Today there are 81 seas.
All seas are divided according to their location in the following directions: Atlantic, Pacific, inland seas and seas, with the Southern Ocean, North and Indian Ocean.
Types of seas
Traditionally, seas are usually divided into four groups:
- interisland,
- semi-closed,
- outlying,
- internal.
Inland seas are found "within" continents, but may have a connection to the ocean or other adjacent sea. Such seas are subject to great influence from land; the water level in them may be variable. These seas include: the Dead Sea, the Aral Sea and the Caspian Sea.
Some scientists and researchers consider the coastal sea to be a sea, and therefore they do not include inland seas and interisland seas in the general list.
Marginal seas are located on the edge of the land and have direct access to the ocean, but semi-enclosed seas are fenced by the mainland, but partially.
Interisland seas, based on the basis of their name, are located between different islands. The interisland seas include the following: Fiji, Java and New Guinea Seas.
Lack of seas
Compared to areas of land and land in general, the area of seas on the planet is small. There are even seas of garbage that are due to large quantity waste turns into a floating garbage dump, polluting the world's oceans. Such seas of plastic and other waste have been observed in the waters of the Indian and Pacific Oceans.
It is worth mentioning the disappearing seas. For example, the huge Aral Sea, due to the influence of human economic activity, began to disappear, the water seemed to evaporate. And all this happened due to water intake from other rivers, so fresh water stopped flowing into the Aral Sea. As a result, all the fauna that lived in this once huge sea simply disappeared, the climate of the area changed: where previously gardens bloomed and breezes blew, today there are only deserted dunes and the skeletons of ships that have rotted over time. This terrible tragedy region, which has not gone unnoticed in the world. Attempts were made to artificially resurrect the sea, but they were in vain. After more than half a century, it became obvious that only natural forces can restore the original balance of water and land; today the sea is slowly coming back to life.
The issue of the environmental situation and the issue of preserving water resources is becoming more acute every year: scientists suggest that climate change and the active expansion of man into the natural elements will wipe out more than one sea from the face of the planet, and a war between nations is not far off, not for territory, but for fresh and salt water.
Of the total area of the planet, equal to 510 million km 2, 361 million km 2 are occupied by the waters of the World Ocean, which is about 71% of the total surface area of the Earth. This predominance of water determines many of the most important features of the Earth as a planet - climate, life forms, the nature of the exchange of energy and matter between individual geospheres, etc. The world ocean contains 96.4% of the total amount of water found on Earth (including continental ice Antarctica and Greenland - see chap. 3), therefore its waters can be considered as an independent shell - oceanosphere. Despite the predominance of the water surface, the total amount of water compared to the size of the planet itself is small and is approximately 1/800 of the volume of the Earth. Consequently, on a planetary scale, the World Ocean is a relatively thin film on the surface of the Earth.
In accordance with the configuration of the coasts, bottom topography, water dynamics and atmospheric circulation, and the nature of the distribution of hydrological characteristics (temperature, salinity), the World Ocean is divided into separate oceans. Ocean- a vast part of the World Ocean, located between continents, with an independent water circulation system and specific features of the hydrological regime. In the process of evolution of our knowledge about the oceans, various options for dividing the World Ocean have appeared. It is generally accepted to distinguish four oceans: the Atlantic, Pacific, Indian and Arctic. Their morphometric characteristics are given in table. 10.1.
As can be seen from the table, the area of the Pacific Ocean is almost half of the entire area of the World Ocean and exceeds the surface of all continents and islands of the Earth. The Pacific Ocean has the greatest average depth; the Mariana Trench, the deepest in the World Ocean, is also located here. Its maximum depth is 11,022 m; it was measured by an expedition on the Soviet research vessel Vityaz in 1957.
Table 10.1.Basic morphometric characteristics of the oceans*
In my own way geographical location, morphometric characteristics and features natural conditions The Arctic Ocean is significantly different from other oceans. Its area is 12 times smaller than the area of the Pacific Ocean, 6 times smaller than the Atlantic Ocean and 5 times smaller than the Indian Ocean. The average depth of the Arctic Ocean is about three times less than that of other oceans. The ratio of the area of this ocean to the area of its drainage basin is 0.92, while for the Pacific Ocean this ratio is 0.04, for the Atlantic - 0.3, for the Indian - 0.09.
IN Lately a fifth ocean is also often identified - the Southern Ocean, which, in accordance with the above definition of the ocean, really represents an independent object with a specific regime. In the south it extends to the coast of Antarctica, but in the north it does not have a clearly defined border: it is drawn either along the northern border of the Antarctic Circumpolar Current or along a line connecting the southern ends of South America, Africa, Tasmania and New Zealand. The total area of the Southern Ocean is about 80 million km2. This means that the southern sectors of the three largest oceans will go to the Southern Ocean, and it will be second in area after the Pacific.
Within the oceans there are seas. Sea- a relatively small part of the ocean that juts into the land or is separated from its other parts by the shores of the mainland, seabed rises (thresholds) or islands and has specific features of the hydrological regime. The area of the seas is about 10% of the total area of the World Ocean, and the volume of water in the seas does not exceed 3% of the volume of water in the World Ocean. Based on the degree of isolation and location relative to the land, seas are divided into internal (Mediterranean), marginal and inter-island.
Inland seas usually protrude deep into the land and have difficult communication with the ocean through relatively narrow straits. In turn, inland seas are divided into intercontinental (for example, Mediterranean, Red) and inland (located within one continent, for example, Baltic, White, Black, Azov). The hydrological regime of these seas usually differs significantly from the regime of the adjacent part of the ocean.
marginal seas they protrude relatively shallowly into the land and are separated from the ocean by peninsulas, ridges of islands or rapids (for example, the Barents, Kara, Okhotsk, and Japanese seas). The water exchange of these seas with the ocean is greater than that of the inland ones, and the hydrological regime is closer to that of the adjacent part of the ocean.
Borders interisland seas are islands and seabed rises (for example, the Banda, Fiji, Philippine seas).
The total number of seas in the World Ocean according to the division adopted by the Intergovernmental Oceanographic Commission of UNESCO is about 60. The characteristics of the main seas are given in Table. 10.2. At the same time, a number of seas are distinguished only by states overlooking their coasts. For example, within the Mediterranean Sea the Tyrrhenian and Ionian seas are often distinguished; in the eastern part of the Barents Sea the Pechora Sea is distinguished, etc. The largest sea in the World Ocean and at the same time the deepest is the Philippine Sea (5.7 million km 2), the trench of the same name has a depth of up to 10,265 m. The volume of this sea is 30% greater than the volume of the entire Arctic Ocean. The largest seas in the Pacific Ocean, in addition to the Philippine Ocean, are the Coral Sea (4.1 million km 2), the South China Sea (3.5 million km 2), the Tasman Sea (3.3 million km 2), and in the Atlantic Ocean - the Weddell Sea ( 2.9 million km 2), Caribbean (2.8 million km 2) and Mediterranean (2.5 million km 2), in the Indian - Arabian (4.8 million km 2), and in the Arctic - Barents (1, 4 million km 2) and Norwegian (1.3 million km 2).
In the oceans and seas, there are also separate parts that differ in the configuration of the coasts, bottom topography and hydrological regime. First of all, these are straits and bays.
Strait- a body of water that separates two land areas and connects separate oceans and seas or parts thereof. An example is the Bering Strait, connecting the Pacific and Arctic oceans (and separating Asia and North America), the Gibraltar Strait, connecting the Mediterranean Sea with the Atlantic Ocean (and separating Europe and Africa), La Perouse between the islands of Sakhalin and Hokkaido, connecting the Sea of Okhotsk and the Sea of Japan. The width of the strait is considered to be the distance between land areas separated by water, the length of the strait is the distance between the main water bodies (between the inlet and outlet sections). The widest is the Drake Passage, which separates South America and Antarctica (about 1000 km), and the longest strait is the Mozambique strait (almost 1800 km). The straits are very diverse, they play very important role in the formation of the hydrological regime in the reservoirs they connect and in themselves represent an important object of study.
Table 10.2.Basic morphometric characteristics of some seas of the world*
* Atlases of the oceans. Terms. Concepts. Reference tables. GUNIO MO USSR, 1980.
Bay - part of the ocean or sea that juts out into the land and is not separated from it by islands or rises in the bottom. As a result, the bay’s regime differs little from the adjacent area of the ocean or sea. Examples include the Bays of Biscay and Guinea in the Atlantic Ocean, the Bay of California in the Pacific Ocean, the Bay of Bengal (the largest in area - 2.2 million km 2) and the Great Australian Bay in the Indian Ocean.
It should be borne in mind that the identification of individual seas and bays, as well as their boundaries, is a historical tradition, sometimes leading to contradictions. A number of regions of the World Ocean, having the same isolation and unique features of hydrological conditions, are in some cases called seas, in others - bays. For example, such ocean bays as the Mexican, Persian, and Hudson would be more correctly called seas; the Arabian and Beaufort seas are more likely bays, rather than the Sargasso Sea, which does not have shores, is essentially the inner part of the subtropical gyre of the North Atlantic.
Depending on the origin, shape, and structure of the shores, bays have different, often local names: bay, estuary, fiord, lip, lagoon, etc.
Bay- a small bay, separated by capes or islands from the main body of water (i.e. ocean or sea), usually well protected from the winds and often used for port construction. Each bay has a special hydrological regime. Examples of such water bodies are the Sevastopol and Tsemes bays on the Black Sea, the Golden Horn and Nakhodka in the Sea of Japan.
Liman - a bay separated from the sea by a sand spit (bar), in which there is a narrow strait connecting the estuary with the sea. Typically, an estuary is the flooded part of the section of a river valley closest to the sea (for example, the Dnieper-Bugsky, Dniester estuaries on the Black Sea coast). The characteristics of the waters in an estuary can be greatly influenced by the river flowing into it. These water bodies are sometimes classified as lakes, but it is more correct to consider them parts of river mouth areas (see Section 6.14).
Lip- a common name in northern Russia for a bay that protrudes deeply into the land, as well as a vast bay into which a river flows (Czech in the Barents Sea, Ob in the Kara). It is also advisable to classify these water areas as river mouth areas.
A narrow and deep sea bay with high shores (usually the bed of an ancient glacier) is called fiord(eg Sognefjord in the Norwegian Sea).
Seas are classified according to several criteria. One of them is belonging to a certain ocean. This means that the sea area has free access to the ocean, in most cases being part of it. There is also a division according to the degree of isolation. Let's consider all types.
Pacific Seas
This group is located in the Pacific Ocean and has more than two dozen seas. Here are the most significant of them:
This is a small open sea with an unusual climate. Distinctive feature 80% of precipitation occurs in summer. Typically, most rain or snow falls into a body of water during the winter.
Bali
Located next to the island of the same name. It is distinguished by warm water and a wide variety of underwater world, so scuba divers can often be seen here. The Bali sea is not very suitable for swimming due to the abundant coral thickets starting right off the coast.
Bering Sea
Located on the territory Russian Federation, is the largest and deepest sea in our country. It is located in a cold, northern region, which is why in some bays the ice may not melt for several years.
The Pacific Ocean group also includes such rarely mentioned bodies of water as the New Guinea, Molluscan, Coral Seas, as well as the Chinese and Yellow Seas.
Seas of the Atlantic Ocean
The largest seas of this group are:
Sea of Azov
This is the shallowest sea in the world, located on the territory of the Russian Federation and Ukraine. Despite its modest depth, many species of underwater creatures live here.
Baltic Sea
It has an unpredictable climate with frequent strong winds and fog. A sharp and unexpected change in weather makes this sea practically unsuitable for developed shipping.
Mediterranean Sea
The main difference between this reservoir is its size. It has borders with 22 states at once. Some scientists identify separate areas in its waters, which are also considered seas.
In addition, the group belonging to the Atlantic Ocean includes the Cilician, Ionian, Adriatic and many others.
Group of seas of the Indian Ocean
This group is the smallest. This includes the Red, Arabian, Timor, Andaman and other seas. All of them are characterized by rich underwater flora and fauna. And oil is produced in the Timor Sea.
Group of seas of the Arctic Ocean
The busiest sea of this group is the Barents Sea. It is located on the territory of Russia. Industrial fishing is carried out here, and oil production platforms operate here. In addition, the Barents Sea is one of the most important in the field of shipping.
In addition to it, the group also includes the Pechora, White, East Siberian and other seas. Among them there are bodies of water with unusual names, for example, the Prince Gustav Adolf Sea.
Seas of the Southern Ocean
The most famous sea from this group is named after Amundsen. It is located near the western coast of Antarctica and is always covered with a thick layer of ice. Also noteworthy is the Ross Sea, in which, due to the climate and the lack of predators, there are huge representatives of the fauna, which are characterized by much smaller sizes. For example, starfish here reach 60 centimeters in diameter.
The Southern Ocean group also includes the Lazarev, Davis, Weddell, Bellingshausen, Mawson, Riiser-Larsen seas and others.
Domestic
This classification is made according to the degree of isolation, that is, by connection or lack thereof with the ocean. Inland bodies of water are those that do not have access to the ocean. Another term applied to them is isolated. If the sea is connected to the oceanic expanses by narrow straits, then it is called internal semi-isolated.
Outlying
This type of sea is located “on the edge” of the ocean, one side adjoining the mainland. Roughly speaking, it is an area of ocean that, based on certain factors, is recognized as a sea. Marginal types can be separated by islands or large elevations of the bottom.
Interisland
This group is characterized by the presence of surrounding islands. The islands should be so dense that they prevent free communication between the sea and the ocean.
The seas are also divided into slightly and highly saline. Each sea on the planet is classified into several groups at once, since it can simultaneously belong to a specific ocean, while being slightly salty and located near the mainland. There are also two controversial bodies of water, which some scientists consider a sea, and others consider a lake. It's Dead and Aral Sea. They are small in area and completely isolated from the oceans. Although several decades ago the Aral Sea occupied a much larger area. The decrease in water resources here occurred as a result of rash human actions when trying to use water for irrigation of steppe lands.
Divided into separate parts (Fig. 1).
Rice. 1. Parts of the World Ocean
First of all, the World Ocean is a collection of individual oceans (Table 1).
Table 1. Main characteristics of the oceans (according to K. S. Lazarevich, 2005)
|
Total area, million km 2 |
Average depth, m |
Maximum depth, m |
Volume, million km 3 |
|
|
11 022 (Mariana Trench) |
||||
|
Atlantic |
8742 (Puerto Rico Trench) |
|||
|
Indian |
7729 (Sunda Trench) |
|||
|
Arctic |
5527 (Greenland Sea) |
|||
|
World Ocean |
11 022 (Mariana Trench) |
The basis for this division is the following characteristics:
- configuration of the coastline of continents, archipelagos and islands;
- bottom relief;
- independent systems of ocean currents and atmospheric circulation;
- characteristic features of horizontal and vertical distribution physical and chemical properties water.
The boundaries of the oceans are extremely arbitrary. They are carried out on continents, islands, and in expanses of water - along underwater elevations or, conditionally, along meridians and parallels.
Smaller and relatively enclosed parts of the oceans are known as seas, bays, and straits.
Classification of seas
Sea- a part of the ocean, usually separated by islands, peninsulas and surface hills. The exception is the so-called sea without shores - the Sargasso Sea.
Seas make up 10% of the world's oceans. The largest sea on Earth is the Philippine Sea. Its area is 5726 thousand km 2.
The seas differ from the open part of the ocean in their special hydrological regime and other natural features, which is due to some isolation, the large influence of land and slow water exchange.
Seas are classified according to different criteria. By location seas are divided into:
- outlying, which are located on the underwater continuation of the continents and are limited on the ocean side by islands and underwater hills (for example, the Barents Sea, Bering Sea, Tasman Sea; all of them are closely connected with the ocean);
- domestic (Mediterranean), which flow far into the land, connecting with the oceans through narrow straits, often with bottom rises - underwater rapids, sharply differing from them in hydrological regime. Inland seas, in turn, are divided into inland(for example, Baltic and Black) and intercontinental(for example, Mediterranean and Red);
- interisland, more or less surrounded by a dense ring of islands and underwater rapids. These include the Java, Philippine and other seas, the regime of which is determined by the degree of water exchange with the ocean.
By the origin of the basins seas are divided into:
- continental (epicontinental), which are located on the shelf and arose due to the increase in water in the ocean after the melting of glaciers during the advance of ocean water onto land. This type includes most marginal and many inland seas, the depths of which are relatively shallow;
- oceanic (geosynclinal), which are formed as a result of breaks and faults in the earth's crust and subsidence of the land. These mainly include intercontinental seas, the depths of which increase towards the center to 2000-3000 m and have basins that are relatively symmetrical in shape. They are characterized by tectonic activity, and usually they cut through the continental basement. All interisland seas are also located in zones of tectonic activity of the Earth, and the islands surrounding them serve as the tops of seamounts, often volcanoes.
The boundary between land and sea, the so-called coastline, As a rule, it is very uneven, with bends in the form of bays and peninsulas. Along the coastline there are usually islands, separated from the continents and from each other by straits.
Bay classification
Bay- part of the ocean that extends deep into the land. Bays are less isolated from the oceans and are divided into different types:
- fjords - narrow, long, deep bays with steep banks, jutting into mountainous land and formed at the site of tectonic faults (for example, Sognefjord);
- estuaries - small bays formed on the site of river mouths flooded by the sea (for example, the Dnieper estuary);
- lagoons - bays along the coast, separated from the sea by spits (for example, the Curonian Lagoon).
There is a division of bays according to sizes. The largest bay on Earth, both in area and depth, is the Bay of Bengal. Its area is 2191 thousand km2, and its maximum depth is 4519 m.
Essentially similar water areas can be called bays in some cases, and seas in others. For example, the Bay of Bengal, but the Arabian Sea, the Persian Gulf, but the Red Sea, etc. The fact is that their names have existed since historical times, when there were not enough clear definitions and ideas about water bodies.
Strait classification
Strait- a relatively narrow part of the ocean or sea that separates two areas of land and connects two adjacent bodies of water.
By morphology The straits are divided as follows:
- narrow and wide straits (the widest Drake Passage is 1120 km);
- short and long straits (the longest is Mozambique - 1760 km);
- shallow and deep straits (the deepest Drake Passage is 5249 km).
Based on the direction of water movement, they are distinguished:
- flowing straits, the current in which is directed in one direction (for example, the Strait of Florida with the Florida Current);
- exchange straits, in which currents pass in opposite directions off different coasts (for example, in Davis Strait, the warm West Greenland Current is directed to the north, and the cold Labrador Current is directed to the south). Currents in the Bosphorus Strait pass in opposite directions at two different levels (surface current from the Black Sea to Marmara, and deep one - vice versa).
