Baltic Sea coastline. Baltic Sea: depths and relief, description, geographical location

Baltic Sea(Old Russian Varangian, Lith./Lat. Baltijos/Baltijas jūra, Liv. Vālda mer, Est. Läänemeri, Finnish Itämeri, Swiss Östersjön, Dan. Østersøen, German Ostsee, Kashubian Bôłt, Polish Morze Bałtyckie, Bałtyk, Saami Nuortamearra) inland sea of ​​the Atlantic Ocean. It is located off the coast of Northern and Central Europe. It is connected to the North Sea by the Danish Straits. Square- 419 thousand km2, almost equal to the area of ​​the Black Sea (422 thousand km2). The length of the coastline of the Baltic is 7 thousand km. The northernmost point of the Baltic Sea is located near the Arctic Circle, the southernmost point is near Wismar, the westernmost point is in the Flensburg region, and the easternmost point is in the St. Petersburg region. The coast is distributed among the countries as follows: Sweden owns 35% of the coast, Finland - 17%, former USSR had 25% of the coast, Russia now has about 7% (about 500 km). The rest belongs to Lithuania, Latvia, Estonia, Poland, Germany, Denmark.

Dominant Depths 40-100 m, maximum - 470 m. The greatest depths are in the north, off the coast of Sweden, on average 60-150 m. The shallowest is considered Curonian Lagoon where depths do not exceed 5 meters. In some areas there are underwater shoals, which greatly complicates navigation.

From the history of the Baltic Sea
It was formed at the site of a large tectonic trough of the earth's crust during the Alpine era of mountain building at the junction of the Baltic crystalline shield with the sedimentary strata of the Russian Platform. After the melting of the ice sheet, there was an extensive body of water connecting the North Sea with the White Sea. This process began 18-20 thousand years ago. 13 thousand years ago, the glacier finally left the territory of Lithuania. When the ice melted, the water filled the depressions in the Baltic Sea - this is how the cold glacial Baltic Lake was formed, which at different times was connected to the Atlantic Ocean. This lake existed 13-10 thousand years ago.

Somewhat later, the glacier left the Central Swedish lowland. The resulting channel connected the lake with the Atlantic Ocean. With the new arrival of the glacier, the level glacial lake began to rise, and with his departure, he went down by 40 - 50 m. large areas sushi. This is how the Yoldia Sea was formed, which got its name from the abundance of mollusks that lived in it (from lat. Yoldia arctica). The compensatory uplift of the continental plate, which took place in the southern part of the Baltic Sea basin, deprived the Yoldian Sea of ​​communication with the Atlantic Ocean. The rivers have sharply reduced the salinity of this water basin and raised its level. So, 9 thousand years ago, Ancylus Lake was formed (the name comes from the name of the mollusks Ancylus fluviatilis). Its deposits were preserved at a depth of 16-18 m. At this stage of the formation of the Baltic Sea, the climate was warm and dry.

7.5 thousand years ago, the salty waters of the Atlantic Ocean broke into Lake Antsylovo, and the Littorina Sea was formed (the name comes from the name of the mollusks Littorina littoraea). 4 thousand years ago, the Baltic Sea gradually acquired modern look: its salinity has decreased, modern animals and plants begin to predominate.

Salinity
The Baltic Sea is the largest sea in the world with low salt content. Its waters are a mixture of salt water from the ocean and fresh water coming from numerous rivers. The degree of salinity of the sea in different places has indicators that differ from each other, which is due to the weak vertical movement of water layers. If in the southwestern part of the sea it is 8%, in the western part 11%, then in the central water area it is 6%, and in the Gulf of Finland, Riga and Bothnia it barely exceeds 2-3% (cf. the average salinity of the World Ocean is 35%o).

The presence of certain fish species in a particular area is also associated with varying degrees of salinity of the water. The flora and fauna of the Baltic Sea have a transitional character from the sea to freshwater lake. So, often sea shellfish, like oysters, Mua
trunata, Littorina littoralis, etc. are only in the app. parts of the sea where the water is saltier. Along with marine fish, freshwater fish also live in this sea - perch, bream, grayling, whitefish and others. In areas of high salinity and with great depth, cod predominate, different kinds herring, herring, flounder, kalkan, goby, eelpout, sprat. Less often, but still there are salmon - sea trout (trout), whitefish and Baltic salmon (a type of salmon). A lot of three-spined stickleback, small fish. The Aland Islands have seals.

Tidal fluctuations in the Baltic are only a few centimeters. This is due to the fact that the tidal ocean wave, reaching the coast of Denmark, loses its strength by almost 90% or subsides completely. However, the water level in the Baltic Sea changes frequently and abruptly, due to the western and northwestern winds that drive water into the Kaliningrad and Curonian lagoons, as if locking weak river currents in their channels, preventing them from reaching the sea ​​space. If the winds blow from the south and east, the opposite occurs, and in some places the sea moves away from the coast, forming islands of land, interspersed with areas of sandbars. This is also related to fluctuations in water temperatures. In summer, the water temperature is kept in the range from 14° to 20° (sometimes higher, but the average level is 18-19°). warmed up warm water winds that are frequent in these places are driven away from the coast, and bottom, deep currents bring colder layers of water. So in a short time the water temperature can drop to 8-9 °. Summer in the Baltic is not hot, but winter, in turn, is not cold. In winter, the Baltic Sea freezes, but this happens mainly along the coast, where solid ice forms in a small strip or fills the bays, and the Curonian Lagoon freezes earlier than the Kaliningrad Lagoon. It should be noted that the reliability of the ice cover of bays is not the same everywhere, so fishing from such ice is always associated with a certain risk to life. In addition, in some places the ice has large irregularities and has a significant drift speed. Often, cracks and faults can be observed along the coast, especially if windy weather has set in. The heap of ice sometimes takes on bizarre forms, especially if blocks of ice run into rocks or sandbars. Autumn and winter the role of the winds is increasing. South-westerly Atlantic winds carry heat, and long thaws come, accompanied by sleet and rain.
The most dangerous time for fishing is accompanied by strong winds. In a word, the wind is the decisive factor that "makes the weather" throughout the Baltic Sea. Winds in Palanga (Lithuania) have interesting names: maritime(western), predominant in this part of the coast; terrestrial- east wind blowing towards the sea; goat- southeast; Finnish- northwestern. And there is more amber wind(Bernsteinwind - German Bernsteinwind) a weakening north-west wind from the sea on the Baltic coast, which, with sea swell, helps to wash out the so-called amber grass from the exposed amber layers and drives algae with amber to the shore. They flow into the Baltic Sea rivers: Neva, Narva, Western Dvina (Daugava), Venta, Neman, Vistula, Oder. Large islands: Bornholm (Denmark), Gotland, Öland (Sweden), Saaremaa, Hiiumaa (Estonia), Rügen, Usedom (Germany), Alandia. bays: Botanical, Finnish, Riga, Curonian.

Gulf of Riga- a bay in the east of the Baltic Sea between Latvia and Estonia. Partially separated from the rest of the sea by the Estonian island of Ezel (Saaremaa). The most important cities along the coast of the Gulf of Riga are Riga and Pärnu. In the Gulf of Riga is Estonian island Ruhnu. total area: 16300 km², max. length: 174 km, max. width: 137 km, max. depth: 67 m, flowing rivers : Zap. Dvina (Daugava), Courland Aa (Lielupe), Livonian Aa (Gauja), Salis (Salats).Main ports: St. Petersburg, Kaliningrad (Russia), Tallinn (Estonia), Riga, Ventspils, Liepaja (Latvia), Klaipeda (Lithuania), Gdansk-Gdynia, Szczecin (Poland), Rostock, Kiel, Lübeck (Germany), Copenhagen, Malmö , Stockholm, Luleå, Umeå, Gävle, Sundsval, Hudikval (Sweden), Turku, Helsinki, Rauma, Pori, Vaasa, Kokkola (Finland).

Resorts: Pärnu (Estonia), Jurmala, Liepaja, Pavilosta (Latvia), Palanga, Sventoji, Neringa (Lithuania), Kolobrzeg, Ustka (Poland), Heringsdorf, Warnemünde, Binz (Germany), etc.

The Baltic Sea is connected to the North Sea by the Øresund Straits. (Sound), large and small Belts, Kattegat and Skagerrak. Washes the shores of Russia, Estonia, Latvia, Lithuania, Poland, Germany, Denmark, Sweden, Finland.

The maritime boundary of the Baltic Sea runs along the southern entrances of the Øresund straits, the Greater and Lesser Belta. The area is 386 thousand km². The average depth is 71 m. The shores of the Baltic Sea in the south and Yu.-V. predominantly low-lying, sandy, lagoon type; from the land side - dunes covered with forest, from the sea side - sandy and pebble beaches. In the north, the shores are high, rocky, mostly of the skerry type. The coastline is strongly indented, forming numerous bays and coves.

Most large bays: Bothnian (according to physical and geographical conditions, it is the sea), Finnish, Riga, Curonian, Gdansk Bay, Szczecin, etc.

Islands of the Baltic Sea mainland origin. There are many small rocky islets - skerries, located along the northern shores and concentrated in the groups of the Vasi and Aland Islands. The largest islands: Gotland, Bornholm, Sarema, Muhu, Khiuma, Eland, Rügen, etc. It flows into the Baltic Sea a large number of rivers, the largest of which are the Neva, Western Dvina, Neman, Vistula, Odra, etc.

The Baltic Sea is a shallow shelf sea. Depths of 40-100 m predominate. The most shallow water areas are the Kattegat straits. (average depth 28 m), Øresund, large and small belts, the eastern parts of the Gulf of Finland and the Gulf of Bothnia and the Gulf of Riga. These areas of the sea bottom have a leveled accumulative relief and a well-developed cover of loose sediments. Most of the bottom of the Baltic Sea is characterized by a strongly dissected relief, there are relatively deep basins: the Gotland (249 m), Bornholmskaya (96 m), in the Södra-Kvarken Strait (244 m) and the deepest - Landsortsjupet south of Stockholm (459 m). There are numerous stone ridges, ledges are traced in the central part of the sea - continuations of the Cambrian-Ordovician (from north coast Estonia to the northern tip of the island of Öland) and Silurian glints, underwater valleys, glacial-accumulative landforms flooded by the sea.

The Baltic Sea occupies a depression tectonic origin, which is a structural element of the Baltic Shield and its slope. According to modern concepts, the main irregularities of the sea bottom are due to block tectonics and structural denudation processes. The latter, in particular, owe their origin to the underwater ledges of the glints. Northern part The bottom of the sea is composed mainly of Precambrian rocks overlain by a discontinuous cover of glacial and recent marine sediments.

In the central part of the sea, the bottom is composed of Silurian and Devonian rocks, hidden to the south under a layer of glacial and marine sediments of considerable thickness.

The presence of underwater river valleys and the absence of marine sediments under the glacial deposits indicate that in the pre-glacial period there was land on the site of the Baltic Sea. During at least the last ice age, the basin of the Baltic Sea was completely occupied by ice. Only about 13 thousand years ago there was a connection with the ocean, and sea ​​waters filled a hole; formed the Yoldian Sea (for the mollusc Joldia). The phase of the Yoldian Sea is somewhat earlier (15 thousand years ago) preceded by the phase of the Baltic glacial lake, not yet connected with the sea. About 9-7.5 thousand years ago, as a result of tectonic uplift in Central Sweden the connection of the Yoldian Sea with the ocean ceased, and the Baltic Sea again became a lake. This phase of the development of the Baltic Sea is known as Lake Ancylus. (for the mollusc Ancylus). A new land subsidence in the region of the modern Danish straits, which occurred about 7-7.5 thousand years ago, and extensive transgression led to the resumption of communication with the ocean and the formation of the Littorina Sea. The level of the last sea was several meters higher than the modern one, and the salinity was higher. Littorina transgression deposits are widely known on modern coast the Baltic Sea. The secular rise in the northern part of the Baltic Sea basin continues now, reaching 1 m per hundred years in the north of the Gulf of Bothnia and gradually decreasing to the south.

The climate of the Baltic Sea is maritime temperate, strongly influenced by the Atlantic Ocean. It is characterized by relatively small annual temperature fluctuations, frequent precipitation, fairly evenly distributed throughout the year, and fog during the cold and transitional seasons. During the year, westerly winds prevail, which are associated with cyclones coming from the Atlantic Ocean. Cyclonic activity reaches its highest intensity in the autumn-winter months. At this time, cyclones are accompanied by strong winds, frequent storms and cause large rises in water levels off the coast. In the summer months, cyclones weaken and their frequency decreases. The invasion of anticyclones is accompanied by easterly winds.

The stretching of the Baltic Sea by 12° along the meridian determines the noticeable differences climatic conditions its individual regions. average temperature air of the southern part of the Baltic Sea: in January -1.1°C, in July 17.5°C; middle part: in January -2.3°C, in July 16.5°C; Gulf of Finland: in January -5°C, in July 17°C; northern part of the Gulf of Bothnia: in January -10.3°C, in July 15.6°C. Cloudiness in summer about 60%, in winter more than 80%. The average annual rainfall in the north is about 500 mm, in the south over 600 mm, and in some areas up to 1000 mm. The largest number of days with fog falls on the southern and middle parts of the Baltic Sea, where it reaches an average of 59 days a year, the smallest - in the north. Gulf of Bothnia (up to 22 days a year).

The hydrological conditions of the Baltic Sea are determined mainly by its climate, abundance of fresh water and water exchange with the North Sea. An excess of fresh water, equal to 472 km3 per year, is formed due to continental runoff. The amount of water entering in precipitation (172.0 km³ per year) is equal to evaporation. Water exchange with the North Sea averages 1659 km3 per year (salt water 1187 km³ per year, fresh water - 472 km³ per year). Fresh water flows from the Baltic Sea to the North Sea in a runoff current, salty water flows through the straits from the North Sea to the Baltic Sea through the deep current. Strong westerly winds usually cause influx and east winds- the flow of water from the Baltic Sea through all sections of the Øresund straits, the large and small Belts.

The currents of the Baltic Sea form a counter-clockwise circulation. Along the southern coast, the current is directed to the east, along the eastern coast - to the north, along the western coast - to the south, and near the northern coast - to the west. The speed of these currents ranges from 5 to 20 m/sec. Under the influence of winds, currents can change direction and their speed near the coast can reach 80 cm/sec or more, and in the open part - 30 cm/sec.

The surface water temperature in August in the Gulf of Finland is 15°C, 17°C; in the Gulf of Bothnia 9°C, 13°C and in the central part of the sea 14°C, 18°C, and in the south it reaches 20°C. In February - March, the temperature in the open part of the sea is 1°С-3°С, in the Gulf of Bothnia, Finland, Riga and other bays and bays below 0°С. Salinity surface water rapidly decreases with distance from the straits from 11‰ to 6-8‰ (1‰-0.1%) in the central part of the sea. In the Gulf of Bothnia it is 4-5‰ (in the north of the bay 2‰), in the Gulf of Finland 3-6‰ (at the top of the bay 2‰ and less). In the deep and near-bottom water layers, the temperature is 5°C or more, and salinity varies from 16‰ in the west to 12–13‰ in the central part and 10‰ in the north of the sea. In years of increased water inflow, salinity rises to 20‰ in the west, to 14–15‰ in the central part of the sea, and in years of reduced inflow it drops to 11‰ in the middle parts of the sea.

Ice usually appears in early November to the north of the Gulf of Bothnia and reaches its greatest distribution in early March. At this time, a significant part of the Gulf of Riga, the Gulf of Finland and the Gulf of Bothnia is covered with immovable ice. The central part of the sea is usually free of ice.

The amount of ice in the Baltic Sea varies from year to year. In exclusively harsh winters almost the entire sea is covered with ice, in soft ones - only bays. The northern part of the Gulf of Bothnia is covered with ice 210 days a year, the middle part - 185 days; Gulf of Riga - 80-90 days, Danish Straits - 16-45 days.

The level of the Baltic Sea is subject to fluctuations under the influence of changes in wind direction, atmospheric pressure (translational-standing long waves, seiches), inflow river waters and waters of the North Sea. The period of these changes varies from several hours to several days. Rapidly changing cyclones cause level fluctuations of up to 0.5 m or more off the coast of the open sea and up to 1.5-3 m at the tops of bays and bays. Particularly large water rises, which, as a rule, are the result of the superposition of a wind surge on the crest of a long wave, occur in the Neva Bay. The greatest rise in water in Leningrad was noted in November 1824 (about 410 cm) and in September 1924 (369 cm).

Level fluctuations associated with tides are extremely small. The tides have irregular semidiurnal, irregular diurnal and diurnal character. Their size varies from 4 cm (Klaipeda) up to 10 cm (The Gulf of Finland).

The fauna of the Baltic Sea is poor in species, but rich in quantity. The brackish-water race of the Atlantic herring lives in the Baltic Sea (herring), Baltic sprat, as well as cod, flounder, salmon, eel, smelt, vendace, whitefish, perch. From mammals - the Baltic seal. There is an intensive fishery in the Baltic Sea.

Russian hydrographic and cartographic work began in the Gulf of Finland at the beginning of the 18th century. In 1738, F. I. Soimonov published an atlas of the Baltic Sea, compiled from Russian and foreign sources. In the middle of the 18th century many years of research in the Baltic Sea was carried out by A.I. Nagaev, who compiled a detailed sailing position. The first deep-sea hydrological research in the mid-1880s. were performed by S. O. Makarov. Since 1920, hydrological work was carried out by the Hydrographic Department, the State Hydrological Institute, and after Patriotic War From 1941 to 1945, extensive comprehensive research was launched under the direction of the Leningrad branch of the State Oceanographic Institute of the USSR.