Baltic sea location. Baltic Sea: rest. Water temperature in the Baltic Sea. Coast of the Baltic Sea

1) Baltic Sea.
2) The Baltic Sea belongs to the basin of the Atlantic Ocean.
3). Its area is 415 thousand sq. km. For comparison, the Black Sea is 422 thousand sq. km., Azov, only 39 thousand sq. km. .sq.km. Beloe - 90 thousand sq. km. Karskoe - 883 thousand sq. km., Laptev Sea - 650 thousand sq. km., East Siberian - 901 thousand sq. km., Chukchi - 582 thousand sq. km. .km., Beringovo-2314 thousand sq. km., Okhotsk-1590 thousand sq. km. and Japanese - 978 thousand square kilometers. These are the seas washing Russia.
4)Temperature water in the Gulf of Finland in summer is 15-17 °C, in the Gulf of Bothnia 9-13 °C, in the center of the sea 14-17 °C. With increasing depth, the temperature slowly decreases. In winter, the average water temperature is + 6 * C.
5)If you look at the outlines of the sea, you can see its dissection. Its separate parts - Katgegat and the straits of the Small and Big Belt, form a natural transition between the Baltic and the North Sea, and in the north and east the bays adjoin the sea: Bothnian, Finnish and Riga.
6) The islands of the Baltic Sea - Muhu, Pel, Aland, Ven, Zeeland, Merket, Gotland, about, Haiumaa and others.
7) The Baltic Sea is an inland sea. Its volume is 21.5 thousand km³ , the average depth is 51 m, the greatest depth is 470 m. The deeper, the lower the temperature.
8) The salinity of the Baltic Sea is low, it has different layers in terms of salinity.
The salinity of surface waters is 7-8 ppm, at the bottom it is much saltier.
9) About a hundred rivers, large and small, flow into the Baltic Sea, of which
Neman, Vistula, Pregolya, Pene, Oder, Leba, Lielupe, Daugava, Pärnu, Narva, Ne-va, Turne-Elv and others.
10) Biological resources. - herring and cod, which make up about 90% of all production. In addition, flounder and salmon are caught. There are large stocks of crustaceans, as well as mollusks.
11) A large amount of chemical toxic waste has been dumped into the Baltic Sea. There are many ships sunk during the war, downed aircraft with undecontaminated ammunition., On the one hand, the waste waters of enterprises and factories are drained. And on the other hand, a huge amount of cargo is transported by sea and through it around the world.
12) The Baltic Sea is covered with ice in some places. . The largest ice cover is reached in early March, fixed ice occupies the northern part of the Gulf of Bothnia, the eastern part of the Gulf of Finland. And floating ice is in the center. In severe winters, the ice thickness reaches 1 m, and floating ice - 40-60 cm. Melting begins at the end of March, the sea is annually cleared of ice.
13) In question 10, the answer can be added that a lot of fish are still caught, such as salmon, herring, sprats.
14) Environmental problems are covered in question 11. It can be added that because of the runoff into the sea, a huge amount of algae began to grow in it, violating the ecosystem of the sea. Measures are needed to neutralize chemical waste from the sea.

The Baltic Sea is a sea located in Northern Europe, inland and belongs to the basin of the vast Atlantic Ocean.

Origin

The Baltic Sea lies on the stable Russian tectonic plate, the formation of which ended approximately 1.8-2 billion years ago.

30 million years ago, the plate occupied the position on which it is still holding. During the long ice age, which began about 700 million years ago, the entire territory of Northern Europe was covered with a thick layer of ice and snow.

Huge massifs of ice bent the mainland rock - thus creating a "hollow" for the future sea. And when the last ice age came to an end - two tens of millennia BC, all the ice melted and the Baltic Sea formed in their place.

The formation of the modern Baltic Sea took place in several stages, which should be discussed in more detail. First, the so-called Baltic glacial lake was formed, which happened fourteen thousand years BC. And ten thousand years BC, through the strait in Sweden, the territory of the modern sea was filled with sea water - this is how Yoldiev was formed.

Baltic Sea. storm photo

The Ancylo Sea dates back to 9-7, 5 millennia - when access to the oceans was closed. Around the middle of the eighth millennium, the sea merged with the ocean due to a rise in the ocean level to form the Lothyron Sea. And the modern Baltic Sea arises approximately in the fourth millennium BC.

Characteristic

The area of ​​the Baltic Sea reaches, excluding the islands, 415 thousand square kilometers. But the volume of water for a rather large sea reaches only 21.5 thousand cubic kilometers. Consequently, the depth of the Baltic Sea is small. The average depth is around 50 meters, and the greatest depth is only half a kilometer. The length of the coastline reaches approximately eight thousand kilometers.

The climate of the sea is temperate maritime, influenced by the Atlantic Ocean, from where cyclones come with westerly winds. Precipitation often falls, fog appears, especially in winter and spring. Storms are rare, and the wave height is not higher than 4 meters. The tides are almost invisible, usually no more than 20 centimeters.

Baltic Sea Kaliningrad region photo

In summer, the water temperature reaches an average of about eighteen degrees Celsius. In winter, and especially in February, it can reach zero levels. Coastal waters are frozen in the east and north, the southern and central parts of the sea are open. Only if the winter is very cold, then the whole Baltic Sea is covered with ice, but this rarely happens.

For the most part, the salinity of the water in the sea is extremely low (7 - 20 ppm), since many freshwater rivers flow into the sea. In turn, this served as a modest species diversity of local flora and fauna. However, low salinity plays an important role for humans. At critical moments, water can be available directly from the sea - but not for too long.

Unlike other seas, the Baltic can give you a short-term source of water, which can even save your life. But constant and long-term drinking of such water can be harmful to your health.

Which rivers flow into the Baltic Sea

The following large rivers flow into the Baltic Sea, which are also of great importance for industry and infrastructure:

• Western Dvina,
• Neva,
• venta,
• Pregolya, Narva,
• Oder
• Wisla.

Relief of the Baltic Sea

As already mentioned, the average depth of the seabed reaches fifty meters, since the sea is part of the continental shelf itself. At the bottom of the sea there are several basins and the depth of most of them hardly reaches two hundred meters, but the deepest of them goes down to 470 meters.

Baltic sea in winter photo

In the southern part of the sea, the bottom is flat, while in the north it is predominantly rocky.

Cities

Among the big cities on the Baltic Sea are St. Petersburg, Klaipeda, Svetlogorsk and Zelenogradsk, Jurmala, Pärnu and Narva, Albek, Binz and many others. All of them have become either favorite places for tourists or simply resort towns, where hundreds of thousands of people come to relax every year.

Animal world

The Baltic Sea is a very important industrial base, as it is the source of a huge number of fish of industrially important species. The species diversity itself in the world of fish is small, but the number of representatives of each species is impressive. A small variety of fish is due to the fact that the water in the sea is mostly fresh, and there are not so many freshwater fish.

Svetlogorsk, Kaliningrad region photo

In areas where there are more saline waters, the species diversity is somewhat greater, but still remains rather poor. At the very bottom of the sea, flounders and gobies live, as well as several species of mollusks and small crustaceans. In addition to them, worms also live on the seabed. There are several types of jellyfish in the Baltic Sea, among which there are quite huge species.

Of the small fish, schooling Baltic sprats and three-spined sticklebacks can be noted. In areas where fresh water is predominantly inhabited by such river species of fish as pike, perch, pike perch, roach, bream, burbot, whitefish, ide and some others, less common. Valuable industrial fish live in the Baltic Sea in huge sizes, and they include sprat, herring (constitutes about half of the total catch in the Baltic Sea), flounder, salmon, cod and eel.

seal in the Baltic Sea photo

The seals in the Baltic Sea are represented by only three species, among which are the gray seal, the pig, the common seal, or simply the common seal. Sharks also live in the sea, although they are represented by only one species that does not pose a danger to humans - these are small katrans. In rare regions, it is very rare to see the more dangerous herring shark.

• The northernmost point of the Baltic Sea is located right at the North Pole;
• The Slavs, in the time of Rus', called the Varangian sea, and all the inhabitants who sailed because of it - the Varangians;
• Between Germany and Russia, the Nord Stream gas pipeline was laid, which is located at the very bottom of the Baltic Sea;
• The Baltic Sea is also a huge base for oil production, which is now being carried out by the government of the Russian Federation;
• The Baltic Sea is heavily polluted with chemical waste, which is causing the fish population to decline.

The Baltic Sea washes nine countries: Latvia, Lithuania, Estonia, Russia, Poland, Germany, Finland, Sweden and Denmark.

The coastline of the sea is 8.000 km. , and the area of ​​the sea is 415.000 sq. km.

It is believed that the sea was formed 14,000 years ago, but in the modern outline of the boundaries there are 4,000 years.

The sea has four bays, the largest Bothnian(washes Sweden and Finland), Finnish(washes Finland, Russia and Estonia), Riga(washes Estonia and Latvia) and freshwater Curonian(washes Russia and Lithuania).

The Baltic Sea washes the shores of the Russian Federation, Denmark, and the Baltic countries. The Russian Federation owns small water areas in the eastern part of the Baltic Sea - the Kaliningrad Bay and part of the Curonian Lagoon (the territory of the Kaliningrad Region) and the eastern outskirts of the Gulf of Finland (the territory of the Leningrad Region).

The Baltic Sea is deeply incised into the northwestern part of Eurasia. This is an inland sea, connected to the North Sea of ​​the Atlantic Ocean by the system of the Øresund (Sund), Great Belt, Small Belt straits, known collectively as the Danish Straits. They pass into the deep and wide straits of the Skagerrak, Kattegat, which already belong to the North Sea, which is directly connected with.

The area of ​​the Baltic Sea is 419 thousand km2, the volume is 21.5 thousand km3, the average depth is 51 m, the greatest depth is 470 m.

About 250 rivers flow into the Baltic Sea. The largest rivers are Vistula, Oder, Neman, Daugava, Neva. The Neva brings the largest amount of water per year - an average of 83.5 km3.
The Baltic Sea stretches from the southwest to the northeast, and its greatest length is 1360 km. The widest point of the sea is at 60° N. sh., between St. Petersburg and Stockholm, it stretches for almost 650 km.

The bottom relief of the Baltic Sea is uneven. The sea lies entirely within the shelf. The bottom of its basin is indented by underwater depressions, separated by hills and socles of islands.

The Baltic Sea is characterized by a long coastline. It has many bays, bays and a large number of islands. The sea is a collection of individual basins: the zone of the Danish Straits, the open or central part of the sea and three large bays - Bothnian, Finnish and Riga, which account for almost half of the sea.

Numerous islands of the Baltic Sea are located both off the mainland coast and in the open sea; in some parts of the sea the islands are grouped in large archipelagos, in others they stand alone.

The largest of the islands: Danish - Zealand, Fyn, Lolland, Falster, Langeland, Mön, Bornholm; Swedish - Gotland, Eland; German - Rügen and Fehmarn; - Saaremaa and Hiiumaa.

The coasts of the northern and southern half of the sea differ sharply in character. The skerry shores of Sweden and Finland are indented with small bays and gulfs, framed by islands composed of crystalline rocks. They are mostly low, sometimes naked, and in some places overgrown with coniferous forest. The southern shores are low-lying, consist of sand and have a large number of shoals. In some places, along the coast, chains of sand dunes stretch here, and long spits protrude into the sea, forming large lagoons desalinated by the flow of rivers. The largest of these shallow bays are Curonian and Vistula.

The bottom sediments of the Baltic Sea are represented mainly by silts and sand. The soils of the Baltic Sea are characterized by stones and boulders, often found at the bottom of the sea. Sandy deposits are common in coastal areas. In the Gulf of Finland, most of the bottom is covered with sands with individual patches of silt, occupying small depressions and forming a field of sediments of the Neva Delta front, somewhat elongated along the strike of the Gulf. The construction of the dam, which fenced off a significant part of the water area from the open sea, significantly changed the composition and distribution of precipitation that existed in natural conditions.

The climate of the Baltic Sea is of maritime temperate latitudes with features of continentality. The peculiar configuration of the sea and a significant length from north to south and from west to east create differences in climatic conditions in different areas of the sea.

The Icelandic low, as well as the Siberian and Azores anticyclones, most significantly affect the weather. The nature of their interaction determines the seasonal features of the weather. In autumn and especially in winter, the Icelandic Low and the Siberian High interact intensively, which intensifies cyclonic activity over the sea. In this regard, in autumn and winter, deep cyclones often pass, which bring with them cloudy weather with strong southwestern and western winds.

In the coldest months - January and February - the average in the central part of the sea is -3°С in the north and -5...-8°С in the east. With rare and short-term intrusions of cold Arctic air associated with the strengthening of the Polar High, the air temperature over the sea drops to –30°С and even to –35°С.

In summer, predominantly western, northwestern weak to moderate winds blow. They are associated with the cool and humid summer weather characteristic of the sea. The average monthly temperature of the warmest month is 14–15°C in the Gulf of Bothnia and 16–18°C in the rest of the sea. Hot weather is rare. It is caused by short-term inflows of warm Mediterranean air.

The temperature conditions of the waters of the Baltic Sea in different parts of it are not the same and depend not only on the geographical location of the place, but also on the meteorological and hydrological features of the area. water. This determines the general picture of the temperature conditions of the sea. In the surface layers, the water temperature varies widely. At depths exceeding 50 meters, the water temperature is kept within 3–4 ° C all year round in the southern part of the sea and near zero in the northern Bothnian region.

During the summer months, surface water temperatures are generally close to air temperatures. Near the eastern shores, the water temperature is higher due to the influence of warm, southward land masses, and along the western, Swedish, shores, it is lower due to the flow of cold waters from the north, from the Gulf of Bothnia. In winter, on the contrary, the eastern parts of the sea are colder than the western ones; they are subject to the influence of the chilled land masses of the mainland, and the western parts of the sea during this period experience a regular influx of warm air masses from the Atlantic.

Limited water exchange with the North Sea and significant river runoff result in low salinity. On the sea surface, it decreases from west to east, which is associated with the predominant inflow of river waters from the eastern Baltic. In the northern and central regions of the basin, salinity somewhat decreases from east to west, since in cyclonic circulation, saline waters are transported from south to northeast along the eastern coast of the sea further than along the western one. A decrease in surface salinity is also traced from south to north in the bays.

Almost throughout the sea, a significant increase in salinity from the surface to the bottom is noticeable. The change in salinity with depth is basically the same throughout the sea, with the exception of the Gulf of Bothnia. In the southwestern and partly central regions of the sea, it gradually and slightly increases from the surface to horizons of 30–50 m; below, between 60–80 m, there is a sharp shock layer (halocline), deeper than which the salinity again slightly increases towards the bottom. In the central and northeastern parts, salinity increases very slowly from the surface to horizons of 70–80 m; deeper, at 80–100 m, there is a halocline, and then salinity slightly increases to the bottom. In the Gulf of Bothnia, salinity increases from the surface to the bottom only by 1–2‰.

In autumn-winter time, the flow of North Sea waters into the Baltic Sea increases, and in summer-autumn it somewhat decreases, which leads to an increase or decrease in the salinity of deep waters, respectively. In the autumn-winter season, the salinity of the upper layers slightly increases due to reduction and deviation during ice formation. In spring and summer, salinity on the surface decreases by 0.2–0.5‰ compared to the cold half of the year. This is explained by the desalination effect of continental runoff and the spring melting of ice. In addition to seasonal fluctuations in salinity, the Baltic Sea, unlike many seas of the World Ocean, is characterized by its significant interannual changes. Salinity variability in the Baltic Sea is one of the most important factors regulating many physical, chemical and biological processes. Due to the low salinity of the surface waters of the sea, their density is also low and decreases from south to north, varying slightly from season to season. Density increases with depth.

The strongest wind waves are observed in autumn and winter in open, deep areas of the sea with prolonged and strong southwestern winds. Stormy 7–8-point winds develop waves up to 5–6 m high and 3–4 m long. The largest waves occur in November. In winter, with stronger winds, the formation of high and long waves is prevented by ice. As in other seas of the northern hemisphere, the surface circulation of the Baltic Sea has a general cyclonic character.

Surface currents are formed in the northern part of the sea as a result of the confluence of waters emerging from the Gulf of Bothnia and the Gulf of Finland. The speed of the permanent currents of the Baltic Sea is very low and is approximately 3–4 cm/s. Sometimes it increases to 10–15 cm/s. The current pattern is very unstable and is often disturbed by the wind. The wind currents prevailing in the sea are especially intense in autumn and winter, and during strong storms their speed can reach 100–150 cm/s.

Deep circulation in the Baltic Sea is determined by the flow of water through the Danish straits. The inlet current in them usually passes to a horizon of 10–15 m. Then this water, being denser, descends into the underlying layers and is slowly transported by the deep current, first to the east and then to the north.

Due to the high degree of isolation from the World Ocean, the tides in the Baltic Sea are almost invisible. Fluctuations in the tidal level at individual points do not exceed 10–20 cm. Two minimums and two maxima are clearly expressed in the seasonal course of the Baltic Sea level. The lowest level is observed in spring. With the arrival of spring flood waters, it gradually rises, reaching a maximum in August or September. After that, the level goes down. The secondary autumn low is coming. With the development of intense cyclonic activity, westerly winds drive water through the straits into the sea, the level rises again and reaches a secondary, but less pronounced maximum in winter. The difference in level heights between the summer maximum and the spring minimum is 22–28 cm. It is larger in bays and smaller in the open sea.

Surge fluctuations in sea level occur quite quickly and reach significant values. In the open areas of the sea, they are approximately 0.5 m, and at the tops of bays and bays they are 1–1.5 and even 2 m. h. Level changes associated with seiches do not exceed 20–30 cm in the open part of the sea and reach 1.5 m in the Neva Bay. Complex seiche level fluctuations are one of the characteristic features of the Baltic Sea regime.

Catastrophic floods are associated with fluctuations in sea level.

The Baltic Sea is covered with ice in some areas. The earliest (around the beginning of November) ice forms in the northeastern part of the Gulf of Bothnia, in small bays and off the coast. Then the shallow areas of the Gulf of Finland begin to freeze. The maximum development of the ice cover reaches in early March. By this time, motionless ice occupies the northern part of the Gulf of Bothnia, the region of the Aland skerries and the eastern part of the Gulf of Finland. Floating ice occurs in the open areas of the northeastern part of the sea.

The main problems of the Baltic Sea are related to the gradual deterioration of oxygen conditions in the deep layers of the sea, which has been observed in recent decades. In some years, oxygen disappears completely already at a depth of 150 m, where it forms hydrogen sulfide. These changes are the result of both natural changes in the environment, mainly temperature, water salinity and water exchange, and anthropogenic impact, which is expressed mainly in an increase in the supply of nutrient salts in the form of various forms of nitrogen and phosphorus.

The significance of the Baltic Sea in the national economy of the countries of the region and the ever-increasing negative impact of anthropogenic factors on the quality of the marine environment require urgent measures to be taken to guarantee the cleanliness of the sea.

Pollution enters the sea directly with sewage or from ships, diffusely through rivers or. The main mass of pollutants is brought into the sea with the flow of rivers (Neva, Vistula) both in a dissolved state and adsorbed on suspension. In addition, the seaside cities, St. Petersburg, Kronstadt, Vyborg and, to the greatest extent, the merchant and military fleets are sources of pollution of the marine environment with oil products.

The greatest harm to the marine environment is caused by toxic substances (salts of heavy metals, DDT, phenols, etc.), oil products, organic and biogenic substances. Every year, about 300 tons of oil products enter the Gulf of Finland from various sources. The main mass of nitrogenous compounds enters the sea diffusely, as well as sulfur compounds, which enter the marine environment mainly through the atmosphere. Toxic substances are discharged mainly by industry. The different nature of pollution complicates the struggle for the purity of the marine environment and requires the implementation of a complex set of water protection measures.

Monitoring of the marine environment is, first of all, the organization of systematic observations of the physicochemical and biological indicators of the marine environment at constant representative points of the reservoir.

The quality of the marine environment of the Baltic Sea as a whole meets the requirements of water users, however, pollution zones have formed near many large cities. It is alarming that over the past decades the content of toxic substances in marine living organisms has increased to two orders of magnitude, which once again indicates the need for urgent water protection measures. Great harm is caused by accidental spills of oil products from tankers. The monitoring results will make it possible to periodically check the state of the marine environment, i.e., to identify the dynamics of marine pollution.

Two small sections of the bottom of the coastal part of the Baltic Sea belonging to Russia are sharply different in terms of geoecological conditions. The most anthropogenic pressure is experienced by the inner, eastern part of the Gulf of Finland within the Leningrad region. The main area of ​​pollution was that part of the bay, which is located east of Kotlin Island, between it and the Neva delta. This happened several years ago after the construction of a dam running from Kotlin Island to the northern and southern mainland shores. An important element of the geoecological situation in the eastern part of the Gulf of Finland are numerous underwater quarries for the extraction of construction raw materials, mainly sand, which in the future may pose a threat to the stability of the coastal part of the bottom and coasts.

The Baltic Sea is the northern marginal body of water in Eurasia. It cuts deep into the land, and due to this it belongs to the water flows of the internal type. The sea fills the waters of the Atlantic. It is located in Northern Europe. The Baltic countries have access to the Baltic Sea. And also such states as: Denmark, Sweden, Finland, Germany, Russia and Poland. The stream connects with the ocean through the system and the North Sea.

The area of ​​the reservoir is about 415 thousand square km. The volume of the water mirror is more than 20 thousand cubic meters. km. The deepest gutter is 470 meters.

Hydrology

The Baltic Sea, whose salinity greatly affects the flora and fauna, is filled with a huge amount of fresh water. Precipitation is their constant source. Salt streams penetrate into the reservoir due to bays and tributaries. The tides have insignificant levels and, as a rule, their magnitude is not more than 20 cm.

Constantly located within a radius of one mark. Air masses can exert a strong influence on it. Near the coast, the water level can rise up to 50 cm, in narrower places - up to 2 meters.

There are practically no storms on the water stream. Like other seas washing Russia, the Baltic reservoir is calm, and rarely when its waves are able to reach a height of 4 meters. Most of all it storms in autumn, in November. Maximum fluctuations - 7-8 points. In winter, they practically stop, this is facilitated by ice.
The constant flow of the Baltic Sea is small. Within 10-15 cm/s. The maximum current increases during storms up to 100-150 cm/s.
The tides of the Baltic Sea are almost imperceptible. This is facilitated by the isolation of the water flow to a greater extent. Their level varies within 20 meters. The maximum increase in water level is in August and September.

A significant part of the coast is covered with ice from October to April. The southern part and the center of the sea, but glaciers can drift along them during the thawing period (June-August).

The Baltic Sea is rich in natural resources. Oil reserves are hidden here, new deposits are being developed. Large deposits of amber have also recently been found. The Nord Stream gas route runs along the bottom of the sea.

And the Baltic Sea is rich in fish and seafood. In recent years, the ecology of the stream has deteriorated significantly. The waters are clogged with toxins coming from large rivers. The presence of dumps of chemical weapons is also recorded.

Due to the shallow depth of the sea, shipping is not very developed here. Only light craft are able to cross the watercourse without problems. The largest ports of the Baltic Sea: Vyborg, Kaliningrad, Gdansk, Copenhagen, Tallinn, St. Petersburg, Stockholm.

The waters of this reservoir are unsuitable for the development of resort tourism, but nevertheless there are sanatoriums and clinics on the coastal part. These are Russian resort cities Svetlogorsk, Zelenogorsk, Sestroretsk, Latvian Jurmala, Lithuanian Neringa, Polish Koszalin and Sopot, German Albek and Binz.

Brief description of water temperature and sea salinity

In the central part of the Baltic Sea, as a rule, the temperature rarely exceeds 15-18 ° C. At the bottom, it is about 4 degrees. The bay often has calm weather and +9..+12 o C.

The Baltic Sea, whose salinity decreases in the direction from west to east, at the beginning of the current has an official indicator of 20 ppm. At depth, this figure increases by 1.5 times.

Name

For the first time, the etymological name "Baltic" is found in a historical treatise of the 11th century. The earlier name of the sea is Varangian. It is it that is mentioned in the famous Tale of Bygone Years.

extreme points

Extreme points of the Baltic Sea:

• southern - Wismar (Germany), coordinates - 53° 45` N. sh.;
• north - Arctic Circle coordinates - 65° 40` s. sh.;
• eastern - St. Petersburg (Russia), coordinates - 30 ° 15` in. d.;
• western - Flensburg (Germany), coordinates - 9 ° 10` in. d.

Geographical characteristics: territory, tributaries and bays

The Baltic Sea (salinity and its characteristics are described below) is extended from the southwest to the northeast for 1360 km. The greatest width is located between the cities of Stockholm and St. Petersburg. It is 650 kilometers.

According to historical data, the Baltic Sea has existed for about 4 thousand years. In the same period of time, the Neva (74 km) begins its existence, which flows into this reservoir. In addition to it, more than 250 rivers merge with the stream. The largest of them are Vistula, Oder, Narva, Neman, Zapadnaya Dvina.

Some ports of the Baltic Sea lie on its large bays. In the north is the Gulf of Bothnia, the largest and deepest. In the east - Riga, located between Estonia and Latvia, Finnish, washing the shores of Finland, Estonia, Russia, and Due to the fact that the latter is separated from the sea by a sandy spit, the water in the stream is almost fresh. This is a unique feature.

The average depth of the Baltic Sea is 50 meters, the bottom is completely within the mainland. This nuance makes it possible to attribute it to inland continental water bodies.

Islands

More than 200 islands of different sizes are located in the sea. They are located unevenly both near the coast and far from them. The largest islands in the Baltic are Zealand, Falster, Mön, Langeland, Lolland, Bornholm, Funen (belong to Denmark); Öland and Gotland (Swedish islands); Fehmarn and Rügen (refers to Germany); Hiiumaa, Saaremaa (Estonia).

Coastline

The Baltic Sea (the ocean strongly affects it with its waters) has a different coastline along the entire perimeter of the waters. In the northern part, the bottom is uneven, rocky, and the coast is indented with small bays, ledges and small islands. The southern part, on the contrary, has a flat bottom, and a low-lying coast, with a sandy beach, which in some areas is represented by small dunes. A frequent occurrence on the young coast is sandy spits, deeply cutting into the sea.
The sedimentary bottom is represented by green, black silt (of glacial origin) and sand, and the soil consists of stones and boulders.

Salinity and its regular changes

Due to the large amount of precipitation and the powerful water flow from the rivers, the Baltic Sea (the salinity of the reservoir is relatively low) is filled with an excess of fresh water. It is distributed unevenly. Where the Baltic reservoir enters deep into the shore, the water is practically fresh, and the North Sea influences its salinity. This position is not permanent. Storm winds contribute to the mixing of water.
Based on this, the salinity of the Baltic Sea is low. A decrease in its level is typical for the coastline, the largest number of ppm is at the bottom.
In the territory where the watercourse meets the straits in the west, the salinity of the waters is up to 20 ‰ on the sea surface, at the bottom - 30 ‰. Off the coast of the Gulf of Bothnia and the Gulf of Finland, the lowest indicator. It does not exceed 3‰. The level from 6 to 8‰ is characteristic of the waters of the central part.

Seasonality also affects the distribution of salinity in the Baltic Sea. So, in the spring-summer season, it decreases by 0.5-0.2 ppm. This is due to the fact that melted rivers carry fresh water to the sea. And in autumn and winter, on the contrary, it increases due to the influx of cold northern masses.

The change in the salinity of the sea is one of the important reasons that regulate the biological, physical and chemical processes on the coast. Partly due to the freshness of the water, the coast has a loose structure.