Black Sea

Black Sea

This entry is compiled and applied by "popular science China" Science Encyclopedia

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The Black Sea is an inland sea between Europe and Asia. It is inland and overflowed by the narrow Bosporus Strait, covering an area of about 424000 square kilometers.

The Black Sea is connected with the Mediterranean Sea through the Turkish Strait. The important rivers flowing into the Black Sea are the Danube and Dnieper. The coastal countries are Turkey, Bulgaria, Romania, Ukraine, Russia and Georgia. Important coastal cities include Sochi, Istanbul, Burgas, Varna, konstanza, turcha, Odessa, Sevastopol, Batumi, etc.

geographical position

The intercontinental sea between Southeast Europe and the peninsula of Asia Minor is named for its dark and stormy waters. The Black Sea is connected with the Mediterranean Sea through the Bosporus Strait, the Marmara Sea and the Dardanelles Strait to the west, and the Azov Sea through the Kerch Strait to the north. The Black Sea is oval in shape, with a maximum length of 1150 km from east to west, a maximum width of 611 km from north to south, and a minimum width of 263 km from central China, covering an area of 422000 square kilometers and a coastline of about 3400 km. The average water depth is 1315m and the maximum water depth is 2210m. Ukraine is on the north coast, Russia is on the northeast coast, Georgia is on the east coast, Turkey is on the south coast, Bulgaria and Romania are on the west coast.

The Strait of Black Sea is located between the Asian part and the European part of Turkish territory. It is an important route connecting Europe, the subcontinent, the Black Sea and the Mediterranean Sea. The Black Sea Strait is composed of Bosphorus Strait, Marmara Sea and Dardanelle Strait, with a total length of 375 km. The Bosporus Strait is about 30 km long and the Dardanelle Strait is 65 km long. The average depth of the Bosporus and Dardanelle Straits is 40-100 meters. The central part of the Marmara Sea covers an area of 11000km2 and the deepest part is 1355m. Bosporus Strait is the narrowest section of the Strait, only about 700 meters wide.

Because the salt content of the Black Sea is less than that of the Mediterranean Sea, there is a special water exchange phenomenon, that is, the surface water of 10-20 meters flows to the Mediterranean Sea, and the bottom water flows to the Black Sea. The Strait is navigable all year round. As the Black Sea Strait is of great significance in both economic and military strategy, it was once the target of great powers.

Coastal countries

The coastal countries are Romania, Turkey, Bulgaria, Ukraine, Russia and Georgia. Important coastal cities include Istanbul, Burgas, Varna, konstanza, turcha, Odessa, Sevastopol, Batumi, etc.

Flow path

The Black Sea is connected with the distant Atlantic Ocean through the Bosporus Strait, sea of Marmara, Dardanelle Strait, Aegean Sea and Mediterranean Sea in its southwest corner. Crimea Peninsula extends into the Black Sea from the north, and the narrow Kerch Strait in the East leads to the smaller Azov Sea. The surface of the Black Sea is about 461000 square kilometers (178000 square miles), and the deepest is 2210 meters (7250 feet). There are few lowlands on the Black Sea coast, and most of them are on the north coast. The major rivers flowing into the Black Sea are the Danube, the nieber, the Nestor and the Don. It was originally a remnant basin of the ancient Mediterranean Sea. Today's shape could have been 58 million years ago. At that time, the crust of ancient Anatolia rose, and the sea basin was separated from the Mediterranean Sea; the newly formed Black Sea basin was gradually separated from the ocean, its salt content decreased, and then slowly separated from the sea area. The salt content of the Black Sea is almost half of that of the world's oceans.

hydrographic features

The annual precipitation in the Black Sea area is 600-800 mm, and the runoff of some large rivers in Europe is collected. The annual average water inflow to the sea is 35.5 billion cubic meters (of which the Danube River accounts for 60%). The total amount of fresh water is far more than the sea surface evaporation, desalinating the salt content of the surface water, making the average salinity only 12-22 ‰. The salinity of the surface layer is small, and the density leap layer is formed between the upper and lower layers, which seriously prevents the exchange of the upper and lower layers, and the deep seawater is seriously anoxic.

Through the action of anaerobic bacteria, sulfate in seawater is decomposed to form highly toxic hydrogen sulfide, which is toxic to fish. The Black Sea is also the only double sea on earth. The upper surface of the Black Sea produces a large number of sturgeon, mackerel and mackerel. By the late 20th century, industrial and urban waste from the Danube River, the nieber River and other rivers flowing into the Black Sea had increased the pollution layer of the sea water and reduced the number of fish in the sea.

The Black Sea is a large and anoxic ocean system. According to the observation, there is no oxygen in the water layer below 220 meters. In the absence of oxygen and organic matter, sulfate in seawater is decomposed to form hydrogen sulfide under the action of special bacteria. Hydrogen sulfide is toxic to fish. Therefore, in addition to some marine animals and plants in the marginal shallow sea area and the upper layer of the sea, the deep sea area and the seabed are almost a dead world. At the same time, hydrogen sulfide is black, which makes the deep seawater black. The income of fresh water in the Black Sea is greater than the evaporation of sea water, which makes the sea surface of the Black Sea higher than that of the Mediterranean Sea. The sea water with lower salinity flows from the surface of the Strait to the Mediterranean Sea. The sea water with higher salinity in the Mediterranean Sea flows into the Black Sea from the lower part of the Strait. Because the Strait is shallow, the water inflow into the Black Sea is hindered, so that the water inflow into the Black Sea is less than the water outflow from the Black Sea, which maintains the growth of the black sea water dynamic equilibrium.

Climatic characteristics

In January, the average temperature of the central part of the Black Sea is 8 ℃ (46 ° f), and that of the western part is 2-3 ℃ (36-37 ° f). In spring, the average temperature of the whole region is 16 ℃ (61 ° f), and it rises to 24 ℃ (75 ° f) in summer. In winter, the absolute lowest temperature in the northwest reaches - 30 ℃ (- 22 ° f). In winter, the surface water temperature is - 0.5 ℃ (31 ° f), the middle layer is 6 ℃ (43 ° f), and the bottom layer is 9.1 ℃ (48.4 ° f); in summer, the surface water temperature is 26 ℃ (79 ° f), the middle layer is 7 ℃ (45 ° f), and the bottom layer is still 9.1 ℃ (48.4 ° f).

In winter, the northerly gale prevails in the Black Sea, and the cold polar air is constantly attacking. The Black Sea, especially in the northwest sea area, is a spectacular scene, which has become a major feature of the Black Sea. The strong cold air also drops rapidly along some mountain passes and passes, and the wind speed can reach 20-40 M / s, forming a rare strong wind, which is called Bula wind.

Characteristics of sea quality

The Black Sea is one of the deepest inland seas in the world. The black sea itself is very deep. The water flowing into the Black Sea from rivers and the Mediterranean Sea is relatively low in salinity, so it is relatively light. They float on the water with high salinity. In this way, there is no communication between deep water and shallow water. The junction of the two layers of water is between 100 and 150 meters deep. It takes thousands of years for the two layers of water to completely communicate with each other. The oxygen consumed in the decomposition of biological bodies on the sea floor is not replenished. In this environment of severe hypoxia, only anaerobes can survive. Their metabolism releases carbon dioxide and toxic hydrogen sulfide (H < sub2 < / Subs). Other organisms can actually only live in water above 200 meters deep.

The Black Sea is a remnant basin of the ancient Mediterranean Sea. At the end of the Paleocene, Asia Minor uplifted. The Black Sea separated from the Mediterranean Sea and gradually formed the inner sea. 25 million years ago, the black sea was connected to the Mediterranean. With the crustal movement and glaciation, the Black Sea and the Mediterranean Sea were repeatedly isolated and connected, and formed a connection after the great glaciation 6000-8000 years ago.

natural resources

ocean resources

The black sea covers an area of 420300km ~ 2 and is 1180km long from east to west. From the southern margin of Crimea Peninsula to the coast of black Hainan, the Black Sea mountains are slightly flat near the Bosporus Strait on the West Bank. The istranja mountain is in the southwest corner, and the Danube River Delta is in the north. The northwest and north coasts are low-lying. Only the southern Crimea mountains form steep cliffs along the coast. The area of coastal continental shelf only accounts for 25% of the total water area, and reaches the submarine basin through the continental slope, accounting for 25% of the total water area. The bottom of the basin is flat and gradually deepens to the center, with the deepest depth more than 2200m.

The average depth of the Black Sea is 1271 meters, and the upper layer is from the surface to the depth of 200 meters. Below 200 meters is the lower layer, because there is a lot of hydrogen sulfide in the sea water, and there are few organisms.

Natural gas resources

The area of gas hydrate in the Black Sea basin is about 28180.8 million square kilometers, accounting for 6815% of the total area of the Black Sea (421.08 million square kilometers). 90% of the deep water area has hydrate formation. The total area of natural gas hydrate in the seabed (including the continental shelf of 2915276km2) is 2915080000km2.

The thickness of the gas hydrate stable zone in the Black Sea varies with the depth of the seabed. The greater the depth of the seabed, the greater the thickness of the gas hydrate stable zone, and vice versa. The depth of the seafloor is less than 1 km, and the gas hydrate stable zone is thick

Chinese PinYin : Hei Hai