Seas of the Pacific Ocean: list and interesting facts.

= Comprehensive landscape profile through Russia

INTRODUCTION

Introduction chapters:

• Seas washing the territory of Russia
  • Seas Pacific Ocean
• From the history of the geographical study of the territory of Russia
  • The initial period of scientific research on the territory of Russia
  • The period of major expeditionary research, including branch research
  • Soviet period of branch and complex research

Seas of the Pacific Ocean

The Pacific Ocean and its seas - Bering, Okhotsk and Japan - wash the eastern shores of Russia. The seas are separated from the Pacific Ocean by the Aleutian, Kuril and Japanese islands behind which are deep-sea trenches. The maximum depth of the Kuril-Kamchatka Trench reaches 9717 m. The seas are separated from each other by the Kamchatka Peninsula and Sakhalin Island. Eastern coast of Kamchatka from the mouth of the river. Kamchatka and up to Cape Lopatka is washed by the waters of the Pacific Ocean itself.

The seas occupy a boundary position between the largest continent of the planet and the largest of the oceans, in the transition zone from the continental to the oceanic crust. They are characterized by a smaller development of the shelf than that of the Arctic seas, therefore, significant expanses of the seas have great depths. Within each sea, a shelf, a continental slope, and a deep-sea basin located between the underwater parts of the mainland and island arcs are clearly traced, and in the Bering and Okhotsk Seas, the basin is shifted to the island arcs. In the Bering Sea, the deep-water basin is divided by the Shirshov Ridge into two rather independent parts: the western one - the Commander and the eastern one - the Aleutian. All of them have a fairly flat or flattened bottom. The seas of the Pacific Ocean are the largest and deepest off the coast of Russia. The Bering Sea is the largest and deepest (see Table 1). The shallowest of these seas is the Sea of ​​Okhotsk, its average depth is 1.5 times greater than that of the deepest of the seas of the Arctic Ocean - the Laptev Sea.

Table 1. Seas washing the territory of Russia

The total area of ​​the three seas is slightly less than 6 million km2, the volume of water is 6,744,000 km2, and the average depth is 1,354 m, which is more than 7 times the average depth of the seas of the Arctic Ocean.

The seas of the Pacific Ocean stretch for almost 5,000 km from northeast to southwest along the edge of the mainland. They are located in more southern latitudes than the seas of the Arctic Ocean, and are distinguished by warmer waters. All seas are semi-enclosed, they exchange water with the Pacific Ocean through numerous straits, but these straits are far from identical.

Thus, the Bering and Okhotsk seas freely communicate with the ocean through deep straits. The total width of all the straits of the Sea of ​​Okhotsk exceeds 500 km. The Bussol and Kruzenshtern straits are the widest and deepest ones here. The depth of these straits is more than 1000-2000 m. The waters of the Chukchi Sea practically do not affect the waters of the Bering Sea.

The Sea of ​​Japan is connected to the ocean only through several shallow straits (up to 150 m deep), so its water exchange is more limited and primarily affects the surface water layers, which is associated with more low temperature waters of the lower layer (0.4-0.6 ° C), despite the more southern position of the sea.

A distinctive feature of the water exchange of all seas Far East- a relatively small inflow of river waters into them. Only 19% of Russia's territory belongs to the Pacific Ocean basin. The total river runoff to these seas is 1212 km 2 /year. Compared to the total volume of water in these seas, this is very small.

From the Pacific Ocean, water enters the seas from the south, runoff from the mainland, mainly from the north. This causes counterclockwise circular currents: in the southeastern parts of the seas (near the island winds), the currents are directed from the south, i.e. warm, and in the northwestern parts, i.e. near the mainland coasts, currents are directed from the north and carry cold water.

The climate of the Pacific seas is largely determined by the interaction of land and ocean. Monsoon circulation evens out differences in the climate of the seas in winter time. The average temperature in January varies from -16°...-20° near the coast to -4°С near the island winds. Only in the Sea of ​​Japan in the southwest does the temperature rise to +5°C, but this is far from Russian territory. The most severe winter is in the Sea of ​​Okhotsk, at a distance of 500 km from the coast of which Oymyakon is located - the cold pole of the Northern Hemisphere.

From the spur of high pressure, stretching from the Asian high to Oymyakon, cold air masses enter the expanses of the sea.

In summer, the differences in the temperature regime of the seas are very significant. The difference of more than 30 degrees in latitude, of course, affects the total radiation and summer air temperatures over the waters of different seas. In the Bering Sea, the average temperatures in July are 7-10°С, in the Sea of ​​Okhotsk 11-14°С (in some years up to 18°С), in the Sea of ​​Japan 15-20°С (up to 25°С in the warmest years in the south). Typhoons and powerful cyclones sometimes penetrate the seas from southern latitudes, bringing hurricanes.

Thus, the seas of the Pacific Ocean are characterized by significant differences in the nature of the warm period and the smoothing of differences in winter.

In winter, the northern half of the Bering Sea and almost the entire Sea of ​​Okhotsk is covered with ice. A narrow strip of ice forms near the Russian coast even in the Sea of ​​Japan. In all seas, first-year ice of local origin is common. The most severe in terms of ice is the Sea of ​​Okhotsk, in the northwestern part of which the ice regime lasts 280 days a year. This is due to the general severity of the winter of this sea. Strongly chilled during the winter, the waters of the Sea of ​​Okhotsk warm up very slowly in summer. Even in the northern part of the Bering Sea, ice conditions are not so severe.

All seas of the Far East are characterized by low winter water temperatures: from 0 ... + 2°С to -1.3 ... -1.8°С. Summer temperature surface water in the Bering Sea they are 5-10°C, in the Sea of ​​Okhotsk - + 8-12°C, in the Sea of ​​Japan off the coast of Russia the water temperature is 17°C. The salinity of sea waters varies from 30-32‰ in the Sea of ​​Okhotsk to 33‰ in the Bering Sea and in the Sea of ​​Japan near our coasts.

The seas of the Pacific Ocean are characterized by tidal currents. In the Penzhina Bay of the Sea of ​​Okhotsk, the highest tides are observed off the coast of Russia - 13 m. In the area of ​​\u200b\u200bthe Shantar Islands, Tugursky and Sakhalin Bays, the tidal wave reaches 7 m, near the Kuril Islands - up to 5 m. In other areas, tides have a lower height.

The organic world of the Pacific Ocean finds favorable conditions for its existence. In shallow waters, under conditions of sufficient warming, abundant and diverse phyto- and zooplankton develop, lush thickets form seaweeds. Brown algae reach a length of several tens of meters, forming real underwater forests. The ichthyofauna is much more diverse than in the northern seas. Arctic, boreal, and in the Sea of ​​Japan and subtropical fish species live here. In total, about 800 species of fish live in the seas of the Far East, of which 200 species are commercial. The species diversity of fish in the Sea of ​​Japan is especially high (more than 600 species).

Salmon (coho salmon, chinook salmon, chum salmon, pink salmon), Ivasi herring, and Pacific herring in the Sea of ​​Japan are of great commercial importance. Of the bottom fish, cod, pollock, flounder and halibut are most widely represented. Sea bass, mackerel, tuna, conger eels are also caught here. There are crab banks in the Sea of ​​Okhotsk off the western coast of Kamchatka. The Commander and Kuril Islands are home to such valuable game animals as the fur seal and sea otter, or the sea otter (it is also found in the south of Kamchatka). When the Russian explorers reached the shores of the Pacific Ocean, the Steller's cow (sea cow) was found in large numbers near the Commander Islands, which has now been completely exterminated.

If distributed by the size of the seas, then the largest seas of the Pacific Ocean are:

1.Philippine Sea

2. Coral Sea

3. Sea of ​​Japan

4.Bering Sea

5. Tasman Sea

6. South China Sea

And these are the smaller seas of the Pacific Ocean: Okhotsk, Solomonovo, Fiji, New Guinea, East China, Yellow and many others. You can read more about the seas of the Pacific Ocean

Off the Asian shores of the Pacific Ocean are the South China, East China, Japan and Okhotsk Seas. The Bering Sea lies between North America and Asia. Several small seas are located between the islands of Polynesia, off the coast of Australia and Antarctica.

The seas of the Pacific Ocean can be listed and sorted out for a long time.

For example, here are the most big seas The Pacific Ocean is shown in the picture.



These are the Sea of ​​Japan, the Sea of ​​Okhotsk and the Bering Sea.

As for the other seas that are in the Pacific Ocean, they include. The Pacific Ocean includes: East China Sea, South China, Java, South China, Sulawesi, Sulu, Tasmanovo, Zhltoe, Philippine, as well as another huge the number of seas. You can watch this presentation

The Pacific Ocean includes the following seas: the Sea of ​​Okhotsk, the Bering Sea, the Sea of ​​Japan, the Yellow Sea, the Inland Sea of ​​Japan, the Philippine Sea, and the East China Sea. There are also seas that are between numerous countries South-East Asia: Javanese, South China, Sulawesi, Sulu, Bali, Flores, Banda, Savu, Halmahera, Seram, Moluccas Sea. Near the coast of Australia are the New Guinea Sea, the Coral Sea, the Solomon Sea, the Tasman Sea, and the Fiji Sea. Off the coast of Antarctica are the D'Urville Sea, the Ross Sea, the Somov Sea, the Bellingshausen Sea, and the Amundsen Sea.

So it turns out that most of the seas belong to the Pacific Ocean.

From the school geography course, we know that the following seas belong to the Pacific Ocean: the Sea of ​​Japan, the Bering Sea, the Yellow Sea, the Sea of ​​Okhotsk, the Philippine Sea, the South China Sea, the Tasman Sea, the Coral Sea, and the East China Sea. It is the Pacific Ocean that owns most of the seas on Earth and its area is 50% of the entire oceans.

The Pacific includes:

1. Sea of ​​Japan.

2. Sea of ​​Okhotsk.

3. East China Sea.

4. South China Sea.

5. Tasman Sea.

6. Yellow sea.

7.Philippine Sea.

8. Bering Sea.

The Pacific Ocean makes up 50% of its area of ​​the entire World Ocean.

The Pacific Ocean is the undisputed champion in the number of seas related to it. It occupies half of the entire vast area of ​​​​the water expanses of our planet. Here is a list of the seas, which, like tiny pieces of a puzzle, all together form an endless colossus of the mighty Pacific Ocean.

The Pacific Ocean is very huge and makes up half of the world's oceans. Therefore, it includes many seas. For example, the Pacific Ocean includes: the Philippine Sea, the Sea of ​​Okhotsk, the Bering Sea, the Sea of ​​Japan, the Tasman Sea.

A complete picture of all the seas of the Pacific Ocean can be viewed

The area of ​​the Pacific Ocean is 50% of the total oceans. The Pacific Ocean is located between the continents of Eurasia, Australia, North and South America and Antarctica. The Pacific Ocean includes seas and straits, the area of ​​​​which is 18% of the ocean area.

The Pacific Ocean is the largest ocean in terms of size, with the greatest average and maximum measured depths. The marginal seas of the Pacific Ocean include: Bering, Okhotsk, Japan, East China, Philippine, South China, Coral and Tasmanovo, as well as other, smaller seas of Indonesia, the New Guinea and Solomon Seas. In the Encyclopedia, the Arafura and Timor Seas refer to the seas of the Indian Ocean, and the Scotia Sea (also sometimes included in the Pacific Ocean) to the seas of the Southern Ocean. The Fiji Sea is included in the descriptions of the southwestern sector of the Pacific Ocean. The boundary between the northern and southern parts of the Pacific Ocean is the equator; the Galapagos and Gilbert Islands, located on the equator, belong to the South Pacific Ocean.

In addition to the marginal seas. The International Hydrographic Bureau distinguishes between individual marginal waters: the Gulf of Alaska (1533 thousand km3), Queen Charlotte, the Gulf of California (160 thousand km-) and the Bass Strait (70 thousand km2).

The Pacific Ocean extends 15,500 km from the Bering Strait to Cape Adair and 17,200 km from Panama to Mindanao, or 24,000 km if this line is extended to the Gulf of Thailand. The area of ​​the Pacific Ocean (together with the marginal seas) is 169,000,000 km2, the average depth is 4028

Pacific borders

The western boundary runs along the meridian from Singapore to the island of Sumatra (Strait of Malacca) (according to Kossin) or along the northern edge of the Strait of Malacca (according to the International Hydrographic Bureau), or along the linden northwest of the Pedro Peninsula (according to Murchson); then the border follows the line of the island of Sumatra - the island of Java - the island of Roti - the island of Timor. Opinions are divided whether the Timor and Arafura Seas and the Gulf of Carpentaria should be attributed to the Indian Ocean basin or to the Pacific Ocean basin.

Eastern border. All experts agree on the definition of Cape Horn as the boundary point. Further, the boundary goes along the meridian 68°04" W to the Antarctic Peninsula. The northern boundary passes with the Chukchi Sea.

Climate

In the northern hemisphere in winter, in the Pacific Ocean, in comparison with other oceans, the greatest zonal stability of atmospheric processes is observed, which is determined by the almost symmetrical arrangement of the main pressure centers in both hemispheres. In addition, in the Pacific Ocean there is a subtropical convergence zone with a wide belt of equatorial calm and two semi-permanent anticyclones: North Pacific, or Hawaiian and South Pacific. In the summer of the northern hemisphere, these anticyclones intensify and their centers are located at 40°N. sh. and 30°S sh. respectively. In the winter of the northern hemisphere, the North Pacific anticyclone weakens and shifts somewhat to the southeast. The South Pacific High does not change in the winter of the southern hemisphere. Due to the very cold Peruvian current in the east and the rise in temperature under the influence of the monsoons in the area of ​​Australia and the Solomon Islands in the west, the South Pacific anticyclone is shifting to the east.

trade winds spread on both sides of the equator up to 25 °, the southeast trade winds in the summer of the southern hemisphere shift somewhat north of the equator, in the same direction there is a slight movement of the thermal equator. The trade winds in the Pacific Ocean are less constant and usually weaker than the trade winds in other oceans. In the eastern parts of the Pacific, the trade winds are stronger and more noticeable. The thermal equator lies at about 5°N. sh., and on this parallel there are very heavy rains.

Monsoons quite significant in both the northwestern and southwestern Pacific Ocean. In the northwestern part of the summer of the northern hemisphere, the southeast monsoon affects the whole of Southeast Asia, most of China and the marginal seas of the Pacific Ocean up to 145 ° E. e. Mariana Islands and even south to the equator, where the same air flow expands with the southeast trade winds and the Australian anticyclone becomes the southeast monsoon of East India. The Southwest Pacific Ocean is subject to the northwest monsoon during the southern hemisphere summer, affecting the climate of New Guinea, Northern Australia, the Solomon Islands, New Caledonia and, to a lesser extent, the Fiji Islands.

While over most of the eastern half of the Pacific Ocean there is a very slight seasonal shift in the boundaries of the trade winds, in the western half there is a change in wind direction by 180 °. This is most noticeable in the Pacific Northwest, because during the northern hemisphere winter, the development of the Siberian High results in a strong outflow of very hard, dry northwest air, which creates a climate in Northeast China similar to that of the northeastern United States. But this climate is more severe, since the Canadian anticyclone is only rarely as strong as the Siberian one.

In the high latitudes of the North Pacific, a semi-permanent Aleutian cyclone (stronger in winter) is associated with a polar front that often travels from Japan to Alaska, and westerly winds are intensified by a strong winter runoff of cold air masses from Siberia. In summer, these conditions change due to a cyclone over Siberia and the Aleutian cyclone moves north and becomes much weaker.

In the same latitudes of the South Pacific Ocean, the Australian anticyclone, as a rule, does not block western disturbances, because the polar fronts pass mainly over the Southern Ocean, while heavy winter rains fall over Southeast Australia and the islands of New Zealand. Between the islands of New Zealand and the coast of Southern Chile, in the main westerly belt, there is not a single island at a distance of 8000 km.

Currents of the Pacific Ocean

The surface currents of the Pacific Ocean arise as a result of the trade winds and westerly winds. The surface flow is mainly westward at low latitudes and eastward at high latitudes. Near the continents, zonal flows deviate to the north and south and form currents along the eastern and western boundaries of the Pacific Ocean. A system of cyclonic and anticyclonic gyres is formed along the equator.

In the middle latitudes, large subtropical anticyclonic circulations prevail: western boundary currents (Kuroshio in the north and East Australian in the south. Parts of the western wind drift current, eastern boundary currents (California current in the north. Peruvian in the south). Northern and southern trade wind currents having a western a direction located a few degrees north and south of the equator.

In the higher latitudes of the southern hemisphere, there is the Circumpolar Antarctic Current, going east around Antarctica, and in the northern hemisphere, a subarctic circular circulation, consisting of the Alaska Current, the Kuril Current (Oyashio), going southwest along Kamchatka and the Kuril Islands, and parts of the North Pacific.
In the region of the equator, the North and South Trade-wind currents go westward, and between them in the band 5-10 ° N. sh. to the east is the Intertrade countercurrent.

The highest speed is observed in the Kuroshio Current (more than 150 cm/s). Velocities up to 50 cm/s are observed in the westerly flow near the equator and in the Circumpolar Antarctic Current. Velocities from 10 to 40 cm/s occur at the eastern boundary of the California and Peruvian currents.

Subsurface countercurrents have been found under the eastern boundary currents and along the equator. Under the Californian and Peruvian currents there are currents 50-150 km wide, directed poleward and extending from a horizon of 150 m down to several hundred meters. In the California Current system, the countercurrent also appears on the surface during the winter months.

The intertrade subsurface countercurrent is a narrow (300 km wide), fast flow (up to 150 cm/s) running at the equator to eastbound under the western surface current. This current is located approximately at a depth of 50-100 m and spreads from 160 ° E. to the Galapagos Islands (90°W).

Surface layer temperature varies from freezing at high latitudes to 28°C or more at low latitudes in winter. The isotherms are not always directed in latitude, since some currents (Kuroshio, East Australian, Alaska) carry warmer water towards high latitudes, while other currents (California, Peru, Kuril) carry cold water towards the equator. Moreover, the rise of cold deep water in the eastern boundary currents and at the equator also influences the distribution of heat.

Salinity of water surface layer reaches a maximum in the middle latitudes, where evaporation exceeds precipitation. Highest values salinity is slightly higher than 35.5 and 36.5 ppm. respectively in the northern and southern subtropical anticyclonic circulations. The salinity of water is much lower at high and low latitudes, where precipitation exceeds evaporation. The salinity of the waters of the open ocean is 32.5 ppm. in the north and 33.8 prom in the south (near Antarctica). Near the equator, the lowest salinity values ​​(less than 33.5 ppm) are observed in the eastern part of the Pacific Ocean. Under the influence of circulation, salinity is redistributed. The California and Peruvian currents carry low salinity waters from high latitudes towards the equator, while the Kuroshio carries high salinity waters from the equatorial region towards the pole; subtropical closed circulations turn out to be, as it were, lenses of water of high salinity, surrounded by waters of low salinity.

The oxygen concentration in the surface layer is always very close to saturation because the upper layers are in contact with the atmosphere. The amount of saturation depends on both temperature and salinity, but the role of temperature is much greater, and the overall distribution of oxygen on the surface largely reflects the distribution of temperature. The oxygen concentration is high in cold waters of high latitudes and low in warm equatorial waters. At greater depths, the oxygen concentration decreases. The degree of oxygen saturation is used as an indicator of the "age" of water - the time elapsed since the last contact of water with the atmosphere.

Top water circulation takes place under the influence of the wind. The adaptation of the density field to geostrophic equilibrium, as well as the convergence and divergence caused by the wind, lead to the formation of deep currents that are completely different from surface ones. At greater depths, where the circulation is mostly thermohaline, the differences are even greater in subtropical wind-driven anticyclonic circulations, there is convergence of the water surface, and the accumulation of water leads to the formation of a mixed layer (up to 300 m thick in the western Pacific during winter). Similarly, the divergence of surface waters in high-latitude cyclonic circulations leads to the rise of deep waters to the surface, and then to their spread to the periphery of cyclones. Along the coasts of North and South America at mid-latitudes, winds directed towards the equator cause surface water to move away from the coast, as a result of which deep water rises to the surface. At the equator, westerly winds and the rotation of the Earth cause surface water to move both south and north from the equator. which also leads to the rise of deep waters. Anticyclonic circulations are thus large lenses of less dense water. They are supported by wind-driven convergence of waters, as well as heating and evaporation.

In the subtropics of the Pacific Ocean, lenses of warm saline water propagate downward to a depth of more than 500 m. As a result, lenses of cold water of low salinity are formed here. A similar picture, although to a lesser extent, is characteristic of the equatorial region.

Characteristics of water masses and deep circulation. In the high latitudes of the North Pacific, surface waters are so low in salinity that even cooling to the freezing point will not give them sufficient density to sink deeper than the 200 m horizon. The deep waters of the North Pacific Ocean come from the South Pacific Ocean (since water exchange with the Arctic Ocean the ocean is small). These deep waters, which form in the Weddell Sea in the North Atlantic (where a certain temperature-salinity ratio forms very dense water on the surface), are constantly replenished.

Oxygen enters the surface waters of the ocean from the atmosphere. The waters sinking into the Weddell Sea in the North Atlantic are rich in oxygen, and they oxygenate the deep waters of the Pacific Ocean as they move north. Compared to the high oxygen content at the surface and at the bottom, the oxygen content at intermediate depths is much lower, and in some parts of the subtropical There is almost no oxygen in the northern part of the Pacific Ocean.

Distribution of nutrients in the Pacific Ocean depends on the water circulation system. Inorganic phosphates are consumed when plants grow on the surface and are regenerated at great depths when plants sink and decompose. As a result, nutrients are usually higher at depths of 1 to 2 km than at the surface. The deep waters of the Pacific Ocean are richer in phosphates than those of the Atlantic. Since the outflow of water from the Pacific Ocean occurs mainly due to surface waters, which are poorer in phosphates, phosphates accumulate in the Pacific Ocean, and their average concentration is approximately twice as high as in the Atlantic.

Bottom sediments

The longest sediment cores taken from the bottom of the Pacific Ocean reached 30 m, but most of the cores did not exceed 10 m. Experimental deep-sea drilling in two areas—near San Diego (California) and near Guadalupe Island—made it possible to significantly increase the depth of the study.

The total thickness of sediments in the Pacific Ocean is unknown. However, according to geophysical data, a layer of non-consolidated sediments is approximately 300 m. Under this layer there is a second layer about 1 km thick, which is represented by consolidated sediments and volcanic rocks, but a more complete picture of these two layers can be obtained only as a result of deep-sea drilling. While drilling for the Mohol project off the coast of Southern California, basalt was discovered under a 200-meter layer of sediment.

Volcanic precipitation

In some areas of the Pacific Ocean, there are layers of sediments, almost entirely consisting of fragments of unaltered volcanic rocks. Such material can spread over a large area in the event of surface eruptions. During underwater eruptions, the area of ​​distribution of such precipitation will be much smaller. Underwater alteration of volcanic silt and its mixing with other sediments leads to the formation of a continuous series of intermediate varieties of sediments of mixed origin. For volcanic sediments, lavas of the andesite and rhyolite type are the parent lavas, because their eruption is explosive and they are sufficiently resistant to secondary changes. Sediments near Indonesia, Central America, and in the Gulf of Alaska contain significant amounts of this kind of material. Basaltic volcanic sediments occur locally, due to the fact that the volcanic material of the basic composition, compared with the acidic, quickly decomposes with the formation of autogenous minerals. Modification of glassy clasts is one of the most important reactions resulting in the formation of aluminosilicates found in near-surface ocean sediments.

Coral reefs

Coral reefs are wave-resistant ecological features composed primarily of hermatypic corals and calcareous algae. Coral reefs border the continents and islands of the Pacific Ocean in areas where the temperature is at least 18 ° C. In the sediments of reef lagoons, coral fragments, foraminifera and fine-grained carbonate silt are found. Reef fragments spread along the edges of oceanic islands to the abyssal depths, where they undergo the same dissolution processes as foraminiferal calcium carbonate. On some coral islands, dolomite has been found at a certain depth. it also occurs in abyssal sediments near coral islands and is probably formed from calcium carbonate supplied from them, which expands in deep waters. In areas where there is little rainfall, coral rocks, as a result of reaction with phosphate from guano, are modified into phosphate rocks, consisting of apatite. The Lower Eocene phosphatized fauna was found on the Sylvania Guyot. There are also reactions of calcium carbonate with phosphates dissolved in sea ​​water; Early Eocene phosphatized fauna was found on the Sylvania Guyot.

History of the development of the Pacific Ocean

For more than a hundred years, scientists have been trying to solve one of the greatest mysteries of geology - to restore the tectonic history of the Pacific Ocean. In its size, structure, paleogeography, the Pacific Ocean differs from all other oceans of the globe.
The Pacific Ocean is the largest ocean on earth, with many more volcanoes, seamounts, and atolls at its bottom than all the other oceans combined. The Pacific Ocean is surrounded on all sides by the longest continuous belts of folded mountains, replete with active volcanoes, where earthquakes occur more often than in any other area of ​​\u200b\u200bthe globe. The propagation of seismic waves under the crust of the Pacific Ocean occurs at a shallower depth from the surface and at a higher speed than in other oceans.

The bottom of the central part of the ocean is covered with a thinner layer of sediments than in other oceans, so here you can better study the features of the underlying crust. All these features are enough to show why geologists and geophysicists consider the Pacific Ocean unique in geotectonic terms.

Geotectonic zoning within the Pacific Ocean clearly distinguishes between two physiographic provinces: 1) the main, or central. The Pacific basin and 2) marginal seas with numerous ridges and depressions of the second order located within them.

Pacific basin

In general, the bottom of the Pacific Ocean is a gently undulating abyssal plain; its individual parts are exceptionally aligned for tens and sometimes hundreds of kilometers. Its average depth is 5000 m.

This plain is traversed by numerous seamounts or volcanic ridges and countless elevations ranging from small hills to fairly massive (conical) seamounts. The East Pacific Rise, which is a continuation of the Mid-Ocean Ridge, extends from Antarctica to the southern tip of New Zealand, capturing the Pacific-Antarctic Ridge. The Easter Island Rise and the Galapagos Rise, and ends at America in the Gulf of California. In terms of its geomorphological features, this uplift is similar to other mid-ocean ridges of the Atlantic and Indian Oceans, but in its form it is surprisingly asymmetrical and deviates noticeably towards the American mainland. The small forms of its relief are the same as those of other submarine ridges of this type. The ridge is marked by a narrow rift or a series of graben structures, and most of the slopes are complicated by irregular (extending for about 1000 km) ridges and trenches located parallel to the uplift axis. The average height of these ridges is 2000-3000 m above the level of the bottom of the central part of the Pacific Ocean; in addition, it also includes local accumulations of small volcanic islands and seamounts. It can be assumed that the Juan de Fuca Ridge near Vancouver Island is a continuation of the main ridge.

Submarine fans and abyssal plains

Almost along the entire northeastern edge of the ocean there are numerous fans, quite large, which in some places pass into the abyssal plains. However, the number of the latter in the Pacific Ocean is small, since usually narrow oceanic trenches act as "traps" for sedimentary material, preventing further movement of turbidity flows.

Archipelagos of the Western and Central Pacific with volcanic islands, submarine rises and atolls. This area is characterized by rectilinear subparallel belts of volcanic islands, submarine ridges and atolls. Fan-shaped from the foothills of these underwater ridges diverge sediment cones, which everywhere form slightly inclined slopes, gradually merging with the ocean floor (approximately 5000-6000 m). An interesting feature of most underwater ridges (an example is the ridge whose peaks are represented by the Hawaiian Islands) is the presence of shallow depressions that almost completely surround the island slopes.

Archipelagos of the Central Pacific occupy 13.7% of its area. The height of the islands is different. An example high islands is the Tahiti chain, while the Tuamotu chain parallel to it is under water and is represented only by atolls on the surface. Main plain with low relief. It occupies most of the Pacific Ocean at a depth of 5000-6000 m. This plain is extremely flat, and there are no gentle slopes typical of abyssal plains, directed in one direction. The relief of the plain is rather undulating and is a system of conjugated low ridges and shallow depressions with elevations of about 300 m and distances between the tops of the ridges of about 200 km. In some areas, the maximum relative elevation does not even reach 60 m, while in others it can reach 500 m or more. Separate submarine ridges occasionally rise above the surface of the plain, but their number is small, with the exception of certain areas - island arcs or such specific provinces as the Gulf of Alaska.

Fault zones (linear ledges)

Large fault zones stretch for long distances (up to 2000 km), they cross the low relief plains of the northeastern sector of the Pacific Ocean and the East Pacific Rise.

Peripheral zone of island arcs and trenches

The boundaries of the main part of the Pacific Basin are fixed, as a rule, by a zone of deep-water trenches; from the side of the continents, these trenches are bordered rocky mountains or arcs of islands associated with one or more submarine ridges. In the western part of the Pacific Ocean, these island arcs and trenches are isolated and separated from the mainland by intermediate depressions, as a result of which the influx of sediments in the trench is insignificant, and most of them remain unfilled with sediments. These western trenches are extremely narrow, their bottom is flat due to a small influx of sediments. The slopes are steep, the steepness is 25-45°.

Along the eastern edge of the Pacific Ocean, the coastal Cordilleras are cut by large rivers that carry large amounts of sedimentary material into the depressions, in some cases completely filling them. The island arcs themselves are located on a double ridge; the outer islands are inherently non-volcanic, or at least not active volcanoes, while the inner zone contains many active or very recently extinct volcanoes. This is the so-called famous "fiery belt" of the Pacific Ocean.

marginal seas

They are located only in the western part of the Pacific Ocean and separate the island arcs from the mainland. There are several secondary inland seas, they reach 500-1000 km wide and about the same length. The bed topography of these seas is exceptionally diverse and, like the main basin, reflects their tectonic history and existing sources of drift. According to sounding data, the following main types of relief are distinguished.

Volcanic hills- an exceptionally disorderly heap of hills with steep, precipitous slopes, similar to volcanic cones, which completely cover the bottom of more distant depressions, such as the Pandora depression.

abyssal plains- flat, even or slightly sloping plains covered with sediments brought by fast bottom currents, such as turbidity. It is hard to imagine how otherwise such plains could form. In addition, the surface of this type is always somewhat higher (50-100 m) in the place where sediments from the mainland enter the sea. For example, the Tasman Basin is slightly shallower in the northwest, just opposite the Sydney, Hawkesburn and Hanger rivers that flow into it. There is a similar shallow water in the northeast of the Fiji Sea, where the Rewa (powerful tropical stream) flows into it, pouring out from the Fiji Islands. The largest of the basins of this type has a depth of up to 5000 m, smaller basins are characterized by the smallest depths - from 2000 to 4000 m.

Areas of microcontinental blocks found in numerous areas; they are a heap of quasi-cratonic blocks of large and small sizes, sometimes the distance between these regions is only a few kilometers, but more often they are separated from each other by hundreds of kilometers. The Melanesian plateau is a complex of this type.

underwater plateau widely distributed in the Pacific Ocean at shallow or medium depths. Plateaus are separated from the mainland. Typical examples: the Coral Sea plateau, the Belloy plateau in the southwestern part of the Pacific Ocean. Their usual depth is 500-2000 m; numerous coral atolls rise from the surface of the plateau.

Ridges and uplifts of the transition zone. The entire region is crossed by positive structures: either wide domed uplifts or narrow, strongly dissected ridges. These structures are associated with small volcanoes, seamounts and sometimes atolls. The main line of the ridges is almost continuous and runs almost parallel to the main peripheral belt of island arcs and trenches. Some of them end on the surface with such islands as the Japanese, Philippine, New Guinea, New Caledonia, New Zealand, etc.

Troughs and deep sea trenches the transition zone is usually associated with the aforementioned positive landforms. They usually occur in pairs, i.e., a large uplift usually corresponds to an equally large parallel depression. It is interesting that a trench or depression is usually located on the mainland side of the ridge at the bottom of the Mediterranean or marginal sea, i.e. they have a completely opposite orientation than
peripheral belt of the Central Pacific Ocean.

Features of the structure of the Pacific Ocean. The Pacific Ocean is in many ways different from the rest of the world's oceans. It gave its name to three concepts: Pacific coastlines, Pacific volcanism, Pacific type of crust.

Pacific coastlines. Feature coasts of the Atlantic type is that the coastline cuts off the tectonic structures of the mainland; this is due to faults that extend along the coast with the subsidence of individual large tectonic blocks or, generally speaking, with disturbances in continuous structures that originally stretched from the mainland into the ocean. In contrast to the Atlantic, the Pacific type of coasts reflects the continuous, continuous linear strike of the Pacific Ocean systems of folded mountains, island arcs, and adjacent marginal depressions. The Pacific Ocean is a flooded foreland on which peripheral folded belts pile up. The main distinguishing feature of the Pacific type of coasts is parallelism, i.e. mountains, coasts, beaches, reefs, trenches tend to maintain linearity and are located on the periphery relative to the central part of the Pacific Ocean.

Parallel ancient terraces of various heights run along the main line of the Pacific-type coast; sometimes, within a few kilometers, the height changes by 1000 m. The main trend of the relief is positive. The secondary terraces of the Pacific type are less active, but their height is also unstable, the Pliocene terraces of Southeast Australia can reach a height of 2000 m (southern part of New South Wales). However, most of the coastline of the secondary type is characterized by faults, negative landforms predominate.

Pacific volcanoes Pacific lavas are mainly confined to the belts of the circum-Pacific folding, and not the central part of the Pacific Ocean. The main rocks are andesites, rhyolites and olivine basalts. The Atlantic type of volcanism is characterized by alkaline lavas; it is regionally associated with stretch or shear zones.

Pacific bark. Based on geophysical studies of the earth's crust, it has been established that the character of the Pacific Ocean's crust is somewhat specific, although there are areas with similar structures in other oceans. The most significant fluctuations in the values ​​of gravity Vening-Meines recorded over the peripheral arcs. Based on the data obtained, it can be assumed that there is an uncompensated mass deficit along the trenches and an excess mass under the island arcs. Mid-ocean ridges are characterized by the presence of lighter material in thick "roots".
Analysis of seismic data on earthquakes and sounding data shows that under a layer of water 5–6 km thick in the central part of the Pacific Ocean there is a layer of sediments with a thickness of 0.5–1.0 km - the “second layer” is, apparently, water-bearing igneous rocks. type of serpentinite; however, some geologists believe that this layer is formed by consolidated sediments. The second layer lies on the section of the Mohorović surface
Systematic surveys with a towed magnetometer in the Pacific Northeast showed the presence of alternating highly and weakly magnetized rocks, oriented from north to south, which had a lateral displacement due to large latitudinal faults.

Intermediate crust in the western Pacific. A wide zone of marginal seas, stretching along the western borders of the Pacific Ocean from the Bering and Okhotsk to the Coral and Tasman Seas, is almost one of interesting features Pacific Ocean. In other oceans there are marginal seas, but in no other ocean are these seas so large and so numerous; moreover, nowhere except the Pacific Ocean, they are located along the western border.

It is quite clear that the general geology of these marginal seas in the western Pacific is fundamentally different from the geology of the central Pacific. folded belts are calc-alkaline. The line between these two provinces in the western part of the Pacific Ocean also separates two huge physiographic regions: the central part of the Pacific Ocean and the western marginal seas.

Deep sea trenches and island arcs. The main part of the Pacific Ocean has another significant feature: an almost continuous belt of trenches or ditches runs along the chain of island arcs on the oceanic side and the coastal Cordillera. Similar landforms exist locally in other oceans, but they do not form a peripheral belt there. These belts correspond to strong negative gravity anomalies. Behind these belts, on the mainland side, there is a belt of positive gravity anomalies. Similar belts of positive and negative anomalies are also found in other oceans, but in the Pacific Ocean they are especially widespread. Several important points should be noted in the distribution of the Pacific island arcs.

island arcs found only in the western part of the Pacific Ocean, in the east they correspond to the coastal cordillera. Thus, both of these forms are similar in the geotectonic sense, but they are not identical, since there are marginal seas that are located between the continents and island arcs. Such seas also exist within the Antilles and Scotia arcs, which are quasi-Pacific structures protruding towards the Atlantic Ocean.

Island arcs usually consist of two rows of islands, with external line are islands of mostly non-volcanic origin, while the islands of the inner line are mostly volcanoes. On the outer arc, sediments of Mesozoic age are found that are dislocated and broken by normal faults. The distance between rows is usually 50-150 km. In some cases, volcanoes are completely absent on one of the arcs. The "fiery belt" of the Pacific Ocean is not continuous everywhere.

Island arcs, as the name implies, have the shape of a semicircle. The bend radius varies from 200 to 2000 km. However, in some cases, such as the Tonga and Kermadec trenches, both rows of islands are rectilinear. Deep-sea trenches and arcs are complexly interconnected with the seismic zone, which belongs to the most intense seismic belts of the globe.

The trace of the so-called uplifting fault surface as a whole is a uniform distribution of earthquake sources along a simple plane, but the epicenters do not really clearly reflect the levels of earthquake shocks. Some geologists believe that earthquake shocks are accompanied by faults, and many large zones of the western Pacific trenches are now well correlated with horizontal displacement faults.

Pacific Stability The question of the constancy of continents and oceans belongs to the philosophical aspect of geology. It was put forward for discussion in the last century, but has not yet been resolved. This issue is considered from three points of view: 1) biogeographic, 2) geochemical and geophysical, 3) geotectonic. Each of these points of view needs careful analysis.

Biogeographic transoceanic connections. At the Pacific Congress in 1971 in Honolulu, a large number of biogeographers persistently defended the idea of ​​a Polynesian continent, agreeing at least only on wide land bridges between the now completely isolated islands. This whole area was formerly the mainland, which subsequently divided into numerous groups of islands; broke away first Hawaiian Islands. Deep drilling in the Central Pacific atolls has found typical land snails at various epochal levels up to the Miocene at least (eg at 251 and 552 m).

The “island steps” that existed in ancient times, which are still found today, contributed to migration certain types from island to island. The Galapagos Islands rise at the intersection of the East Pacific Rise and short secondary ridges leading to Central and South America.

The Swedish botanist Scottsberg devoted his life to studying the flora of the Pacific Islands; on the basis of observational data, he came to the conclusion that there was once a Pacific flora, autochthonous (local), mainland, not associated with any flora North America, nor with the flora of any other neighboring continent.

The existing landforms in the area of ​​New Guinea, New Zealand, the Philippine Islands and the Fiji Islands are good evidence of the existence of connections between the continents (this includes shallow underwater ridges and platforms); in addition, there are good geological data.

The theory of the existence of a mainland bridge or isthmus is well suited to explain the marginal migrations throughout the periphery of the Pacific Ocean through the Aleutian Islands to the Bering Strait, through the Antilles and from South America to Australia and New Zealand. Geotectonics in most cases is not in conflict with the presence of such relationships. When explaining migration along the transantarctic line, two serious questions arise: the area between the Ross Sea and New Zealand. The tectonic structures of South America, extending through the Scotia arc, connect with the Mesozoic folds of West Antarctica, but then abruptly break off at the Ross Sea. From the Ross Sea to New Zealand or Australia, not a single ridge departs. Here, apparently, the separation of the bark took place;

He is a champion in many respects: here is the deepest earthly cavity, and the most powerful typhoons (despite the "mild" name). Here is the largest number of seas, which is natural, based on its size. Now we will look at the seas of the Pacific Ocean, a list of their names, learn something interesting about them.

How many seas are there in the world?

To start a conversation follows from the fact that it is impossible to count the number of seas in the world, as well as in the Pacific Ocean. After all, the sea is not a lake, it never has clear boundaries. Which part of the ocean is considered a sea and which is not - this is a decision, where often subjective, and even political and economic factors play an important role.

The list of terrestrial seas is constantly changing, especially in the part where we are talking about tiny seas. Some of them, in fact, are large bays. From time to time, scientists and economists gather at special conferences to clarify the “marine” lists at them. The latest UNESCO recommendations say that 59 water regions of the planet should be considered seas. But again, these recommendations always find their opponents.

Large seas of the Pacific Ocean

To please all points of view, we first highlight the 6 largest seas of the Pacific Ocean. The area of ​​each of them is more than 1 million km² or very close to it. The existence of these marine basins is indisputable, and no one doubts. So here are our champions:

Other Pacific seas, list

Having paid tribute to these giant seas, we will add the rest of the seas of the Pacific Ocean to the list. At the moment it looks like this (although we repeat - in different sources it may be slightly different):

1. Amundsen.
2. Yellow.
3. Visayan Sea.
4. East Chinese.
5. Sea of ​​Koro.
6. Camotes.
7. Sea of ​​Mindanao.
8. Moluccan.
9. New Guinea.
10. Savu.
11. Samar.
12. Seram.
13. Sibuyan.
14. Sulu.
15. Sulawesi.
16. Solomonovo.
17. Okhotsk.
18. Fiji.
19. Flores.
20. Halmahera.
21. Javanese.

If we have singled out separately the largest seas of this ocean, we will pay tribute to the smallest ones. Although with them, as already mentioned, there are most controversial points. As a rule, these seas are bays, parts of larger seas (and sometimes just large "pockets" between large islands). The big problem is the definition of their boundaries.

It seems to be the smallest on our list, completely owned by Japan. Its area does not even reach 2 thousand km². Aki separates the east and west of the Sea of ​​Japan. Despite the size, it is in the zone of this reservoir that the powerful monsoons of Southeast Asia originate. In addition, the Aki Sea is rich in fish, primarily mackerel.

The second from the bottom in our list in terms of area, only 40 thousand km² (although this is not so small compared to the previous sea). A paradise for divers, a calm place where storms rarely blow. Located between the islands of Bali and Java. The climate here is subequatorial, humid.

The area is 740 thousand km². Despite its small size, the Banda has great depths. It is located within the Malay Archipelago, in a zone of active seismicity. One of the faults in the earth's crust passes here, so the average depth reaches 2,800 meters.

It is warm all year round in its water area, the seabed is beautiful, which also attracts scuba diving enthusiasts. Interestingly, nutmeg was grown on the tiny Banda Islands until the 19th century, keeping their location a secret. It was the only place on Earth where this nut grew.

A little more interesting

There is a lot to be said about the Pacific Ocean. Still, because its area is larger than the area of ​​\u200b\u200bthe entire earth's land! The seas are the outskirts of this giant reservoir, but they also have their own characteristics and mysteries. We have already mentioned some, we will supplement what has been said with some more information:

• The Bering and Okhotsk seas are periodically covered with ice, although not continuous. Among the other seas of the Pacific Ocean, ice occurs only in the Sea of ​​Japan.
• The Sea of ​​Okhotsk has the highest sea tides in Russia.
• The Savu Sea is a "disputed area" of two oceans. Hydrologists have not decided: it is part of the Pacific Ocean or the Indian.
• The Yellow Sea is the shallowest in the ocean, its average depth is only about 60 meters. It cuts deep into the land, taking in a very large Huang He river. In spring, it overflows, carrying millions of cubic meters into the sea. dirty water mixed with sand. Given the shallow depths, this water is capable of tinting the entire sea area in a yellowish color for several months.
• The Java Sea is considered one of the youngest not only in the Pacific Ocean, but throughout the world. It was formed in the last quarter ice age, and until that time it remained a dry land, along which, probably, the ancestors of people came to the lands of Australia from Asia.
• The Solomon Sea, which stretches east of New Guinea, is distinguished by a particularly restless geological nature. Two small oceanic plates collide here, so there are many sharp elevation changes in the sea. There are two depressions, each more than 9 thousand meters deep, as well as a number of underwater volcanoes. It is also distinguished by the richness of nature and numerous coral reefs.

Such a list of interesting facts could be continued for a long time. In the Pacific Ocean, you can find something special, your own, which distinguishes this sea basin from others. And this is the value, it is not for nothing that this ocean is often called the Great!