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 the horizontal and vertical distribution of the physical and chemical properties of 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).

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 the continental ice of Antarctica and Greenland - see . Ch. 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 terms of its geographical location, morphometric characteristics and natural conditions, the Arctic Ocean differs significantly 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.

Recently, a fifth ocean has often been 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 is the Mozambique Strait (almost 1800 km). Straits are very diverse; they play a 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).

02/10/2016 at 21:20 · Pavlofox · 71 640

The saltiest seas in the world

There are about 80 seas all over the world, which are an integral part of the World Ocean. All these waters are salty, but among them there are record holders, which are distinguished by a high concentration of salts and other minerals in their composition. The Baltic Sea is considered the freshest sea on the planet, its salinity is only 7 ‰ (ppm), which is equal to 7 grams per 1 liter of water. Among all the others, we singled out the saltiest seas in the world.

10. White Sea | Salinity 30‰

It is considered one of the saltiest seas in the world. Salinity here can reach 30‰ in places. This is one of the smallest seas in Russia, with an area of ​​90,000 square meters. km. The temperature here rises to 15 degrees in the summer and drops to minus 1 degree in the winter. The inhabitants of the White Sea are about 50 species of fish, including beluga whale, salmon, cod, smelt and others.

9. Chukchi Sea | Salinity 33‰

It is one of the ten saltiest in the world. Its salinity in winter is higher and can reach 33‰. It is located between Chukotka and Alaska on an area of ​​589,600 sq. km. The water temperature here is quite low: in summer – 12 degrees above zero, and in winter – minus 1.8 degrees. Walruses, seals, as well as fish - grayling, polar cod, Far Eastern navaga, Arctic char and others live here.

8. Laptev Sea | Salinity 34‰

Occupying an area of ​​662,000 sq. km., is considered to be the saltiest in the world. It is located between the New Siberian Islands and the Severnaya Zemlya Islands. The salinity of its waters reaches 34‰ in some places, and the water temperature does not rise above 0 degrees all year round. Walrus, sterlet, sturgeon, perch and other animals live in the depths of the sea.

7. Barents Sea | Salinity 35‰

Having a salinity of 35‰, it is one of the saltiest on earth and the saltiest in Russia. It is washed by the waters of the White Sea and has an area of ​​1,424,000 sq. km. In winter, only the southwestern part of the sea does not freeze; the temperature here in summer does not exceed plus 12 degrees. The underwater world here is quite rich in fish, including capelin, perch, herring, catfish, killer whale, beluga and others.

6. Sea of ​​Japan | Salinity 35‰

Located between the shores of Eurasia, the Japanese islands, and the island of Sakhalin, it is considered one of the saltiest in the world. Its salinity reaches 35‰. The annual water temperature ranges from 0–+ 12 degrees in the north, and in the southern part 17-26 degrees above zero. The fauna here is very rich and includes many species of fish. Herring, pollock, navaga, flounder, pink salmon, chum salmon, anchovy, crabs, shrimp, oysters, squid and many others live here. Japanese salt waters occupy an area of ​​1,062,000 sq. km.

5. Ionian Sea | Salinity 38‰

considered the densest and saltiest in Greece. It is perfect for those who do not know how to swim and want to learn. In summer, the temperature here ranges from 25-26 degrees above zero, and in winter it drops to plus 14 degrees. The salinity of the sea is about 38‰. The inhabitants of salt waters are fish such as tuna, flounder, mackerel and others. The Ionian Sea occupies an area of ​​169,000 sq. km.

4. Aegean Sea | Salinity 38.5‰

Aegean It is one of the ten saltiest seas in the world. Its salinity is about 38.5‰. Due to the high salinity, after swimming in such water it is recommended to wash with fresh water, since a high concentration of sodium can adversely affect the skin and mucous membranes. Winter temperatures here are about 14 degrees above zero, and summer temperatures are plus 24 degrees. It is inhabited by octopuses, sardines, sponges and other inhabitants. It is located between the peninsulas of the Balkans, Asia Minor and the island of Crete. The Aegean Sea has existed for about 20,000 years. It was formed as a result of the flooding of the Egenida landmass and occupied an area of ​​179,000 sq.m. Its appearance led to the formation of the islands of Crete, Lesbos, Euboea and others.

3. Mediterranean | Salinity 39.5‰

Located between Europe and Africa. It is rightfully considered one of the saltiest seas in the world, with salinity reaching 39.5 ‰ in some places. It also belongs to the warmest seas of the World Ocean - the temperature here is plus 25 degrees in summer and minus 12 degrees in winter. It is inhabited by seals, sea turtles, as well as more than 500 species of fish, including sharks, stingrays, blennies, lobsters, crabs, mussels and many, many others.

2. Red Sea | Salinity 42‰

Located between Africa and Asia, it is one of the saltiest on planet Earth. Its salinity reaches 42 ‰, which is about 41 grams per liter of water. A very rich underwater world is concentrated here: sharks, dolphins, stingrays, moray eels and other living creatures are the inhabitants of the Red Sea. The water temperature is 25 degrees above zero all year round. In the Red Sea, the water is very well and evenly mixed. In winter, surface waters cool, become denser and sink, while warm waters from the depths rise upward. In summer, water evaporates from the surface of the sea, and the remaining water becomes saltier, heavier and sinks. Less salty water rises in its place. Thus, all year round the water in the sea is intensively mixed, and throughout its entire volume the sea is the same in temperature and salinity, except in the depressions. In addition, the sea boasts amazing transparency.

1. Dead Sea | Salinity 270‰

- the saltiest in the world, which is located on the border of Israel and Jordan. The mineral content is about 270 ‰, and the salt concentration per 1 liter reaches 200 grams. The composition of the salts of the sea differs significantly from all others. It consists of 50% magnesium chloride, and is also rich in potassium, bromine, calcium and many other mineral elements. Potassium salts are artificially crystallized from its water. The water here has the highest density, which is 1.3-1.4 g/m³, which completely eliminates the possibility of drowning. In addition to unique salts, the sea contains healing mud, which contains 45% salts. Its features are a high pH value of 9, as well as a bitter and oily taste. Sea temperatures can reach 40 degrees above zero, which creates intense evaporation and contributes to high density. If in other waters with high salinity there are diverse inhabitants, then in the waters of the Dead Sea it is impossible to meet them.

Readers' Choice:

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. A distinctive feature is that 80% of precipitation falls in the 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 of the Russian Federation, it 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. These are the Dead and Aral seas. 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.

Once a year, crowds of tourists flock to the South Korean Jindo archipelago: due to the increasing tides between its two islands, the waves recede on the sea - and a land road almost three kilometers long and forty meters wide opens, representing an analogue of the famous miracle of Moses described in the Old Testament . Tourists use this opportunity to walk along the exposed bottom, take pictures and collect shells.

Since seas appeared on our planet relatively recently, from 20 to 2 million years ago, they are considered young geological formations. The deepest reservoirs arose in places where large faults formed in the earth's crust as a result of the displacement of lithospheric plates. For example, the deepest sea in the world, the Philippine Sea, is considered so because of the trench located at its bottom, the depth of which exceeds 10.5 km, when the average depth of a sea reservoir is about 4 km.

A sea is a part of the World Ocean that is separated from it by areas of land or elevated underwater terrain that always have water communication with it, such as straits or bays. If the seas and oceans are not connected to each other in any way, then such a body of water is considered a lake, for example, the Caspian or Dead Sea.

Due to the fact that almost all marine bodies of water are located near the coast of the continent or are located inside the continent, and the speed of sea currents due to limited communication with the World Ocean is low, they differ from it in the level of salinity, depth, water structure, climate, topography, flora and fauna (the farther from the ocean, the more noticeable the difference).

Marine bodies of water may be part of another sea - in this case they are distinguished depending on the flora and fauna: endemics are often found among the inhabitants of the deep sea, as can be seen in the example of the Aegean, located on the outskirts of the Mediterranean Sea.

Salinity

An important characteristic of a sea body of water is its salinity, which they receive thanks to rivers that carry dissolved salts from the depths of our planet and carry them to the seas. True, their level of salinity differs significantly from each other. Thus, bodies of water with a high salt content (for example, the Red Sea is considered the saltiest sea in the world) have a higher level of salinity than in the ocean: thanks to active evaporation, part of the water goes into the atmosphere, and the salt goes to the bottom, where it gradually accumulates.

But low-salinity seas have a lower level of salinity than in the World Ocean, since due to climatic conditions the water evaporates slowly, which makes it possible for it to escape through the straits (the freshest sea in the world is the Baltic).

Temperature

Up to a depth of two hundred meters, the sea temperature depends on the geographic latitude and time of year: in areas with a hot climate, the water temperature will range from + 25 to + 30 ° C, in polar latitudes it can drop to -1.8 ° C (it does not freeze only thanks to dissolved salts in sea water).

But at great depths, water temperature indicators are affected by currents; the deeper they are, the colder the water (the Philippine Sea, the deepest sea in the world, at its lowest point has a temperature of about zero degrees).

As for the coldest sea body of water in the world, it is considered the East Siberian Sea, which is part of the Arctic Ocean: it is almost always covered with ice, and the water temperature in its northern part remains virtually unchanged throughout the year and amounts to -1.8° C, and in the south in summer the sea can warm up to five degrees above zero.

Tourists are recommended to relax on the Red Sea coast. It is located between the Arabian Peninsula and Africa and is the warmest sea body of water in the world. In summer the water temperature is +27°C, in winter it does not drop below +20°C.

Sea waves

Despite the fact that sea bodies of water are characterized by rather weak currents, the water in them moves even when in clear weather the sea surface seems perfectly flat. But the waves of the sea still beat against the shore - quietly, weakly, barely noticeably, but they constantly advance on the coast and retreat. They appear due to the wind, and their size depends on the strength of the air flow, which comes into contact with the water and, through friction, creates pressure on the crests of the waves (the shallower the depth, the smaller the waves). If there is no wind at all, then there is a swell and waves imperceptibly advancing on the coast.

Also characteristic waves are seiches - standing waves that rise and fall in the same place. This phenomenon lasts from several minutes to tens of hours. Despite the fact that the average wave height is thirty centimeters, it can easily vary from a few millimeters to five meters (it all depends on the topography of the coast and the depth of the reservoir). Seiches are not as harmless as they seem at first glance, and are primarily dangerous for small ships, boats and even people on the coast: suddenly rising high waves can “drag” a person under water.

Classification of seas

It is interesting that scientists still have not been able to come to a consensus on how many seas exist on our planet, since there are bodies of water that are difficult to classify and classify as a sea, lake or bay. Therefore, the official definition is questionable - and everyone puts them in the category that suits him most.

According to the International Hydrological Organization, there are sixty-three seas on Earth. Some scientists question these data, pointing out that many small marine reservoirs that are part of larger ones are not taken into account here, and therefore there are much more reservoirs of this type and their number is approaching a hundred.

To convince opponents, a map of the seas is cited as an example (it should be noted that in this list, many bays also fall into the category of seas, for example, the Persian, Bengal, and Mexican).

According to these data, there are about thirty seas in the Pacific Ocean, thirteen in the Southern Ocean, eleven in the Arctic Ocean, and six in the Indian Ocean. The number of marine bodies of water in the Atlantic Ocean causes the greatest disagreement among scientists and their number ranges from sixteen to thirty.

One of the most popular classifications is the division of seas according to the degree of their isolation from the ocean:

• Internal - located at a great distance from the ocean, have limited water exchange with it and are connected by one or several straits;
• Marginal - located near the ocean coast, are part of it and are located on the shelf;
• Interisland - are part of the World Ocean and are separated from it by a ring of islands, within which the rise of the relief slows down the water exchange of these seas with the ocean. An island in the sea or ocean is usually the top of a high underwater mountain or appears as a result of seismic activity (earthquakes, volcanic eruptions). Sometimes it is artificially created by people when they form an artificial island in the sea for their own needs (for example, during the construction of the Burj Al Arab hotel in the UAE).

Starting point

As a result of many years of observations, several centuries ago, scientists came to the conclusion that it is the level of the sea surface that is the ideal point from which to measure the height of objects both above and below it. Therefore, it was decided to consider it the absolute height, the zero reference point (in contrast, the relative height shows how higher or lower one point is relative to another).

It should be noted that altitude above sea level is a rather conventional concept, since our planet is not entirely round in shape and is slightly flattened at the poles. Due to the different salinity levels of the Atlantic and Pacific oceans and the constantly changing direction of air currents, the difference in height from the surface of the two oceans is about 20 cm.

For example, in Russia, the zero point is considered to be the mark of the Kronstadt footstock (a level gauge, which is a rod with divisions), which was installed in Kronstadt on the Baltic Sea coast.

But the depth and height in Western Europe are calculated using a level gauge installed in Amsterdam; the level of the Mediterranean Sea is calculated using a gauge installed on the coast of Marseille. Other continents also have their own reference level.

Sea vessels in human life

The sea significantly influenced the development of civilization: as soon as man built his first ship, he began to plow the sea in search of routes to new lands, make great geographical discoveries, discovering this or that continent or island in the sea, and develop trade, science, and art.

It is not surprising that he paid special attention to the development of maritime transport: throughout the history of mankind, ships have played an important role in the life of society. And even now, despite the huge number of alternative modes of transport, more than 60% of the world's transport turnover is carried out by ships.

Transporting cargo by ship is 40% cheaper (this is especially beneficial for small countries whose borders are by sea) than transporting it by rail. Recently, with the development of technology, ships began to move at a fairly decent speed and some of them are capable of accelerating to 100 km/h).

In addition, the depths of the sea conceal a huge amount of natural resources (for example, oil), which man has learned to extract and use. Since almost all oil fields are located in the sea, and some are many kilometers from the coast, it was with the help of ships that people were able to reach minerals.

Thanks to ships, people were able to develop fishing: about 90% of the catch is caught in the seas and oceans (most fish are caught in the northern hemisphere). Unfortunately, for many fishermen, fishing is a real hunt, and therefore is often carried out uncontrolled, which leads to the disappearance of many rare species of marine life. There is hope that this process can be brought under control and poaching will be replaced by rational forms of fishing.