Peculiarities of the geographical position of the Pacific Ocean seas. The geographical position of the Pacific Ocean: description and features. Mineral resources of the bottom

The Pacific Ocean stretches over a huge area and is the deepest. It washes almost all continents of the globe with the exception of Africa.

In addition, it has great historical and economic importance.

This topic is studied at school in geography lessons in grade 7 or earlier and is always found in exam tests. Therefore, let us once again recall all the main things that characterize the Pacific Ocean.

Research history

It is believed that the Pacific Ocean was discovered by the conqueror Nunez de Balboa, who first saw the coast. The first travels on the waters were carried out by rafts and canoes. Researchers on the Kon-Tiki raft even managed to cross waters that were still unknown.

It is interesting to know why the Pacific Ocean was called the Pacific. While sailing on its waters, Fernand Magellan did not experience a single storm in a little less than 4 months, the entire time of the trip the water surface was absolutely calm.

In honor of this, the name appeared, translated into English as Pacific ocean.

Characteristics of the largest ocean

The area of \u200b\u200bthe Pacific Ocean is 178.68 million km², it includes 28 seas, including the Yellow, Bering, and Okhotsk.

Surprisingly, it occupies almost half of the area of \u200b\u200bthe entire World Ocean (49.5%), exceeds half the volume of all water on Earth by 3%, which is why it is deservedly considered the largest.

In the Pacific Ocean, the Mariana Trench is located, in which there is the maximum depth among the known ones - 11022 m.The average depth is 3984 m.

Salinity in the middle zone varies from 34 to 36%, while in the north it can reach 1%.

Geographical position

The Pacific Ocean occupies 1/3 of the Earth. From the east, it washes South and North America (their western coasts), from the west it touches the eastern coasts of Eurasia, Australia and Antarctica.

The border with the Arctic Ocean is determined only by the Bering Strait, which runs between the shores of Eurasia and North America.

Currents

There are 7 cold currents in the Pacific Ocean, the main ones are: the South Passat Current, the North Pacific Current, the Cromwell Current, the Alaska and the Inter-trade Countercurrent. There are only 3 warm ones: Californian, Peruvian and westerly winds.

Pacific currents

In the region of Eurasia, monsoons blow on coastal areas, especially in summer. At the equator, the trade winds actively influence the sea current.

In the west of the equator, a large amount of precipitation falls, an average of 1500-2500 mm. In the east, precipitation is extremely rare and insignificant.

Seas

The area of \u200b\u200bthe constituent seas is almost 20% of the total.

Bering Sea

It includes 27 seas, most of which are located along the shores of Eurasia.

Coral sea

The greatest historical and economic significance are: Beringovo, Koralovoye, Yaponskoye, Okhotskoye, Tasmanovo and Philippines.

Climate and climatic zones

Due to its large area, the Pacific Ocean is located in all climatic zones. At the equator, the temperature can reach 24 0 С, while at the coast of Antarctica it drops to 0 and deforms into ice.

In the southern hemisphere, trade winds are strongly influenced - winds that, in given climatic conditions, cause a huge number of typhoons and tsunamis.

Inhabitants of the Pacific

There are about 4,000 fish species in the Pacific Ocean.

The list below summarizes the most famous and abundant species there:

It is believed that the largest ocean has the richest aquatic flora and fauna. This was influenced not only by its length through all climatic zones, but by the varied bottom topography and favorable temperature.

Islands and peninsulas

Most of the islands were formed by volcanic eruptions and tectonic plate shears.

New Guinea islands

In total, there are more than ten thousand islands on the territory of ocean waters, among which the second in area is about. New Guinea - 829,000 km ², in third place about. Kalimantan - 736,000 km², the largest group of islands - the Great Sunda Islands - is also located here.

Solomon islands

Of the most famous islands there are: Kuril, Philippine, Solomon, Galapagos.

California Peninsula

Among the singles, Sakhalin, Taiwan, Sumatra can be distinguished. California, Alaska, Kamchatka and Indochina are peninsulas that wash the waters of the Pacific Ocean.

Bays

The ocean has only 3 large bays, 2 are located in the north (Shelikhova, Alaska).

Shelikhov Bay - the Sea of \u200b\u200bOkhotsk Bay between the Asian coast and the base of the Kamchatka Peninsula

Shelikhov Bay is part of the Sea of \u200b\u200bOkhotsk; several large ports are located in the Gulf of Alaska.

Gulf of california

The Gulf of California is washed by the coast of the California Peninsula, and there are 2 large islands in it.

Features of nature

The main natural features and characteristics of the ocean are its size and depth.

The Pacific Ring of Fire is one of the most active seismic zones in the earth's crust. She got the name of the ring due to the fact that a long chain of volcanoes stretched along the entire coast of the Pacific Ocean.

An exceptionally rare natural phenomenon is located in its waters - the Fireball. Huge reserves of heat are hidden in the depths, thanks to which the richest flora and fauna appeared.

Bottom relief

There are many volcanoes of various sizes on the ocean floor, some of which are still active. Also there you can find underwater basins (sometimes quite large), which are also called pools, since they resemble them in structure.

The relief of the Pacific Ocean floor

Another characteristic feature of the bottom relief can be called depressions, sometimes reaching several tens of meters in depth. At a much greater depth, flat seamounts are found in abundance.

The bottom relief is also distinguished by the fact that it is subject to constant changes due to the shift of tectonic plates and the eruption of underwater volcanoes.

Coastline

The coastline is poorly indented, it includes only 3 large bays and several peninsulas.

Most of the coastline on the North and South American side is flat, but inconvenient for navigation. Mountain ranges occupy a significant part of the coast, while there are very few naturally formed bays and harbors.

Minerals

In the bowels of the ocean, according to scientists, there is about 1/3 of the world's oil reserves, in fact, that is why there is active production there, as well as gas.

The shelves are rich in various minerals, ore, copper and nickel sources (reserves are approximately equal to several billion tons). An abundant source of natural gases has recently been found and is already being mined.

The most curious of them:

Environmental problems of the Pacific

For many years, man has spent the richest resources of the Pacific Ocean, which has led to their significant impoverishment.

And numerous trade routes and mining has affected the environment and caused severe water pollution, which also had a detrimental effect on flora and fauna.

Economic value

More than half of the world's catch comes from the bowels of the Pacific Ocean. Not surprisingly, most of the transport routes also run through the territory of its waters.

Transport routes carry out not only the transportation of passengers, but also the transportation of minerals, resources (industrial, food).

Conclusion

The Pacific Ocean is a huge source of natural resources. It plays an important role in the global economy and ecology of the Earth. However, overuse of its resources can lead to depletion of natural resources and pollution of the largest water basin on Earth.

Geographical location Describe the Pacific Ocean SOE plan :. 1. The area of \u200b\u200bthe ocean and its place among other oceans. 2. The location of the ocean relative to the equator, the tropics (polar circles), the zero and 180th meridians. 3. Extreme points of the ocean, coordinates. Extension in degrees and kilometers from north to south and from west to east. 4. What continents is washed by the ocean. 5. Location in the hemispheres and climatic zones. 6. Oceans, seas, which are part of the ocean 7. Location relative to continents and other oceans. 8. Ocean currents.

SIZE Area with seas 178.620 million km², volume 710 million km³, average depth 3980 m, maximum m. The Pacific Ocean occupies half of the entire water surface of the Earth, and more than thirty percent of the planet's surface area.

Name Its original name is "Great", and it was given by the Spaniard Vasco Nunez de Balboa, who, exploring the New World, on September 30, 1513, crossed the Isthmus of Panama from north to south. Magellan discovered the Pacific Ocean in the fall of 1520 and named the ocean the Pacific Ocean, "because, as one of the participants reports, during the transition from Tierra del Fuego to the Philippine Islands, for more than three months we never experienced the slightest storm." Vasco Nunez de Balboa 30 September 1513 Magellan F. Magellan Vasco Nunez de Balboa

Sea composition: Bering, Okhotsk, Japanese, East China, Yellow, South China, Javan, Sulawesi, Sulu, Philippine, Coral, Fiji, Tasmanovo, etc. The Amundsen, Bellingshausen, Ross Seas are now included in the Southern Ocean. In terms of the number (about 10 thousand) and the total area of \u200b\u200bthe islands (about 3.6 million km²), the Pacific Ocean ranks first among the oceans. In the northern part of the Aleutian; in the western Kuril Islands, Sakhalin, Japanese, Philippine, Large and Small Sunda, New Guinea, New Zealand, Tasmania; in the central and southern parts there are numerous small islands. Mark the islands and seas of the Pacific Ocean on the map. BeringHuntingJapanese

Bottom topography The bottom topography is various. In the east there is the East Pacific uplift, in the central part there are many depressions (North-East, North-West, Central, East, South, etc.), deep-water trenches: in the north Aleutian, Kuril-Kamchatka, Izu-Boninsky; East-Pacific uplift in the west, the Mariana (with the maximum depth of the Marian World Ocean m), Philippine, etc .; in the east, Central American, Peruvian and others.

Currents Main surface currents: warm Kuroshio, North Pacific and Alaskan and cold California and Kuril currents in the northern part of the Pacific Ocean; in the southern part there are warm South Trade winds and East Australian winds and cold West Winds and Peruvian ones. The surface water temperature at the equator ranges from 26 to 29 ° C, in the polar regions up to 0.5 ° C. Salinity 30-36.5 equator Salinity Mark the currents of the Pacific Ocean on a contour map.

Economic importance The Pacific Ocean accounts for about half of the world's fish catch (pollock, herring, salmon, cod, sea bass, etc.). Fishing for crabs, shrimps, oysters, mintai, herring, salmon, sea bass, crabs, shrimp and oysters Important sea and air communications between the countries of the Pacific Basin and transit routes between the countries of the Atlantic and Indian oceans run across the Pacific Ocean. Major ports: Vladivostok, Nakhodka (Russia), Shanghai (China), Singapore (Singapore), Sydney (Australia), Vancouver (Canada), Los Angeles, Long Beach (USA), Huasco (Chile). AtlanticIndian OceansPortsVladivostokNakhodkaRussiaShanghaiChinaSingapurLanguage -BichUSA HuascoChile The date change line passes through the Pacific Ocean along the 180 meridian.

Date line The date line runs here, between the Diomede Islands - Krusenstern Island (USA) (left) lives "yesterday", and Ratmanov Island (Russia) (right) - "today" by the Diomede Islands

The degree of ruggedness of the Pacific Ocean coastline is characterized by ... a. strong dissection in the west and east b. strong dissection in the west and weak in the east c. weak dissection in the west and strong in the east of the city weak dissection in the west and east

Geographical position

Describe GP Pacific as planned: .

1. The area of \u200b\u200bthe ocean and its place among other oceans.

2. The location of the ocean relative to the equator, the tropics (polar circles), the zero and 180th meridians.

3. Extreme points of the ocean, coordinates. Extension in degrees and kilometers from north to south and from west to east.

4. What continents is washed by the ocean.

5. Location in the hemispheres and climatic zones.

6 oceans, seas that make up the ocean

7. Location relative to continents and other oceans.

8. Ocean currents.

THE SIZE Area with seas 178.620 million km², volume 710 million km³, average depth 3980 m , maximum 11022 m ... The Pacific Ocean covers half of the entire water surface of the Earth, and more than thirty percent of the planet's surface area.

NameIts original name was "Great", and it was given by the Spaniard Vasco Nunez de Balboa who, exploring the New World, September 30th 1513 g. crossed the Isthmus of Panama from north to south. Magellan discovered the Pacific Ocean in the fall of 1520 and called the ocean the Pacific Ocean, "because, - as one of the participants reports, during the transition from Tierra del Fuego to the Philippine Islands, more than three months - we have never experienced the slightest storm."

In 1534, on the instructions of the Spanish king Carlos V, the discoverer of the Pacific Ocean, the Castilian hidalgo Don Vasco Nunez de Balboa, made the first topographic surveys to build a canal through the Panama

Map - path Vasco Nunez Balboa, Central America, 1513.

Composition of the Sea: Beringovo , Okhotsk , Japanese , East China , Yellow , South China , Javanskoe , Sulawesi , Sulu , Filipino , Coral , Fiji , Tasmanovo and other Seas Amundsen , Bellingshausen , Ross are now included in South ocean ... By the number (about 10 thousand) and the total area of \u200b\u200bthe islands (about 3.6 million km²), the Pacific Ocean is among oceans first place. In the northern part - Aleutian ; in the west - Kuril , Sakhalin , Japanese , Filipino , Large and Small Sunda , New Guinea , New Zealand , Tasmania ; in the central and southern parts there are numerous small islands. Mark the islands and seas of the Pacific Ocean on the map.

Bottom relief

The bottom relief is varied. In the east - East Pacific Rise , in the central part there are many depressions (North-East, North-West, Central, East, South, etc.), deep-water trenches: in the north - Aleutian, Kuril-Kamchatsky, Izu-Boninsky;

in the West - Mariana (with maximum depth

World Ocean - 11,022 m), Philippine and others;

in the east - Central American, Peruvian

other.

Currents

The main surface currents: in the northern part of the Pacific Ocean - warm Kuroshio, North Pacific and Alaskan and cold California and Kuril; in the southern part - warm South-Trade winds and East Australian and cold West Winds and Peruvian. Surface water temperature at equator from 26 to 29 ° C, in polar regions up to -0.5 ° C. Salinity 30-36.5 ‰.

Mark the currents of the Pacific Ocean on a contour map.

Flora and fauna of the Pacific Ocean

Economic significance

The Pacific Ocean accounts for about half of the world's fish catch ( pollock , herring , salmon , cod , sea \u200b\u200bbass and etc.). Mining crabs , shrimp , oysters .

• Important sea and air communications between the Pacific Rim countries and transit routes between countries run across the Pacific Atlantic and Indian oceans ... Large ports : Vladivostok , Find (Russia), Shanghai (China), Singapore (Singapore), Sydney (Australia), Vancouver (

  and.strong dissection in the west and east

  b.strong dissection in the west and weak in the east

  in.weak dissection in the west and strong in the east

  g.weak dissection in the west and east
  
  

  The widest part of the Pacific Ocean is located at ... latitudes

  and. equatorial and tropical

  b. tropical and temperate

  in. moderate and arctic

  arctic and antarctic
  
  

  The most specific type of water movement in the Pacific Ocean is ...

  and. ocean currents

  b. wind waves

  in. tsunami

  ebb and flow
  
  

  The analogue of the Gulf Stream (Atlantic Ocean) in the Pacific Ocean is the current ...

  and. Western winds

  b. Kuroshio

  in. North Pacific

  californian
  
  

  Ice in the Pacific Ocean is found mainly in its ... parts and. northern and central b. central and southern

  in. south and north
  
  

  The most diverse organic world in the Pacific Ocean is characterized by waters ...

  and. equatorial and tropical latitudes

  b. tropical and temperate latitudes c. temperate and arctic latitudes of arctic and antarctic latitudes
  
  

  The first Europeans saw the waters of the Pacific Ocean ...

  and. Magellan

  b. Balboa

  in. Drake G. Tasman
  
  

  The Pacific Ocean (a world map makes it possible to visually understand where it is) is a constituent part of the world's water area. It is the largest on planet Earth. In terms of water volume and area, the described object occupies half of the volume of the entire water space. In addition, it is in the Pacific Ocean that the deepest depressions of the Earth are located. By the number of islands in the water area, it also ranks first. Washes the shores of all continents of the Earth, except Africa.

  Characteristic

  As mentioned earlier, the geographical position of the Pacific Ocean is due to the fact that it occupies most of the planet. Its area is 178 million km 2. By volume of water - 710 million km 2. From north to south, the ocean stretches for 16 thousand km, and from east to west - for 18 thousand km. The entire Earth will have an area less than the Pacific Ocean by 30 million km 2.

  Borders

  Allows him to occupy an impressive area in both the Southern and Northern Hemispheres. However, due to the large amount of land in the latter, the water area noticeably narrows to the north.

  

  The boundaries of the Pacific Ocean are as follows:

  • In the east: washes the shores of two American continents.
  • North: Bordered by the southeastern part of Malaysia and Indonesia, the eastern edge of Australia.
  • In the south: the ocean abuts against the ice of Antarctica.
  • In the north: through the Bering Strait, separating American Alaska and Russian Chukotka, it merges with the waters of the Arctic Ocean.
  • In the southeast: it connects with the Atlantic Ocean (conditional border from Cape Drake to Cape Sternek).
  • In the southwest: it meets the Indian Ocean (conditional boundary from Tasmania to the shortest, meridionally located point off the coast of Antarctica).

  Challenger Abyss

  The peculiarities of the geographical position of the Pacific Ocean allow us to speak of its unique mark, which characterizes the distance from the bottom to the surface of the waters. The maximum depth of the Pacific Ocean, as well as the entire World Ocean as a whole, is almost 11 km. This trough is located in the Mariana Trench, which, in turn, is located in the western part of the water area, not far from the islands of the same name.

  For the first time they tried to measure the depth of the depression in 1875 with the help of the British corvette Challenger. For this, a deep-sea lot was used (a special device for measuring the distance to the bottom). The first recorded indicator during the study of the trench was a mark of slightly more than 8,000 m. In 1957, a Soviet expedition took up the measurement of the depth. According to the results of the work carried out, the data of previous studies were changed. It is worth noting that our scientists have gotten closer to the real value. The depth of the trench, according to the measurement results, was 11,023 m. This figure was considered correct for a long time, and was indicated in reference books and textbooks as the deepest point on the planet. However, already in the 2000s, thanks to the appearance of new, more accurate instruments that help determine various values, the real, most accurate depth of the trench was established - 10 994 m (according to research in 2011). This point in the Mariana Trench was named the "Challenger Abyss". The geographical position of the Pacific Ocean is so unique.

  The gutter itself stretches along the islands for almost 1,500 km. It has steep slopes and a flat, 1.5 km long, bottom. The pressure at the depth of the Mariana Trench is several tens of times higher than at shallow ocean depths. The depression is located at the junction of two tectonic plates - the Philippine and the Pacific.

  

  Other areas

  A number of transitional areas from the mainland to the ocean pass near the Mariana Trench: the Aleutian, Japanese, Kuril-Kamchatka, Tonga-Kermadek and others. All of them are located along the fault of tectonic plates. This area is the most seismically active. Together with the eastern transitional regions (within the mountainous regions of the western outskirts of the American continents), they form the so-called Pacific volcanic ring of fire. Most of the active and extinct geological formations are located within it.

  

  Seas

  The description of the geographical position of the Pacific Ocean must necessarily relate to the seas. There are quite a large number of them near the outskirts of the ocean coast. They concentrated to a greater extent in the Northern Hemisphere, off the coast of Eurasia. There are more than 20 of them, with a total area (including straits and bays) of 31 million km 2. The largest ones are Okhotsk, Barents, Zheltoe, South and East China, Philippines and others. Off the coast of Antarctica there are 5 Pacific reservoirs (Ross, Dyurville, Somov, etc.). The eastern coast of the ocean is uniform, the coast is poorly indented, inaccessible and has no seas. However, there are 3 bays here - Panama, California and Alaska.

  

  Islands

  Of course, a detailed description of the geographical position of the Pacific Ocean also includes such a feature as a huge amount of land located directly in the water area. There are more than 10 thousand islands and island archipelagos of various sizes and origins. Most of them are volcanic. They are located within the subtropical and tropical climatic zones. Formed by a volcanic eruption, many of the islands are overgrown with corals. Subsequently, some of them went under the water again, and only the coral layer remained on the surface. It usually has the shape of a circle or semicircle. Such an island is called an atoll. The largest is located on the border of the Marshall Islands - Kwajlein.

  In this water area, in addition to small islands of volcanic and coral origin, there are also the largest land areas of the planet. This is quite natural given the geographical position of the Pacific Ocean. New Guinea and Kalimantan are islands in the western part of the water area. They respectively occupy the 2nd and 3rd place in terms of area all over the world. Also in the Pacific Ocean is the largest archipelago of the planet - the Great Sunda Islands, consisting of 4 large land areas and more than 1,000 small ones.

  The Great or Pacific Ocean is the greatest ocean on Earth. It accounts for about half (49%) of the area and more than half (53%) of the water volume of the World Ocean, and the surface area is equal to almost a third of the entire surface of the Earth as a whole. In terms of the number (about 10 thousand) and the total area (more than 3.5 million km 2) of islands, it ranks first among the rest of the Earth's oceans.

  In the northwest and west, the Pacific Ocean is bounded by the shores of Eurasia and Australia, in the northeast and east - by the shores of North and South America. The border with the Arctic Ocean is drawn through the Bering Strait along the Arctic Circle. The southern border of the Pacific Ocean (as well as the Atlantic and Indian) is the northern coast of Antarctica. When the Southern (Antarctic) Ocean is distinguished, its northern boundary is drawn along the waters of the World Ocean, depending on the change in the regime of surface waters from temperate latitudes to Antarctic ones. It passes approximately between 48 and 60 ° S. (fig. 3).

  Figure: 3.

  Borders with other oceans south of Australia and South America are also conventionally drawn along the water surface: with the Indian Ocean - from Cape South East Point at about 147 ° E, with the Atlantic Ocean - from Cape Horn to the Antarctic Peninsula. In addition to the wide connection with other oceans in the south, there is a communication between the Pacific and the northern part of the Indian Ocean through the inter-island seas and straits of the Sunda Archipelago.

  The area of \u200b\u200bthe Pacific Ocean from the Bering Strait to the shores of Antarctica is 178 million km 2, the volume of water is 710 million km 3.

  The northern and western (Eurasian) coasts of the Pacific Ocean are dissected by seas (there are more than 20 of them), bays and straits, separating large peninsulas, islands and entire archipelagos of continental and volcanic origin. The shores of Eastern Australia, southern North America and especially South America are usually straight and difficult to access from the ocean. With a huge surface area and linear dimensions (more than 19 thousand km from west to east and about 16 thousand km from north to south), the Pacific Ocean is characterized by a weak development of the continental margins (only 10% of the bottom area) and a relatively small number of shelf seas.

  Within the intertropical space, the Pacific Ocean is characterized by clusters of volcanic and coral islands.

  Ocean floor, mid-ocean ridges and transition zones

  Until now, there are different points of view on the question of the formation time of the Pacific Ocean in its modern form, but, obviously, by the end of the Paleozoic era, a vast reservoir already existed in the place of its basin, as well as the ancient foremother Pangea, located approximately symmetrically with respect to the equator ... At the same time, the formation of the future Tethys ocean in the form of a huge bay began, the development of which and the invasion of Pangea led to its further disintegration and the formation of modern continents and oceans.

  The bed of the modern Pacific Ocean is formed by a system of lithospheric plates, bounded from the ocean side by mid-ocean ridges, which are part of the global system of mid-ocean ridges. These are the East Pacific Rise and the South Pacific Ridge, which, reaching in places up to 2 thousand km wide, in the southern part of the ocean are interconnected and continue to the west, into the Indian Ocean. The East Pacific Ridge, stretching to the northeast, to the shores of North America, in the Gulf of California, connects with the system of continental rift faults of the California Valley, the Yosemite Basin and the San Andreas Fault. The middle ridges of the Pacific Ocean themselves, unlike the ridges of other oceans, do not have a clearly pronounced axial rift zone, but are characterized by intense seismicity and volcanism with a predominance of emissions of ultrabasic rocks, i.e., they have features of a zone of intensive renewal of the oceanic lithosphere. Throughout their entire length, the middle ridges and adjacent plate sections are crossed by deep transverse faults, which are also characterized by the development of modern and, especially, ancient intraplate volcanism. Located between the middle ridges and bounded by deep-sea trenches and transition zones, the vast Pacific Ocean bed has a complexly dissected surface, consisting of a large number of basins with a depth of 5,000 to 7,000 m and more, the bottom of which is composed of oceanic crust covered with deep-sea clays, limestones and silts of organic origin ... The bottom relief of the basins is mostly hilly. The deepest basins (about 7000 m or more): Central, West Mariana, Philippine, South, North-East, East Carolina.

  The basins are separated from each other or intersected by arched uplifts or block ridges on which volcanic edifices are planted, often crowned with coral structures within the intertropical space. Their tops protrude above the water in the form of small islands, often grouped into linearly elongated archipelagos. Some of them are still active volcanoes, spewing out streams of basaltic lava. But for the most part these are already extinct volcanoes, built on by coral reefs. Some of these volcanic mountains are located at a depth of 200 to 2000 m. Their peaks are leveled by abrasion; the position deep under water is obviously associated with the sinking of the bottom. Formations of this type are called guyots.

  The Hawaiian Islands are of particular interest among the archipelagos of the central part of the Pacific Ocean. They form a 2500 km chain stretching north and south of the Northern Tropic, and are the tops of huge volcanic massifs rising from the ocean floor along a powerful deep rift. Their apparent height is from 1000 to 4200 m, and the underwater one is about 5000 m. By their origin, internal structure, and appearance, the Hawaiian Islands are a typical example of oceanic intraplate volcanism.

  The Hawaiian Islands are the northern edge of a huge island group in the central Pacific Ocean, collectively known as Polynesia. Continuation of this group to about 10 ° S latitude. are the islands of Central and South Polynesia (Samoa, Cook, Society, Tabuai, Marquesas, etc.). These archipelagos tend to stretch from northwest to southeast, along transform fault lines. Most of them are of volcanic origin and are composed of basaltic lava strata. Some are crowned with wide and gently sloping volcanic cones 1000-2000 m high. The smallest islands in most cases are coral structures. Numerous clusters of small islands located mainly north of the equator, in the western part of the Pacific lithospheric plate, have similar features: the Mariana, Caroline, Marshall and Palau islands, as well as the Gilbert archipelago, which partially extends into the southern hemisphere. These groups of small islands are collectively called Micronesia. All of them are of coral or volcanic origin, mountainous and rise hundreds of meters above sea level. The coasts are surrounded by surface and underwater coral reefs that greatly impede navigation. Many of the smaller islands are atolls. There are deep ocean trenches near some of the islands, and to the west of the Mariana Archipelago there is a deep water trench of the same name, belonging to the transition zone between the ocean and the continent of Eurasia.

  In the part of the Pacific Ocean bed adjacent to the American continents, usually small isolated volcanic islands are scattered: Juan Fernandez, Cocos, Easter, etc. The largest and most interesting group is the Galapagos Islands, located at the equator near the coast of South America. It is an archipelago of 16 large and many small volcanic islands with peaks of extinct and active volcanoes up to 1,700 m high.

  Transitional zones from the ocean to the continents differ in the structure of the ocean floor and the peculiarities of tectonic processes both in the geological past and at the present time. They encircle the Pacific Ocean in the west, north and east. In different parts of the ocean, the processes of formation of these zones proceed differently and lead to different results, but everywhere they are distinguished by great activity both in the geological past and at the present time.

  On the side of the ocean floor, the transition zones are limited by arcs of deep-sea trenches, in the direction of which the lithospheric plates move and sink under the continents of the oceanic lithosphere. Within the transitional zones, transitional types of the earth's crust predominate in the structure of the ocean floor and marginal seas, and the oceanic types of volcanism are replaced by mixed effusive-explosive volcanism of subduction zones. Here we are talking about the so-called "Pacific Ring of Fire", which encircles the Pacific Ocean and is characterized by high seismicity, numerous manifestations of paleovolcanism and volcanic landforms, as well as the existence within its limits of more than 75% of the currently active volcanoes of the planet. This is mainly a mixed effusive-explosive volcanism of intermediate composition.

  All the typical features of the transition zone are most clearly expressed within the northern and western margins of the Pacific Ocean, i.e., off the coast of Alaska, Eurasia, and Australia. This wide strip between the ocean floor and land, including the underwater margins of the continents, is unique in terms of the complexity of the structure and the ratio between land and water area, it is distinguished by significant fluctuations in depths and heights, the intensity of processes occurring both in the depths of the earth's crust and on the water surface.

  The outer edge of the transition zone in the north of the Pacific Ocean is formed by the Aleutian deep-water trench, which stretches for 4000 km in a convex arc to the south from the Gulf of Alaska to the shores of the Kamchatka Peninsula, with a maximum depth of 7855 m. This trough, towards which the movement of lithospheric plates of the North Pacific Ocean faces, from the rear, it borders the underwater foot of the Aleutian Islands chain, most of them are volcanoes of the explosive-effusive type. About 25 of them are active.

  The continuation of this zone off the coast of Eurasia is a system of deep-water trenches, with which the deepest parts of the World Ocean are connected and at the same time the regions of the most complete and diverse manifestation of volcanism, both ancient and modern, both on island arcs and on the outskirts of the continent. In the rear of the Kuril-Kamchatka deep-water trench (maximum depth over 9700 m) is the Kamchatka Peninsula with its 160 volcanoes, of which 28 are active, and the arc of the volcanic Kuril Islands with 40 active volcanoes. The Kurils are the peaks of an underwater mountain range, which rises above the bottom of the Sea of \u200b\u200bOkhotsk by 2000-3000 m, and the maximum depth of the Kuril-Kamchatka trench running from the Pacific Ocean exceeds 10 500 m.

  The system of deep-water trenches continues to the south with the Japan Trench, and the volcanic zone continues with the extinct and active volcanoes of the Japanese Islands. The entire system of troughs, as well as island arcs, starting from the Kamchatka Peninsula, separates the shallow shelf seas of the Sea of \u200b\u200bOkhotsk and East China from the Eurasia mainland, as well as the basin of the Sea of \u200b\u200bJapan located between them with a maximum depth of 3720 m.

  At the southern part of the Japanese Islands, the transition zone expands and becomes more complex, a strip of deep-water trenches divides into two branches, bordering on both sides the vast Philippine Sea, the depression of which has a complex structure and a maximum depth of more than 7000 m.On the Pacific Ocean it is limited by the Mariana Trench with a maximum depth World ocean 11,022 m and the arc of the Mariana Islands. The inner branch, bounding the Philippine Sea from the west, is formed by the Trench and the Ryukyu Islands and continues further by the Philippine Trench and the arc of the Philippine Islands. The Philippine Trench stretches along the foot of the islands of the same name for more than 1300 km and has a maximum depth of 10 265 m. There are ten active and many extinct volcanoes on the islands. Between the island arcs and Southeast Asia, the East China Sea and most of the South China Sea (the largest in this region) are located within the continental shelf. Only the eastern part of the South China Sea and the inter-island seas of the Malay Archipelago reach depths of over 5000 m, and their base is a transitional type of crust.

  Along the equator, the transition zone within the Sunda Archipelago and its island seas continues towards the Indian Ocean. The islands of Indonesia have a total of 500 volcanoes, of which 170 are active.

  The southern region of the Pacific Ocean transition zone northeast of Australia is very complex. It extends from Kalimantan to New Guinea and further south to 20 ° S, bordering Australia's Sokhul-Queensland shelf from the north. This entire section of the transition zone is a complex combination of deep-water trenches with depths of 6,000 m or more, underwater ridges and island arcs separated by basins or shallow water areas.

  Off the east coast of Australia, between New Guinea and New Caledonia, lies the Coral Sea. From the east, it is limited by a system of deep-sea trenches and island arcs (New Hebrides, etc.). The depths of the Coral and other seas of this transitional area (the Fiji and especially the Tasmanov seas) reach 5000-9000 m, their bottom is composed of oceanic or transitional crust.

  The hydrological regime of the northern part of this area is favorable for the development of corals, which are especially common in the Coral Sea. From the side of Australia, it is limited by a unique natural structure - the Great Barrier Reef, which stretches along the continental shelf for 2300 km and reaches a width of 150 km in the southern part. It consists of individual islands and entire archipelagos, built of coral limestone and surrounded by underwater reefs of living and dead coral polyps. Narrow channels crossing the Great Barrier Reef lead to the so-called Great Lagoon, the depth of which does not exceed 50 m.

  On the side of the South Basin of the ocean floor between the islands of Fiji and Samoa, the second, external to the ocean, arc of troughs extends to the southwest: Tonga (its depth is 10,882 m is the maximum depth of the World Ocean in the southern hemisphere) and its continuation Kermadec, maximum depth which also exceeds 10 thousand m. From the side of the Fiji Sea, the Tonga and Kermadec troughs are limited by underwater ridges and arcs of the islands of the same name. In total, they stretch for 2000 km to the North Island of New Zealand. The archipelago rises above the underwater plateau that serves as a pedestal. This is a special type of structures on the underwater margins of continents and transition zones, called microcontinents. They vary in size and represent uplifts, folded by the continental crust, crowned with islands and surrounded on all sides by basins with oceanic crust within the World Ocean.

  The transition zone of the eastern part of the Pacific Ocean facing the continents of North and South America differs significantly from its western margin. There are no marginal seas or island arcs. From the south of Alaska to Central America, there is a strip of a narrow shelf with continental islands. Along the western coast of Central America, as well as from the equator along the outskirts of South America, there is a system of deep-sea trenches - Central American, Peruvian and Chilean (Atacama) with maximum depths of more than 6,000 and 8,000 m, respectively. Obviously, the process of formation of this part of the ocean and neighboring continents took place during the interaction of the then existing deep-sea trenches and continental lithospheric plates. North America pushed on and closed the troughs located on its way to the west, and the South American Plate moved the Atacama Trench to the west. In both cases, as a result of the interaction of oceanic and continental structures, collapse into folds occurred, the uplift of the marginal parts of both continents and the formation of powerful suture zones - the North American Cordilleras and the Andes of South America. Each of these structural zones is characterized by intense seismicity and the manifestation of mixed types of volcanism. O.K. Leontiev found it possible to compare them with the underwater ridges of the island arcs of the western transition zone of the Pacific Ocean.