, Indian and Pacific Oceans were finally allocated.

Geography of the oceans

Average annual surface temperature of the World Ocean

General physical and geographical information:

Average temperature: 5 ° C;

Average pressure: 20 MPa;

Average density: 1.024 g / cm³;

Average depth: 3730 m;

Total weight: 1.4 · 1021 kg;

Total volume: 1370 million km³;

The deepest point in the ocean is the Mariana Trench, located in the Pacific Ocean near the Northern Mariana Islands.

Its maximum depth is 11022 m. It was explored in 1951 by the British submarine Challenger II, in honor of which the deepest part of the depression was named the Challenger Abyss.

The waters of the oceans

The waters of the World Ocean make up the main part of the Earth's hydrosphere - the oceanosphere.

Ocean waters account for more than 96% (1338 million cubic kilometers) of the Earth's water. The volume of fresh water entering the ocean with river runoff and precipitation does not exceed 0.5 million cubic kilometers, which corresponds to a layer of water on the ocean surface with a thickness of about 1.25 m. This determines the constancy of the salt composition of ocean waters and insignificant changes in their density.

The unity of the ocean as a water mass is ensured by its continuous movement in both horizontal and vertical directions. In the ocean, as in the atmosphere, there are no sharp natural boundaries, they are all more or less gradual. Here the global mechanism of energy transformation and metabolism is carried out, which is supported by uneven heating by solar radiation of surface waters and the atmosphere.

Bottom relief

Deviations of the geoid (EGM96) from the idealized figure of the Earth (ellipsoid WGS84).

It can be seen that the surface of the World Ocean is actually not smooth everywhere, for example, in the north of the Indian Ocean it is lowered by ~ 100 meters, and in the west of the Pacific Ocean it is raised by ~ 70 meters.

Main article: Ocean floor

The systematic study of the seabed of the world's oceans began with the advent of the echo sounder. Most of the ocean floors are flat surfaces, the so-called abyssal plains. Their average depth is 5 km. In the central parts of all oceans, there are linear uplifts of 1-2 km - mid-ocean ridges, which are connected into a single network.

The ridges are divided by transform faults into segments that appear in the relief by low elevations perpendicular to the ridges.

On the abyssal plains there are many solitary mountains, some of which protrude above the water surface in the form of islands. Most of these mountains are extinct or active volcanoes. Under the weight of the mountain, the oceanic crust sags and the mountain slowly sinks into the water. A coral reef forms on it, which builds on the summit, as a result of which a ring-shaped coral island is formed - an atoll.

If the edge of the continent is passive, then between it and the ocean there is a shelf - the underwater part of the continent, and a continental slope, smoothly turning into an abyssal plain.

In front of the subduction zones, where the oceanic crust plunges under the continents, there are deep-sea trenches - the deepest parts of the oceans.

Igneous rocks. (No.17)

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Humanity could only study the ocean floor in the second half of the 20th century, when there were devices that could dive to great depths. As expected, it turned out that the topography of the ocean floor, as well as the land, is not flat.

Each ocean has a vast mountain range. In the Pacific Ocean, it is located in the eastern part and in all others - in the middle of the oceans.

Therefore, these mountain ranges are called Mediterranean reefs. The reason for their appearance is the spreading of lithospheric plates and magma, which turns into lava. Hence the reefs.

If you combine the lava, it forms the so-called "black smoker" - cones about 50 m.

Many substances come from the intestines of the Earth, which form minerals containing precious metals.

The height of the ridges exceeds 2 km above the ocean surface. Some of the reef tops rise above sea level.

For example, this is the island of Iceland.

On each side of the middle ocean is an ocean bed. In fact, it is a flat area. From a depth of 3-6 km. The bottom is covered with more than 200 m of precipitation. Il is mineral dust and the remains of marine organisms.

The oceans have volcanoes that look like underwater reefs.

Some are extinct, others are active. Some of the reef reefs are islands.
The so-called transition zone extends from the bed from the oceans to the continental coast. It has different shelves and continental slopes.

The shelf is part of an ocean-filled continent. The depth is not more than 200 m. The width of the shelves in different oceans varies, as on the widest shelf in the Arctic Ocean (1000 km).

The continental slope is a narrow transition between the shelf and the ocean layer.

In the Pacific Ocean, and not on the continental slope, deep-sea ditches stand out, which are long and narrow cavities. The reason for their appearance is the collision of the lithospheric plate. Volcanoes and earthquakes are nothing unusual here.

The deepest trough is the Mariana Trenches, located east of the Japanese and Philippine Islands in the Pacific Ocean. Its maximum depth is over 11 km.

Geography

Grade 7 textbook

Oceans and continents

In this section, you will explore the oceans and continents - the largest parts of the geographic envelope.

Each ocean and continent is a kind of natural complex. They differ in their size, relative position, surface height or depths in the ocean, other natural features, and human economic activity.

Oceans

The oceans embrace the Earth with inseparable waters and are by their nature a single element that acquires different properties with changing latitudes.

Off the coast of Greenland and Antarctica, in the roaring winds of the forties, storms rage all year round. Near the tropics, the Sun bakes mercilessly, trade winds blow and only sometimes destructive hurricanes sweep through. But the huge World Ocean is also divided by continents into separate oceans, each of which has its own special natural features.

§ 17. Pacific Ocean

Pacific Ocean- the largest in area, the deepest and most ancient of the oceans.

Its main features are great depths, frequent movements of the earth's crust, many volcanoes at the bottom, a huge supply of heat in its waters, an exceptional diversity of the organic world.

Geographic location of the ocean. The Pacific Ocean, also called the Great Ocean, occupies 1/3 of the planet's surface and almost 1/2 of the area of ​​the World Ocean.

It is located on both sides of the equator and 180 ° meridian. This ocean separates and simultaneously connects the shores of five continents. The Pacific Ocean is especially wide at the equator, so it is the warmest on the surface.

In the east of the ocean, the coastline is poorly dissected, several peninsulas and bays stand out (see map). In the west, the banks are heavily indented. There are many seas here. Among them there are offshore ones, located on the continental shelf, with depths of no more than 100 m.

Some seas (which ones?) Lie in the zone of interaction of lithospheric plates. They are deep and separated from the ocean by island arcs.

From the history of ocean exploration. Many peoples inhabiting the Pacific shores and islands, for a long time, sailed on the ocean, mastered its riches. The beginning of the penetration of Europeans into the Pacific Ocean coincided with the era of the great geographical discoveries.

F. Magellan's ships crossed the vast expanse of water from east to west in a few months of sailing. All this time, the sea was surprisingly calm, which gave Magellan the reason to call it the Pacific Ocean.

Rice. 41. Sea surf

Much information about the nature of the ocean was obtained during the voyages of J.

Cook. Russian expeditions led by I.F.Kruzenshtern, M.P.

Lazarev, V.M. Golovnin, Yu. F. Lisyansky. In the same XIX century. complex research was carried out by S.O. Makarov on the Vityaz ship. Since 1949, Soviet expeditionary ships have made regular scientific voyages. A special international organization is engaged in the study of the Pacific Ocean.

Features of nature. The topography of the ocean floor is complex.

The continental shelf (shelf) is well developed only off the coasts of Asia and Australia. The continental slopes are steep, often stepped. Large uplifts and ridges divide the ocean floor into hollows. Near America, the East Pacific Rise is located, which is part of the system of mid-ocean ridges.

There are more than 10,000 individual seamounts on the ocean floor, mostly of volcanic origin.

The lithospheric plate, on which the Pacific Ocean lies, interacts with other plates at its borders.

The edges of the Pacific Plate plunge into the tight space of trenches that encircle the ocean in a ring. These movements give rise to earthquakes and volcanic eruptions. Here lies the famous "Ring of Fire" of the planet and the deepest Mariana Trench (11022 m).

The ocean climate is diverse. The Pacific Ocean is located in all climatic zones, except for the north polar one. Above its vast expanses, the air is saturated with moisture. In the equator, up to 2000 mm of precipitation falls. The Pacific is protected from the cold Arctic Ocean by land and underwater ridges, so its northern part is warmer than the southern one.

42. Sea of ​​Japan

The Pacific Ocean is the most turbulent and formidable among the oceans of the planet. Trade winds blow in the central parts of it. In the west, monsoons are developed. In winter, a cold and dry monsoon comes from the mainland, which has a significant impact on the ocean climate; part of the seas is covered with ice.

Often devastating tropical hurricanes - typhoons ("typhoon" means "strong wind") sweep over the western part of the ocean. In temperate latitudes, storms rage throughout the cold half of the year. The western air transport prevails here. The highest waves up to 30 m high were recorded in the north and south of the Pacific Ocean.

Hurricanes raise whole water mountains in it.

The properties of water masses are determined by the characteristics of the climate. Due to the large extent of the ocean from north to south, the average annual water temperature on the surface varies from -1 to + 29 ° С. In general, precipitation in the ocean prevails over evaporation; therefore, the salinity of surface waters in it is somewhat lower than in other oceans.

The currents in the Pacific Ocean are consistent with their general scheme in the World Ocean, which you already know.

Since the Pacific Ocean is strongly elongated from west to east, latitudinal water flows prevail in it. Both in the northern and southern parts of the ocean, ring-shaped movements of surface waters are formed.

(Trace their directions on the map, name the warm and cold currents.)

The organic world of the Pacific is distinguished by an extraordinary richness and diversity of plant and animal species. It is home to half of the entire mass of living organisms in the World Ocean. This feature of the ocean is explained by its size, variety of natural conditions and age. Life is especially rich in tropical and equatorial latitudes near coral reefs.

There are many salmon fish in the northern part of the ocean. In the southeast of the ocean, off the coast of South America, huge concentrations of fish are formed. The water masses here are very fertile, they develop a lot of plant and animal plankton, which feed on anchovies (herring fish up to 16 cm long), horse mackerel, mackerel and other fish species.

Birds eat a lot of fish here: cormorants, pelicans, penguins.

The ocean is inhabited by whales, seals, sea beavers (these pinnipeds live only in the Pacific Ocean). There are also many invertebrates - corals, sea urchins, molluscs (octopuses, squids). It is home to the largest mollusk - tridacna, weighing up to 250 kg.

The Pacific Ocean has all natural belts, except for the north polar one.

Each of them has its own characteristics. The northern subpolar belt occupies a small part of the Bering and Okhotsk seas. The temperature of the water masses is low here (down to -1 ° C).

In these seas, there is an active mixing of waters, and therefore they are rich in fish (pollock, flounder, herring). There are many salmon and crabs in the Sea of ​​Okhotsk.

Vast territories are covered by the northern temperate belt. It is strongly influenced by westerly winds, and storms are frequent here. In the west of this belt lies the Sea of ​​Japan - one of the richest in a variety of species of organisms.

In the equatorial zone, at the boundaries of currents, where the rise of deep waters to the surface increases and their biological productivity increases, many fish live (sharks, tuna, sailboats, etc.).

In the southern tropical zone of the Pacific Ocean off the coast of Australia there is a unique natural complex of the Great Barrier Reef.

This is the largest “mountain range” on Earth, created by living organisms. It is comparable in size to the Ural ridge. Under the protection of islands and reefs in warm waters, coral colonies develop in the form of bushes and trees, columns, castles, bouquets of flowers, mushrooms; corals are light green, yellow, red, blue, purple. Many mollusks, echinoderms, crustaceans, and various fish also live here. (Describe other belts on the atlas map.)

Economic activities in the ocean. More than 50 coastal countries are located on the shores and islands of the Pacific Ocean, in which about half of humanity lives.

(Which countries are these?)

Rice. 43. The relief of the Pacific Ocean floor. What are the structural features of the bottom relief?

The use of the natural resources of the ocean began in antiquity.

Several centers of navigation arose here - in China, Oceania, South America, and the Aleutian Islands.

The Pacific Ocean plays an important role in the lives of many peoples. Half of the world's fish catch comes from this ocean (see Figure 26). In addition to fish, a part of the catch is made up of various mollusks, crabs, shrimps, and krill.

In Japan, algae and molluscs are grown on the seabed. In some countries, salt and other chemicals are extracted from sea water and desalinated.

On the shelf, metal placers are being developed. Oil is mined off the coast of California and Australia. Ferromanganese ores were found on the ocean floor.

Important sea routes pass through the greatest ocean of our planet, the length of these routes is very long.

Navigation is well developed, mainly along the coasts of the continents. (Find Pacific ports on the map.)

Human economic activity in the Pacific Ocean has led to the pollution of its waters, to the depletion of some types of biological resources.

So, by the end of the 18th century. mammals were exterminated - sea cows (a species of pinnipeds), discovered by one of the members of the expedition V. Bering. On the verge of extermination at the beginning of the XX century. there were seals, the number of whales decreased.

Currently, their fishing is limited. A great danger in the ocean is posed by water pollution by oil, some heavy metals and wastes from the nuclear industry. Harmful substances are carried by currents throughout the ocean. Even off the coast of Antarctica, these substances were found in the composition of marine organisms.

1. Highlight the most characteristic features of the Pacific Ocean nature.
2. What are the types of economic activities in the ocean? Indicate fishing and other fishing areas.
3. What is the negative human impact on the nature of the Pacific Ocean?
4. Plot the route of a cruise ship or research ship on the map. Explain the directions of the routes by the purpose of the voyage.

The relief of the shelf of the underwater margins of the continents.

About 35% of the continental area is covered by the waters of the seas and oceans. The mega-relief of the underwater continental margin has its own essential features. About 2/3 of it falls on the northern hemisphere and only 1/3 - on the southern. We also note that the larger the ocean, the smaller part of its area is occupied by the underwater margin of the continents.

For example, in the Pacific Ocean it is 10%, in the Arctic Ocean - more than 60%. The submarine margin of the continents is divided into a shelf, a continental slope and a continental foot.

Shelf. The coastal, relatively shallow-water part of the seabed with a more or less leveled relief, structurally and geologically representing a direct continuation of the adjacent land, is called a shelf.

About 90% of the shelf area is made up of flooded plains of continental platforms, which in different geological epochs, due to changes in ocean level and vertical movements of the earth's crust, were flooded to a greater or lesser extent.

For example, in the Cretaceous, shelves were much more widespread than they are now. During the Quaternary glaciations, the ocean level dropped by more than 100 m in comparison with the modern one, and, accordingly, the vast expanses of the present shelf were then continental plains.

Thus, the upper boundary of the shelf is not constant; it changes due to absolute and relative fluctuations in the level of the World Ocean. The most recent level changes have been associated with the alternation of glacial and interglacial eras in the Quaternary. After the ice sheet melted in the northern hemisphere, the ocean level rose by about 100 m compared to its position during the last glaciation.

The relief of the shelf is predominantly flat: the average slopes of the surface are from 30 ′ to G.

Within the limits of the shelf, relic relief forms are widespread, which appeared in the past in continental conditions (Fig. 25). For example, on the US Atlantic shelf north of Cape Cod, the bottom is a flooded ice-accumulative plain with

characteristic forms of glacial relief. South of Cape Cod Peninsula

the last glaciation did not spread, there is a hilly plain with rounded "soft" watersheds and clearly expressed flooded river valleys.

In many areas within the shelf, various structural denudation (also relict) landforms are widespread, formed as a result of the impact of denudation processes on geological structures. Thus, with monoclinal bedding of rocks, a characteristic ridge relief is quite often formed associated with the preparation of solid rocks.1 Along with relict subaerial plains, abrasion plains, developed either in the past or at present sea level (benny of the coastal zone), as well as accumulative plains are found on the shelf. composed of modern marine sediments.

Since the shelf plains are predominantly submerged plains of the continental platforms, the large relief features here are determined (as well as on land) by the structural features of these platforms. The lowered areas of the shelf often correspond to syneclises, uplands - to anteclises.

On the shelf, there are often separate depressions, which are deepened relative to the adjacent sections of the bottom. In most cases, these are grabens, the bottoms of which are lined with a layer of modern marine sediments. Such, for example, are the Kandalaksha depression of the White Sea, the depth of which is more than 100 m higher than the depth of neighboring areas, the St. Lawrence Trench on the Canadian shelf of the Atlantic Ocean, etc.

Previously, it was believed that the shelf ends at a depth of 200 m, where it gives way to a continental slope.

Modern research has shown that it is difficult to talk about any specific depth to which the shelf extends. The boundary between the shelf and the continental slope is morphological. This is the edge of the shelf - almost always a clearly pronounced bend in the bottom profile, below which its slopes increase significantly. Often, the edge is at a depth of 100-130 m, sometimes (for example, on modern abrasive underwater plains) it is noted at depths

50-60 and 200 m.

There are also shelf plains that extend to much greater depths. So, most of the bottom of the Sea of ​​Okhotsk is a shelf in terms of geological and geomorphological features, and the depths here are mainly 500-600 m, in some places they reach 1000 m and more.

In the typically shelf Barents Sea, the shelf edge runs at a depth of more than 400 m.This suggests that the origin of the shelf is associated not only with the flooding of the marginal land plains as a result of sea level rise, but also with the latest tectonic subsidence of the continental margins.

One of the interesting forms of the shelf relief is the submerged coastlines - complexes of coastal abrasion and accumulative forms that mark sea levels in past eras.

The study of ancient coastlines, as well as the study of shelf deposits, makes it possible to find out specific details of the history of shelf development in a particular area.

Various forms are also widespread on the shelf.

topography formed by modern subaqueous processes - waves, tidal currents, etc. (see Ch. 19).

In tropical waters within the shelf, coral reefs are typical - landforms created by colonies of coral polyps and calcareous algae (see Chapter 20).

Coastal seabeds adjacent to transition zone islands or oceanic islands, flattened and relatively shallow, are also commonly referred to as the shelf.

This type of shelf covers an insignificant area, accounting for only a few percent of the entire shelf area, which is mainly of platform structure.

Continental (continental) slope.

A more or less narrow seabed zone below (deeper) the shelf edge, characterized by a relatively steep surface slope, is a continental slope. The average slope of the continental slope is 5-7 °, often 15-20 °, sometimes even more than 50 °.

The continental slope often has a stepped profile, and steep slopes

fall just on the ledges between the steps. The bottom between the ledges looks like an inclined plain. Sometimes the steps are very wide (tens and hundreds of kilometers).

They are called the marginal plateaus of the continental slope. A typical example of a fringe plateau is the Blake Submarine Plateau east of Florida (Figure 26). It is separated from the shelf at depths of 100-500 m by a ledge and further extends in the form of a wide

an inclined step to the east to a depth of 1500 m, where it ends with a very steep scarp, going to a great depth (more than 5 km). On the mainland slope of Argentina, there are up to a dozen of these (but more

narrow) steps.

Submarine canyons dissecting it across the strike are widespread within the continental slope. These deep

incised hollows are sometimes located so that they give the edge of the

shelf fringe look.

The incision depth of many canyons reaches 2000 m, and the length of the largest of them is hundreds of kilometers. The slopes of the canyons are steep, the transverse profile is often V-shaped. Slopes

the longitudinal profile of underwater canyons in the upper reaches on average 0.12, in the middle sections - 0.07, in the lower - 0.04. Many canyons have branches, there are winding canyons, more often rectilinear. They cut through the entire continental slope, and the largest can be traced in the area of ​​the continental foot. At the mouths of the canyons, large accumulative forms are usually noted - fan cones.

The underwater canyons are reminiscent of river valleys or canyons of mountainous countries.

It is characteristic that many large canyons lie opposite the mouths of large rivers, forming, as it were, underwater extensions of their valleys. These similarities and connections between submarine canyons and river valleys gave rise to the idea that submarine canyons are not submerged river valleys.

This is how the erosional, or fluvial, hypothesis of the formation of underwater

canyons.

However, with certain similarities, there are also noticeable differences between underwater canyons and river valleys. The longitudinal profile of most canyons is much steeper than

zones of rock crushing.

A large, if not the main, role in the formation of the morphological appearance of underwater canyons belongs to the activity of turbidity flows, which will be discussed below (see Chapter 20).

The continental slope is characterized by a continental type of crust. Samples of bedrocks taken in underwater canyons and on the steps of the continental slope from research vessels using special instruments - dredges, showed that these are rocks of the same composition and age as on the adjacent land and on the shelf.

Most convincingly geological and

the geomorphological unity of the continental platforms of land, shelf and continental slope has been proven by underwater drilling and geophysical data.

Thus, the geological profile constructed from offshore wells and geophysical data in the Blake Plateau area indicates that the geological strata that make up the coastal plain of Florida can be traced both within the shelf and on the edge of the Blake Plateau.

Many areas of the continental slope (for example, in the Gulf of Mexico, in the Mediterranean Sea) are characterized by hilly relief forms due to salt tectonics.

Sometimes there are also volcanic and mud volcanic formations. Continental foot. The continental foot, along with the shelf and the continental slope, is the largest relief form on the continental margin. In the relief of the bottom of the seas and oceans, the continental foot in most cases is expressed by an inclined plain adjacent to the base of the continental slope and

stretching strip several hundred kilometers wide between

continental slope and ocean floor.

The maximum slope of the plain up to 2.5 ° is located near the base of the continental slope. Towards the ocean, it gradually flattens and ends at depths of the order of 3.5-4.5 km. The surface of the plain when crossing it along the strike, i.e.

along the base of the continental slope, slightly undulating. In places it is cut

large underwater canyons. A significant part of the surface of the plain is formed by fan cones located at the mouths of large submarine canyons.

In the upper part of the transverse profile of the continental foot, a characteristic hilly-depression relief is often noted, strongly resembling a landslide land relief, only represented by larger forms.

In general, the continental foot in typical expression is predominantly accumulative formation. As evidenced by the data of geophysical studies, the cover of marine sediments on the ocean floor reaches its maximum thickness precisely at the continental foot. If on average in the ocean the thickness of loose sediments rarely exceeds 200-500 m, then at the continental foot it can reach 10-15 km.

With the help of deep seismic sounding, it was found that the structure of the continental foot is characterized by a deep deflection of the earth's crust, and a large thickness of sediments here arises precisely as a result of filling this depression.

The main source of sedimentary material input is the products of destruction of land rocks carried by rivers to the shelf, from where this material is carried out in huge quantities as a result of underwater slumping of sediment masses and the action of turbidity flows (for more details, see.

ch. twenty). Underwater canyons serve as trails for the most

powerful turbidity flows, which create huge fan cones in the mouths of underwater canyons. Thus, the entire accumulative plain of the continental foot can be regarded as a huge plume of sediments accumulating at the base of the continental slope.

Under the thick stratum of sediments, a continental-type crust still continues, although its thickness here noticeably decreases. In some cases, the stratum that composes the continental foot lies on the oceanic crust due to its extension beyond the development of the continental crust.

More often, a granite layer is found in the earth's crust, which composes the continental foot, which makes it possible to consider it, along with the shelf and the continental slope, one of the major elements of the underwater margin of the continent. In some areas, the structure of the continental foot is markedly different from that described above. For example, to the east of the already mentioned Blake Plateau, the continental foot in the relief of the ocean floor is expressed by a very deep depression (up to 5.5 km deep), adjacent in the form of a narrow strip to the foot of the plateau.

Apparently, this is a structural trough, typical of the deep structure of the continental foot, but not yet filled with sediments.

In the western part of the Mediterranean Sea, the continental foot is expressed by a hilly relief due to the development of salt-domed structures. The widespread development of such continental margins is confined to passive continental margins

(to the outskirts of the Atlantic type).

Borderlands and micro-continents.

In some areas, the underwater margin of the continent is so fragmented by ruptured tectonic faults that it is practically impossible to distinguish such elements as a shelf, a continental slope, or a continental foot. So, off the coast of California, the transition from the mainland to the ocean is represented by a wide strip of bottom with a very rugged relief. Large hills with flat tops and steep slopes alternate with similar in size and

outlines with depressions.

This relief arose as a result of the manifestation

intensive tectonic processes, which led to the fragmentation of the submarine margin of the continent into a number of horsts and grabens. Such fragmented areas of the underwater outskirts of the continents are called the borderland. They are confined to the tectonically active margins of the continents (margins of the Pacific type).

Within the oceans, there are sometimes underwater or above-water heights composed of continental crust, but not connected with the continents.

They are separated from the continents by vast expanses of the bottom with an oceanic type of the earth's crust. Such are, for example, the Seychelles and their underwater base - the Seychelles Bank (western part of the Indian Ocean). Even larger formations of this kind are the underwater margins of New Zealand, which together with it form an array

continental crust with an area of ​​more than 4 million km2.

Flat-topped uplifts Zenith, Naturalist and others in

The Western Australian Indian Ocean Basin is also composed of continental crust.

Such forms are often considered as residues of more

vast once continental platforms, now plunged to the bottom of the ocean. In principle, the opposite assumption is also possible: perhaps these are areas where the process of formation of the continental crust began, but for some reason did not receive further development.

Such heights, made up of the continental crust, but surrounded on all sides by oceanic crust, are called microcontinents.

The relief of the bottom of the World Ocean is of interest to many researchers, given that this aspect is still not fully understood. In any case, there are mysteries and phenomena that are inexplicable from the point of view of science, which are hidden in the Pacific Ocean. The relief of the bottom of this part of the World Ocean is of great interest to scientists all over the world, therefore, studies of a similar topic are arranged with enviable frequency. It was scientific expeditions studying the bottom of the Pacific Ocean that received results that at one time completely changed the human idea not only about the bottom itself, but also about the geological in general.

Oceanic platforms

The features of the relief of the Pacific Ocean floor surprise many researchers. But speaking in order, it is worth starting with the concept of "oceanic platforms".

They represent certain areas of the cortex that have long since lost their mobility, as well as the ability to deform. Scientists also distinguish those areas of the ocean floor that are still quite active at the present time - geosynclines. Such active areas of the crust are widespread in the Pacific Ocean, namely in its western part.

Ring of Fire

What is the so-called "ring of fire"? In fact, it is located in its very center, and it is in this that it differs significantly from its relatives. For your information, about 600 volcanoes are currently recorded on land, but 418 of them are located on the shores of the Pacific Ocean.

There are volcanoes that do not stop their violent activity even in our time. This concerns, first of all, the famous Fuji, and there are also volcanoes that remain visibly calm for a fairly long period, but at one point they can suddenly turn into fire-breathing monsters. For example, it is said about such a volcano as Bandai-san in Japan. Several villages were affected as a result of his awakening.

Scientists have even registered a volcano at the bottom of the Pacific Ocean.

Awakened volcanoes of the "ring of fire"

In addition to the famous and world-famous awakened Bandai-San volcano, many more similar cases have been recorded. For example, located in one of the districts of Kamchatka, in the 1950s, it declared itself to the whole world. When he woke up from centuries of sleep, seismologists could register about 150-200 earthquakes a day.

Its eruption shocked many researchers, some of them later could confidently declare that it was one of the most violent volcanic paroxysms of the last century. The only thing that pleases is the absence of settlements and people in the area of ​​the eruption.

And here is another "monster" - the Ruiz volcano in Colombia. His awakening killed more than 20 thousand people.

Hawaiian Islands

In fact, what we see is just the tip of the iceberg that hides the Pacific Ocean. Features of its relief consist mainly in the fact that a rather long chain of volcanoes stretches in the center. And they are precisely the top of the underwater Hawaiian Ridge, which is considered a large volcanic cluster with a length of more than 2000 kilometers.

The Hawaiian Ridge stretches all the way to the Midway Atolls, as well as the Kure Atolls, which are located in the northwest.

Hawaii itself is made up of five active closed volcanoes, some of which can exceed four kilometers in height. This applies primarily to the volcanoes of Mauna Kea, as well as Mauna Loa. The most interesting thing is that if you measure the height of the Maun Loa volcano from the very bottom, which is located at the bottom of the ocean, it turns out that its height is more than ten kilometers.

Trench of the pacific

The most entertaining ocean, and also hiding many secrets, is the Pacific Ocean. The bottom relief surprises with its diversity and is a ground for thought for many scientists.

To a greater extent, this applies to the Pacific Ocean basin, which has a depth of up to 4300 meters, while such formations are the most remarkable element for scientific research. The most famous around the world are Challenger, Galatea, Emden, Cape Johnson, Planeta, Snellius, Tuscarora, Ramalo. For example, Challenger has a depth of 11 thousand 33 meters, followed by Galatea with its depth of 10 thousand 539 meters. Emden is 10,399 meters deep, while Cape Johnson is 10,497 meters deep. The most "shallow" is the Tuscarora depression with its maximum depth along its entire length of 8,513 meters.

Seamounts

If you are ever asked: "Describe the relief of the bottom of the Pacific Ocean," - then you can immediately start talking about seamounts, because this is something that will immediately interest your interlocutor. At the bottom of this wonderful ocean, there are many seamounts called "guyots". They are characterized by their flat tops, and at the same time they can be at a depth of approximately 1.5 kilometers, and then, perhaps, much deeper.

The main theory of scientists is that seamounts were previously active volcanoes that rose above sea level. Later they were washed out and found themselves under water. By the way, the latter fact alarms the researchers, because it may also testify to the fact that earlier this part of the crust experienced a kind of "bending".

Pacific bed

Earlier, many studies were carried out in this direction, a lot of scientific expeditions were sent in order to better examine the bottom of the Pacific Ocean. Photos indicate that the predominant bed of this amazing ocean is made of red clay. To a lesser extent, blue silt or crushed coral fragments can be found at the bottom.

It is noteworthy that large areas of the bottom of the Pacific Ocean are often also covered with diatom, globigerin, radiolarian, and pteropod silt. Another interesting fact is that in various bottom sediments one can quite often find shark teeth or manganese nodules.

General data on the Pacific Ocean floor

The formation of the Pacific Ocean floor is influenced by factors such as exogenous as well as endogenous. The latter are internal and tectonic - they are manifested in the form of various underwater earthquakes, slow movement of the earth's crust, and this is what makes the Pacific Ocean interesting. The bottom topography is constantly changing due to the presence of a huge number of volcanoes both on its coast and deep under water. Exogenous factors include various currents, sea roughness, and turbidity flows. Such streams are characterized by the fact that they are saturated with solid particles that do not dissolve in water, which at the same time move with great speed along the slope. It also significantly changes the bottom topography and the life of marine organisms.

Many scientists were greatly interested in the Pacific Ocean. The bottom relief was conventionally divided into several forms. Namely: the underwater margin of the continents, the transition zone, the ocean floor, as well as the mid-ocean ridges. Of 73 million sq. km 10% of the underwater margin is in the Pacific Ocean.

The continental slope is a part of the bottom, which has a slope of 3 or 6 degrees, and it is also located at the outer edge of the shelf of the underwater margin. It is noteworthy that off the coast of volcanic or coral islands, which are rich in the Pacific Ocean, the slope can reach 40 or 50 degrees.

The transition zone is characterized by the presence of secondary forms, which will be arranged in a strict order. Namely, at first the basin adjoins the continental foot, and from the side of the ocean it will be limited by the steep slopes of the mountain ranges. This is quite typical for the Japanese, East China, Mariana, Aleutian transition zones, which are located in the western part of the Pacific Ocean.

1.2 BOTTOM RELIEF

The Pacific Ocean has a difficult bottom topography. A small part is occupied by the shelf. Its width, near North and South America, is about several tens of kilometers, and off the coast of Eurasia, the shelf spreads over hundreds of kilometers. Deep-sea depressions are located in remote parts of the ocean.

The Pacific Ocean contains the largest number of deep-water pits in the World Ocean. The largest depression on Earth is located here and is called the Mariana Trench (the lowest point lies at a depth of 11,022 m.). There are many hollows in the center of the ocean. In the southeast, the East Pacific Rise is located, which is part of the system of mid-ocean ridges.

Basically, the ocean lies on the Pacific lithospheric plate, which interacts with neighboring plates. In the interaction zones themselves, there are deep-sea depressions and volcanic islands.

The Pacific "Ring of Fire" is formed by a system of deep-sea depressions and mountains located on the continents and islands. All this constitutes a chain of volcanoes that are still active today. Tsunamis constantly occur in the ring, as ground and underwater earthquakes often occur.

1.3 ANIMAL WORLD

The fauna of the ocean is rich and varied. 50% of all animals in the oceans are found here. ...

The Pacific Ocean is the best place to study the structure and patterns of distribution of organisms in the ocean. It is characterized by different climatic conditions, which creates a variety of conditions for the development of life.

Most of the biomass inhabiting the Pacific Ocean is invertebrates living in different levels of ocean waters. For example: protozoa, arthropods (shrimp, crabs), echinoderms, molluscs (squid, octopus, molluscs), coelenterates, etc. They are food for fish, birds, mammals, and they are also an essential part of marine prey. Plankton is an object of Aqua culture.

The Pacific Ocean is home to approximately 100 thousand species of animals, of which 3800 are fish species. Due to the study of many depths of the ocean, scientists were able to find and describe 200 species of animals that live at depths of over 7000 m, including 20 species living over 10,000 m.

The peculiarity of the organic world of the Pacific Ocean is that there are ancient species of animals. Mostly endemism and gigantism. For example: ancient sea urchins, some ancient fish, primitive horseshoe crabs, they have not been found in other oceans. 95% of salmon species live in the Pacific Ocean. Representatives of an endemic form among mammals, such as beaver, sea lion, and fur seal, also live here. The largest bivalve mollusk, tridacna weighing up to 300 kg, lives in the equatorial zone.

In recent years, microorganisms have been discovered that live at temperatures of 250 ° C.

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Nature and ecology of the Pacific

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