Home / Our children/ What is the continental shelf? The shelf, its role and significance for humans A geological “mess” at the edge of the ocean.

What is the continental shelf? The shelf, its role and significance for humans. Geological “mess” at the edge of the ocean.

You can find out what a shelf is from school curriculum in geography. These are oceanic areas of the bottom, relatively shallow (up to a couple of hundred meters).

In addition to the oceans, the shelf is also distinguished in the internal and marginal seas, which border islands, continents, and are also located in the depths of the continents (inland seas, for example, the Azov Sea).

Shelf measurement

Obviously, the shelf boundary on the continental side is the coastline, while the outer boundary is individual for each sea or ocean. It is carried out in a place where the depths increase sharply, along the edge. The limits of the shelf width can vary greatly - from a couple of tens of meters (typical of islands) to half a kilometer from the coastline (peninsulas, interior parts of continents). The widest shelf is in the Sea of Japan. The shelf edge may not be clearly defined, for example, where large rivers flow into the sea. In such places it is customary to mark a 200-meter shelf boundary.

The shelf is about 8% of the entire area of the World Ocean (its bottom), which is approximately 31 thousand square kilometers. The average depth of the shelf part is 132 m, and its width ranges from 1-3 m to 1500 km. The shelf part of the World Ocean contains minerals, most often oil, natural gas, and metals - gold, platinum, tin, zirconium, titanium. Even diamond deposits have been found on the shelf.

Examples of using the word

All examples of the use of the word “shelf” are associated with the description of the sea (ocean) bottom. More often given word used to describe the drilling process for gas and oil production, which is often carried out on the deep-sea shelf.

You can find out more details about any term, unfamiliar word and examples of their use by reading our section.

SHELF (a. shelf; n. Schelf; f. plateforme сontinentale, plateau сontinental; i. plataforma, plataforma сontinental) - relatively shallow (up to several hundred meters) areas of the bottom of the oceans, marginal and inland seas bordering continents and islands. The shelf boundary on the land side is the coastline, the outer boundary is drawn along the edge - an inflection point on the ocean side, below which the bottom depths increase sharply. The depth of the edge varies widely from tens of meters (islands, such as Cuba) to 400-500 (Labrador Peninsula) and even 600-700 m (Sea of Japan). Where the edge is not expressed in the relief (for example, deltas of large rivers, such as the Ganges), an isobath of 200 m is taken as the outer boundary of the shelf - the approximate average depth of the bend. The shelf area is 31,194 thousand km 2 (about 8% of the bottom area of the World Ocean), the average depth is 132 m, the width is from 1-3 to 1500 km.

There is no generally accepted classification of the shelf. There are continental and island shelves. Island shelves, as a rule, are shallower, narrower, and have specific relief and sediments. In addition, shelves of active and passive continental margins are distinguished. The shelves of active margins are characterized by high seismicity, increased heat flow, intense magnetic anomalies, and manifestations of volcanism. Morphologically, they are less pronounced than the shelves of passive margins: they are narrower, have a steep stepped slope, and are often fragmented by tectonic faults (for example, the borderland off the coast of California). O. K. Leontyev (1982) divides shelves into 3 groups of unequal distribution: transgressive, abrasive (or worked out), accumulative. Other classifications (G.S. Ganeshin et al., 1975) are based on geostructural criteria: platform, folded and geosynclinal shelves. It was proposed to classify shelves according to the type of their heterogeneity: tectonic, lithogenetic (ocean in the zone of large swell, ocean in the zone of constant storms, internal tidal and non-tidal seas, in the zone of predominance of calms, etc., P. A. Kaplin, 1977) . The classifications reflect different approaches their authors to the origin, position, and morphology of the shelf. Some consider it to be a completely continental morphostructure and define it as a submerged part of the land, while others consider it to be part of the ocean, developing under the influence of oceanic structures. There is also an approach to the shelf as a transitional (intermediate), but independent morphostructure, influenced by the processes of tectonogenesis, sedimentogenesis, and relief formation both from the land and from the ocean.

The process of formation of relief and sediments on the shelf is governed mainly by geographic zoning, although azonal facies and landforms (volcanic, tectonic and tidal) are also present. The shelf relief is mostly leveled. Shelf plains are almost everywhere complicated various forms meso- and microrelief tectonic (tectonic steps, fault ledges), subaerial (flooded river valleys, shafts, denudation remnants and ridges, etc.), subaqueous (formed by waves and currents of sand waves, ridges, riffles, drainage channels of compensation and rip currents) and coastal-marine or coastal genesis (elements of ancient coastlines - abrasion terraces, relict accumulative forms). Specific forms of shelf relief are underwater canyons, the origin of which is debatable. The dimensions of the canyons are extremely large, some of them begin within the coastal zone, cross the shelf, cut through the continental slope and end on the abyssal plains (for example, the length of the canyons of the Congo River is about 800 km, the cut into the bottom is 1100 m).

Sedimentary deposits on the shelf are represented by thick strata of terrigenous, carbonate, sometimes saline, continental and coastal-marine (passive margins), volcanogenic, marine and coastal-marine (active margins) sediments ranging in age from the Jurassic and younger. These deposits are partly deformed and, as a rule, are lowered along faults by 1-10 km (Atlantic coast of the USA). The newest shelf deposits include sediments of the late Pleistocene and Holocene. As a result of the Flemish transgression (17-6 thousand years ago), a complex sequence of sediments was formed on the shelf, consisting of subaerial (constituting 50-70% of all shelf sediments), coastal-marine (lagoonal, estuary, bar) and modern marine sediments. Relics of coastal relief and sediments formed at various hypsometric levels were buried in the thickness of these sediments. Subaerial sediments are relict. Significant role sediments caused by the activity of ice and marine organisms also play a role. As a result of the activity of various types of currents and waves, the clastic material (mainly coarse fragments) of the shelf experiences constant movement, migrating to the shore or to the edge. Within the shelf (especially near river mouths), the process of “avalanche sedimentation” occurs, as a result of which a significant amount of debris accumulates.

In Quaternary time, processes associated with glacioeustatic transgressions and regressions appeared on the shelf. During regression, the shelf was dried to a depth of approximately 100 m; subaerial sediments were deposited on the dried part and a subaerial relief was formed. Subsequent transgressions, the amplitude of which reached 100-110 m, partially destroyed the sediments and topography of previous regressive eras. Because the coastline migrated repeatedly across the upper shelf, early and middle Pleistocene subaerial relief and sediments are poorly preserved. During periods of glaciation, huge masses of glacial, fluvioglacial and alluvial material were transported and accumulated on the shelf. During rapid transgressions, this material was processed by waves and a significant part of it was thrown onto land in the coastal strip, and then formed into huge dune massifs and coastal accumulative forms.

When my uncle came home on vacation, I often went to visit him and listen to stories about his work on the shelf. Then I still didn’t understand who he worked for and what the meaning of his work was, but the mysterious word “shelf” was often heard from his lips. As an adult, I, of course, understood what my uncle was talking about and I began to seriously think about continuing his work.

What is a shelf

So what is a shelf? This is a continuation of the mainland under water. Its average depth is small, from 200 to 600 meters (it can reach one and a half kilometers). Between the shelf and the coast lies the so-called "edge". This is the transitional part between the land (seashore) and the seabed.

What types of shelves are there?

Soviet geologists made a great contribution to the study of engineering-geological processes developing at the bottom and in the adjacent coastal zone of the seas in the 70-80s of the last century. They developed the structure of the shelf according to geostructural characteristics:

orthoshelves(platform areas);
parashelves(in folded areas earth's crust);
hemishelves(in geosynclines - the most mobile elements of the lithosphere).

There is no generally accepted classification for shelves. But since the shelves border the islands and continents they are divided into: continental shelf (or arctic)(for example, the Russian continental shelf immediately adjacent to Russia) and island shelf. These shelves are neither deep nor wide. They are, in turn, divided into shelves of active continental margins(earthquakes and tsunamis are common here) and shelves of passive margins.

What are the shelves rich in?

The shelves are rich gas and oil. But their extraction is more difficult than on land, because the deposits are located under water. The depth of the sea in some places can reach 500 meters. Therefore, a complex technical structure was invented - blevel platform.

If the water depth is up to 40 meters, then stationary platforms are used (they are attached to the bottom with piles), and at greater depths they work semi-submersible platforms(standing on underwater pontoons). In order for a country to own the shelf adjacent to its shores, it is necessary to submit an application to the UN Commission for consideration. Nowadays, the greatest interest of the leading world powers is Arctic shelf. Russia and Russia are fighting for the rights to this shelf. Thus, oil production in the Russian sector of the Arctic shelf is projected to increase 3.6 times by 2030. Almost 30 countries are carrying out trial and commercial exploitation of mineral resources on the shelves. The Arctic shelves of our country are rich in flora and fauna. A polar bear became a symbol of the Arctic.

My uncle's stories not only gave me a comprehensive knowledge of what the shelf really was, but also defined my future profession. Now I work on an oil platform, helping our state in mining.

The continental shelf is an area of the ocean floor located between the average low tide level and the area of sharp change in the slope of the ocean floor, limiting the inner edge of the continental slope.

Submarine slope steepening occurs at an average depth of about 430 feet below present sea level (Shepard, 1963). It is believed that in the past this line was at a depth of about 600 feet, so neoceanologists usually call the 600-foot isobath the outer edge of the continental shelf. Average slope of the shelf zone globe is less than one-eighth of a degree, or about 12 feet per mile, with an average width of about 42 miles, the minimum being less than 1 mile and the maximum exceeding 750 miles (Shepard, 1963). The distribution of continental shelves on the globe is shown in Fig. 13.

Rice. 13. Continental shelves of the World Ocean (blackened).

Between the shelf edge and the deep ocean floor lies the continental slope.

Its width averages about 10-20 miles, and its slope is about 4°. Slopes with a steepness of 25° and sometimes even 45° are not uncommon (Trumbull, 1958).

Continental shelves can be considered as an underwater continuation of the marginal regions of the adjacent land, because, as a rule, their geological structure contains a lot common features with adjacent regions of the continent. Although the continental shelf is generally considered to be a flat, featureless plain, this part of the ocean is often home to canyons, trenches, and underwater rises. Glaciers, rivers, and coral structures take part in transforming the slope and depth of the continental shelf. In some parts of the shelf area, intensive accumulation of sediments occurs, in others - their erosion. Nowhere in other areas of the ocean are such dramatic changes in surface layer precipitation.

There are two types of continental shelves: wide, relatively shallow and monotonously flat, found near stable coasts vast plains land, and narrow, steeply inclined, with complex terrain, connected to the shores along which folded mountains stretch. The first type of continental shelf borders the eastern coast of the United States, the second type is developed along the western edge of the American continent.

Sediments within the shelf area are distributed unevenly, without a clear connection with depth and distance from the coast. However, some generalizations are still possible. Thus, sand is usually common in the open shelf zone, while clayey silts predominate in closed bays and inland seas. In the outer parts of open shelves, coarser-grained sediments are common and bedrock is exposed. The marine area of the extensive beaches is dominated by sandy sediments.

The rocks of the shelf zone are, as a rule, very similar to the strata developed in adjacent land areas.

Therefore, the mineral deposits of the continental shelf have much in common with deposits of the same minerals on the mainland, both in terms of the nature of occurrence and the quality of raw materials. This assumption seemed to be confirmed by the study of deposits in the Gulf of Mexico and offshore deposits off the California coast and other areas. However, since these conclusions are based on statistics on oil reserves in the Gulf of Mexico and California, they cannot be generalized to solid mineral deposits. The only exceptions seem to be sulfur deposits in the Gulf of Mexico, which are associated with salt domes.

History of shelf development

HYDRAULIC STRUCTURES

CONTINENTAL SHELF

There is another area (both geographical and water management construction) in which hydraulic structures are used - the continental shelf of the world's oceans.

Basic Concepts

The continental shelf (English: Shelf) is a continental shelf, a leveled part of the underwater margin of the continent, adjacent to land and characterized by a common geological structure. The shelf is limited on one side by the shore of the sea or ocean, on the other by the so-called edge, a sharp bend in the surface of the seabed, a transition to the continental slope.

The depth above the edge is close to 100–200 m (but in some cases reaches 500–1500 m, for example the southern part Sea of Okhotsk, edge of the New Zealand shelf).

The part of the mainland (continent) covered by ocean waters is its underwater margin and, in its geological structure and topography, continues the adjacent part of the land. Beyond the outer boundary of the underwater margin of the continent is the ocean floor (abyssal platform).

The underwater margin usually has three parts:

a) continental shelf - an underwater continuation of the continent, adjacent to land, characterized by a gradual slope of the bottom and shallow depths of the sea covering it;

b) the continental slope into which the continental shelf passes is characterized by a sharp and significant slope of the seabed;

c) continental rise (foot) - an elevation that is formed by sedimentary rocks sliding from the continental slope.

The total area of the continental shelf on the planet is about 32 million km2. According to various authors, the total area of ocean shallow water (up to 200 m deep) ranges from 7.5 to 12.1% of the water surface area.

The most extensive is the shelf of the Eurasian continent, covering 10 million km 2, while the shelves of the Northern and Western Europe occupy 2.6 million km 2, at the northern edge of Eurasia its width reaches 1.5 thousand km. The second largest area (up to 6 million km2) is occupied by the shelves of North America and Greenland. The third (4.5 million km 2) includes shelves along the Pacific coast and the islands of Indonesia. Next come the shelves South America(2.2 million km 2, of which almost 2 million km 2 are on the east coast and only 0.2 million km 2 on the western coast), Australia, New Zealand and Tasmania (more than 2 million km 2) and Africa (1 million km 2).

In the Northern Hemisphere the area coastal zone, enclosed between isobaths (isobath is a line connecting points of equal depths) 0 and 200 m, occupies 12.1% of the water surface (10.7 million km 2). In the Southern, more oceanic hemisphere, the ocean surface is larger, and here similar areas of the bottom make up only 3.9% of the water area (8 million km 2).

The average depth of the outer edge of the shelf of the World Ocean is 130–132 m, the average width is about 40 nautical miles (73–78 km). The most extensive in the world are the shelves of the Barents Sea (1300–1700 km) and other Arctic seas, as well as the coast of Argentina. In the center of the sea shelf of the Barents Sea, the depths reach 300–400 m, and on the edge in the trenches left by the glacier, 600 m. The maximum depths on the narrower shelves of the Labrador Peninsula (width 200 km) and the island of Newfoundland (width 500 km) are 800 and 1000 m. On the shelf of Patagonia - the southern tip of the South American continent - there are visible traces in the form of potholes (troughs - from the German das Trog - trough) - with depths of 200–700 m, which were left by the glacier. By the “fault” of the glacier, by the way, the Strait of Magellan arose, which is a system of fiords between Tierra del Fuego and the continent.

The legal status of the continental shelf and its belonging to a specific state is regulated by international agreements.

The first such agreement was the Geneva Convention of 1958, which for the first time defined the concept of the continental shelf and the basis of the legal regime for its use. The convention determined that the continental shelf is considered to be the coastal seabed to a depth of 200 m. One of the specific principles for the implementation of this convention was the conclusion of bilateral agreements between bordering countries on the procedure for using the shelf.

The UN Convention on the Law of the Sea was signed in 1982 (came into force in November 1994). Universal in terms of the number of participants and the set of objects subject to regulation, it determines the legal status of the continental shelf and the legal regime for its use as a spatial sphere and as a reservoir of natural resources. The 1982 UN Convention on the Law of the Sea has been signed by more than 160 countries and ratified by more than 60 of them. Interestingly, the United States refused to sign this document, reserving “the right to act at its own discretion.” In August 1984, England, France, Italy, Germany, Belgium, the Netherlands, Japan and the United States signed an agreement providing for these states the possibility of extracting seabed resources without any obligations in relation to other countries and decisions of the UN Convention on the Law of the Sea.

The basic principles of the UN Convention on the Law of the Sea are as follows.

The outer limit of the continental shelf, according to the 1982 Convention, runs along the outer limit of the submarine margin of the continent or at a distance of 200 nautical miles from the baselines if the outer limit of the submarine margin does not extend to such a distance.

If the outer limit of the underwater continental margin is located beyond 200 nautical miles, then the outer limit of the continental shelf is established along a line that connects fixed points determined by counting from the foot of the continental slope. Such points should not be more than 350 miles from the baselines from which the width of the territorial sea is measured, or 100 miles from the 2500-meter isobath.

The outer limit of the continental shelf beyond 200 miles is established using a special international procedure, which consists of the coastal state sending data on the boundaries of its continental shelf to a special international body - the Commission on the Limits of the Continental Shelf. The Commission makes recommendations to that coastal State regarding the establishment of the outer limits of its continental shelf.

The outer limits of the continental shelf established on the basis of such recommendations are final and binding on all states. The coastal state exercises sovereign rights over the continental shelf for the purpose of exploration and development of its natural resources.

Under natural resources refers to mineral and other non-living resources of the seabed and its subsoil, as well as “sessile species” of living organisms (organisms that, during the period of their commercial development, are attached to the bottom or move only along the bottom - crayfish, crabs, corals, sponges, shells, etc.). p.). The rights of a coastal state with respect to exploration and exploitation of the continental shelf are exclusive, meaning that without the consent of the coastal state, no other state can explore there or exploit its natural resources. The rights of a coastal state to the continental shelf do not affect the legal status of the waters covering it and the airspace above them. Since the maritime space above the continental shelf continues to be the high seas, all states have the right to navigate, fly, fish, and lay submarine cables and pipelines.

The coastal state has the right, for the purpose of exploration and development of natural resources of the shelf, to erect appropriate structures and installations and create safety zones around them (up to 500 m). The exercise of the rights of the coastal state should not infringe on the rights of navigation and other rights of other states.

The coastal state has the right to determine routes for laying cables and pipelines, permit the construction of installations and drilling operations, and the construction of artificial islands.

Why is so much attention paid to the continental shelf?

The fact is that the coasts of the seas and oceans have always been attractive for human activity.

Currently, 60% of the world's inhabitants live in a sixty-kilometer strip along the ocean shores. The population density here is 2.5 times higher than the average on the planet. Land areas along the sea coast are rightfully considered the “golden edge”, and their natural environment regarded as priceless wealth. The shallow ocean waters bordering the coast, the same one that is called the continental shelf, are no less rich in natural resources.

The attractive power of the sea coast as a habitat is determined not only by the favorable climate for life, but mainly by the food, mineral, energy resources, as well as the means of communication that the ocean provides. Cities such as Hamburg, Rotterdam, St. Petersburg, Shanghai, Calcutta, Amsterdam, Buenos Aires, New York, New Orleans and many other world centers of industry and trade arose in the most attractive land areas for settlement - in estuarine zones ( rivers flow into the sea) and the lower reaches of large lowland rivers connected by water arteries with the deep parts of the continent.

Of the more than 181 thousand species of bottom marine organisms living in the World Ocean, 180 thousand live in the coastal zone.

Their total biomass is estimated at 8–9 billion tons. Many species of marine animals have been used by humans for food since time immemorial. Up to 80–90% of the 1 billion tons of total biomass of higher marine organisms in the World Ocean is concentrated in coastal waters. 92% of all fish and 100% of shellfish and seaweed are currently harvested from the continental shelf.

On seabed coastal shallow waters are concentrated large number minerals. The wealth of the continental shelf includes oil, gas, sulfur, coal, iron ore, tin, sand, placers of ilmenite, rutile, zircon, magnetite, diamonds, gold, platinum, amber. On 50% of the continental shelf, 1,700 oil and gas fields have already been discovered (more than 100 billion tons of oil are extracted per year). “Marine oil” produced on the continental shelf accounts for 20% of global production. The search for and preparation for exploitation of deposits of alluvial minerals: titanium, magnesium, diamonds, gold and others is underway. The reserves of many shelf minerals are still simply not assessed.

History of shelf development

There is written evidence that since ancient times people have not only used biological resources shelf, but were also interested in its nature. So, in 450 BC. e. The ancient Greek historian and geographer Herodotus gave the first description of the Mediterranean shelf: “The nature of the Egyptian land is such that if, approaching it on a ship, one day’s journey from it you throw a lot, you will get silt even at a depth of 11 fathoms (20 m).” Herodotus also noted the fact that powerful sandy formations - deltas - usually develop in the estuarine areas of rivers. This term, by the way, comes from the name capital letter of the Greek alphabet Δ (delta), after the similarity with which the triangular Nile delta was named in ancient times.

Herodotus even suggested that Egypt was a gift of the Nile, referring to the fact that the river carried such a huge amount of solid material (140 megatons per year, now 88 megatons), which would have been enough to form not only its delta, but the entire territory of Egypt.

The ancient Romans figured out to take into account the peculiarities of the sea state when creating coastal aquatic farms. In the vicinity of Rome, located on the Tiber River, 27 km from its confluence with the Tyrrhenian Sea, the remains of three fish ponds were discovered. In ancient times, when the sea level was much higher than today, their aeration was periodically carried out by the surf during strong storms.

In 1502, during the construction of the port of Cesenatico, knowledge of the characteristics of the sea coast and the regime of sediment movement helped the genius of Renaissance engineering, Leonardo da Vinci, to take into account the along-shore movement of sediment and avoid silting of the port through the construction of enclosing piers. Obviously, it was in this regard that he uttered the wisest advice for marine researchers of all times: “When studying the movement of water, do not forget to draw a conclusion for practice from each discovered phenomenon, so that your science does not remain useless.”

Already in the 19th century, knowledge of the nature of bottom sediments helped North Atlantic fishermen determine their location on the shelf using so-called “Yorkshire beans” - small pebbles lifted from the bottom of shallow water. If the pebbles were able to be chewed, then it means that the ship was located to the west of the Dogger Bank, and if it was not possible, then to the east.

Usage problem marine resources, and the resulting problem of the economic division of the seabed territory also arose in the Middle Ages and went through a certain path of development.

Back in Ancient Rome there was a doctrine of the “business sea” (“mare nostrum”), the economic status of the seabed territories. However, then things did not come to the point of dividing it between states. In the 17th century, the Dutch legal scholar Hugo Grotius stated that “the sea cannot be exhausted either by navigation or by fishing, that is, by any of the ways in which it can be used.” For the economic development of the World Ocean, they proposed the concept of “res communis” - a thing that belongs to everyone. But already in 1911, having made sure that the reserves, for example, fur seals can be destroyed in just a few years, the United States, Russia, Japan and Great Britain (Canada) entered into the first agreement in the history of maritime law on the protection of ocean resources.

Then there were many such agreements and unilaterally adopted acts. The thirty-third President of the United States, Harry Truman, stated that all mineral resources(primarily oil) of the surrounding continental shelf belongs to the United States. In 1947, Peru declared its property fish that live within 200 miles of the coast, and included the water area in the country's territorial waters. By 1973, eight more states had joined Peru. In response to such claims, a UN resolution in 1970 declared that “the bottoms of the seas and oceans... as well as the resources... belong to all mankind.”

In 1977, the US also declared a 200-mile fishing zone. This was followed by Japan, Australia, and New Zealand.

These countries, unlike Peru, did not include such zones in the territory of the state. At the same time, the water area of Japan’s economic zone, for example, is 12 times larger than the territory of the country itself. By 1987, 114 coastal countries had already adopted similar laws - essentially, there was a political and economic division of 40% of the World Ocean, or 26% of the surface of the globe. Legal confusion has arisen between states regarding the use of marine resources.

In 1968, the USSR, by Decree of the Presidium of the Supreme Council, established sovereign rights to the exploration and exploitation of natural resources in the waters of its continental shelf.

And only the 1982 UN Convention on the Law of the Sea brought order to this issue.

By the way, regarding the issue of the size of territorial waters. For a long time The width of the territorial waters of coastal and island states was limited to limits established since the Middle Ages, and amounted to 3 miles - the maximum flight distance of a cannonball. The 1982 UN Convention expanded this limit to 12 miles (the range of visibility of the horizon from the bridge of a medium-sized vessel).

As already noted, the United States and some other countries refused to sign this convention, reserving “the right to act at their own discretion.”

Industrial development of the continental shelf for mineral extraction began in the 20th century. The construction of hydraulic structures on the shelf is the youngest type of water management construction.

The first oil wells in the Caspian Sea were drilled in the USSR in 1924 from artificial territories.

In 1933, the United States began oil production in the Gulf of Mexico. Norway produces oil in the North Sea. Work on the development of the continental shelf received its greatest development in the 60s of the 20th century.

SHELF (a. shelf; n. Schelf; f. plateforme сontinentale, plateau сontinental; i. plataforma, plataforma сontinental) - relatively shallow (up to several hundred meters) areas of the bottom of the oceans, marginal and inland seas, bordering continents and islands. The shelf boundary on the land side is the coastline, the outer boundary is drawn along the edge - an inflection point on the ocean side, below which the bottom depths increase sharply. The depth of the edge varies widely from tens of meters (islands, such as Cuba) to 400-500 (Labrador Peninsula) and even 600-700 m (Sea of Japan). Where the edge is not expressed in the relief (for example, deltas of large rivers, such as the Ganges), an isobath of 200 m is taken as the outer boundary of the shelf - the approximate average depth of the bend. The shelf area is 31,194 thousand km 2 (about 8% of the bottom area of the World Ocean), the average depth is 132 m, the width is from 1-3 to 1500 km.

There is no generally accepted classification of the shelf. There are continental and island shelves. Island shelves, as a rule, are shallower, narrower, and have specific relief and sediments. In addition, shelves of active and passive continental margins are distinguished. The shelves of active margins are characterized by high seismicity, increased heat flow, intense magnetic anomalies, and manifestations of volcanism. Morphologically, they are less pronounced than the shelves of passive margins: they are narrower, have a steep stepped slope, and are often fragmented by tectonic faults (for example, the borderland off the coast of California). O. K. Leontyev (1982) divides shelves into 3 groups of unequal distribution: transgressive, abrasive (or worked out), accumulative. Other classifications (G.S. Ganeshin et al., 1975) are based on geostructural criteria: platform, folded and geosynclinal shelves. It was proposed to classify shelves according to the type of their heterogeneity: tectonic, lithogenetic (ocean in the zone of large swell, ocean in the zone of constant storms, internal tidal and non-tidal seas, in the zone of predominance of calms, etc., P. A. Kaplin, 1977) . The classifications reflect the different approaches of their authors to the origin, position, and morphology of the shelf. Some consider it to be a completely continental morphostructure and define it as a submerged part of the land, while others consider it to be part of the ocean, developing under the influence of oceanic structures. There is also an approach to the shelf as a transitional (intermediate), but independent morphostructure, influenced by the processes of tectonogenesis, sedimentogenesis, and relief formation both from the land and from the ocean.

The process of formation of relief and sediments on the shelf is governed mainly by geographic zoning, although azonal facies and landforms (volcanic, tectonic and tidal) are also present. The shelf relief is mostly leveled. Shelf plains are almost everywhere complicated by various forms of meso- and microrelief: tectonic (tectonic steps, fault ledges), subaerial (flooded river valleys, moraine levees, denudation remnants and ridges, etc.), subaqueous (formed by waves and currents of sand waves, ridges, riffles , drainage channels of compensation and rip currents) and coastal-marine or coastal genesis (elements of ancient coastlines - abrasion terraces, relict accumulative forms). Specific forms of shelf relief are underwater canyons, the origin of which is debatable. The dimensions of the canyons are extremely large, some of them begin within the coastal zone, cross the shelf, cut through the continental slope and end on the abyssal plains (for example, the length of the canyons of the Congo River is about 800 km, the cut into the bottom is 1100 m).

Sedimentary deposits on the shelf are represented by thick strata of terrigenous, carbonate, sometimes saline, continental and coastal-marine (passive margins), volcanogenic, marine and coastal-marine (active margins) sediments ranging in age from the Jurassic and younger. These deposits are partly deformed and, as a rule, are lowered along faults by 1-10 km (Atlantic coast of the USA). The newest shelf deposits include sediments of the late Pleistocene and Holocene. As a result of the Flemish transgression (17-6 thousand years ago), a complex sequence of sediments was formed on the shelf, consisting of subaerial (constituting 50-70% of all shelf sediments), coastal-marine (lagoonal, estuary, bar) and modern marine sediments. Relics of coastal relief and sediments formed at various hypsometric levels were buried in the thickness of these sediments. Subaerial sediments are relict. Sediments caused by the activity of ice and marine organisms also play a significant role. As a result of the activity of various types of currents and waves, the clastic material (mainly coarse fragments) of the shelf experiences constant movement, migrating to the shore or to the edge. Within the shelf (especially near river mouths), the process of “avalanche sedimentation” occurs, as a result of which a significant amount of debris accumulates.

Numerous deposits of various minerals are known on the shelf.

Of greatest importance are oil and gas, whose reserves within the shelf are estimated at 100 billion tons and 15 trillion, respectively. m 3. Alluvial deposits, which are sources of titanium, zirconium, tin, chromium, diamonds, gold, platinum, etc., are also of industrial importance. Among non-metallic minerals, phosphorites have been identified within the shelf, as well as huge reserves of non-metallic minerals. building materials- sand and gravel, shell rock, coral limestone, which are widely used in construction. About 30 countries are carrying out trial and commercial exploitation of mineral resources on the shelf.

On the international legal regime of the shelf, see Art. World ocean.

Shelf (eng.shelf) - a leveled area of the underwater edge of the continent, adjacent

land and characterized by a common geological structure.

The boundaries of the shelf are the coast of the sea or ocean and the so-called edge (a sharp bend in the surface of the seabed - the transition

to the continental slope). The depth above the edge is usually 100-200 meters (but in some cases it can reach 500-1500 m, for example, in the southern part of the Sea of Okhotsk or the edge of the New Zealand shelf).

The total shelf area is about 32 million km². The most extensive shelf is at the northern edge of Eurasia, where its width reaches 1.5 thousand kilometers, as well as in the Bering Sea, Hudson Bay, South China Sea, and off the northern coast of Australia.

The 1982 UN Convention on the Law of the Sea gives coastal states the right to control the continental sea shelf (the seabed and subsoil of underwater areas located outside the territorial waters of the state). To exercise this right, the country must submit an application to a special international body - the UN Commission on the Limits of the Continental Shelf.

Bottom topography of the Barents Sea

HE gave Norway the waters and shelf of the Barents Sea.

Shelf (English shelf) is a leveled area of the underwater edge of the continent, adjacent to land and characterized by a common geological structure.

The boundaries of the shelf are the coast of the sea or ocean and the so-called edge (a sharp bend in the surface of the seabed - a transition to the continental slope). The depth above the edge is usually 100-200 meters (but in some cases it can reach 500-1500 m, for example, in the southern part of the Sea of Okhotsk or the edge of the New Zealand shelf). The total shelf area is about 32 million km². The most extensive shelf is at the northern edge of Eurasia, where its width reaches 1.5 thousand kilometers, as well as in the Bering Sea, Hudson Bay, South China Sea, and off the northern coast of Australia. The 1982 UN Convention on the Law of the Sea gives coastal states the right to control the continental sea shelf (the seabed and subsoil of underwater areas located outside the territorial waters of the state). To exercise this right, the country must submit an application to a special international body - the UN Commission on the Limits of the Continental Shelf. In Russia, Shtokman Development AG operates on the Barents Sea shelf. Oil is produced on the shelf of the Baltic Sea near the coast of the Kaliningrad region, oil, gas and other minerals are produced on the shelf of the Caspian Sea, and gas is produced off the coast of Sakhalin.

Shelf (English shelf) is a leveled area of the underwater edge of the continent, adjacent to land and characterized by a common geological structure. Wikipedia rules

I don’t know myself...

The shelf is the outskirts of the continent submerged by the ocean, and therefore there are the same minerals there as on land

Part of the continental crust

Shelf is a flattened area of the underwater edge of the continent. The boundaries of the shelf are the coast of the sea or ocean.

Shelf is a coastal shallow sea or oceanic zone with depths of up to 200 meters.

coastal shallow zone

Shelf/… Morphemic-spelling dictionary

A; m. [English] shelf] Special Coastal shallow ocean zone (with depths up to 200 m); continental shelf. ◁ Shelf, oh, oh. Shay zone. Sh y waters. Sh. ice. W y islands. * * * shelf (mainland shelf), leveled part of the underwater ... ... Encyclopedic Dictionary

- (continental shelf, continental shelf), the shallow part of the underwater margin of continents and islands, which has a relatively level surface and slight slopes. The shelf is confined to the area of development of the earth's crust of the continental type.... ... Geographical encyclopedia

- [English] Shelf shelf, shoal] 1. In oceanology, an area flooded by the sea, located on the periphery of a continent, i.e., an extensive continental shelf (flooded edge of the continent). On a global scale, the width of the sea varies from zero to 1500 km, amounting to ... Geological encyclopedia

- (English shelf) (continental shelf) a leveled part of the underwater margin of the continents, adjacent to the shores of the land and characterized by a common geological structure with it. The depths of the shelf edge are usually 100-200 m, but in some cases... ... Big Encyclopedic Dictionary

- (English shelf) 1) w. continental, a flattened edge of the continent submerged by the sea, passing below into the continental slope; The depth of the shelf edge is usually about 100-200 m; Within the shelf there are often deposits of various minerals... Dictionary of foreign words of the Russian language

- (English shelf), relatively shallow (mostly up to 200 m deep) and leveled areas of the bottom of oceans and seas, bordering continents. The width of the shelves is up to 1500 km, the total area is about 32 million km2. Oil, gas, sulfur are extracted within the shelf... Modern encyclopedia

SHELF, shelf, husband. (English shelf) (geographical). A shallow part of the sea formed from a submerged part of the land. Dictionary Ushakova. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary

SHELF, ah, husband. (specialist.). Coastal shallow ocean zone (with depths up to 200 m). Continental Highway | adj. shelf, oh, oh. Shelf zone. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary

Books

System of sea transportation of liquefied natural gas from the Arctic, Kasatkin R.G.. In the last decade, global oil and gas production will gradually mix from the continents, whose reserves are depleting, into the waters of the seas and oceans. With such significant changes in...
This mysterious shelf, G. Kaimashnikov, R. Korotky, M. Neiding. The popular science book talks about the shelf, its nature and resources, the extraction of liquid and solid minerals, unusual ships created for shelf development. The book also talks about...
Freshwater and marine animals of Kamchatka. Fish, crabs, mollusks, echinoderms, marine mammals, Smetanin Anatoly Nikolaevich. The morphological differences and features of the biology and ecology of commercial and other interesting species of aquatic animals inhabiting rivers, lakes, shelves and adjacent waters in…