The Black Sea. Odessa in Ukraine

Geologists consider, that tens millions years ago on seat of the modern Mediterranean, Black, Azov, Caspian and Aral seas there was a gulf of the most ancient huge ocean Tetis. By long evolution this gulf one step at a time was splitted up, and, finally, about one million years ago, as a result of formation Caucasian and Crimean mountains Black sea has stood apart in closed, almost fresh reservoir.

Eight thousand years ago, possibly, after the strongest earthquake, the passage Bosporus was formed, and salty Mediterranean waters began to mix up with the Black Sea. More than 300 rivers and rivulets bear the fresh waters in the sea, the largest — Danube, Dnestr, Southern Bug, Dnepr.

The Black Sea is located inside of the Euroasian continent and borrows the area in 423 thousand square kilometers. The general extent of a coastal line makes 4340 km, from it of 475 km are in Russia.

The Black Sea has almost ocean blue and a transparency on depth up to 25 m, and in depths, as well as at oceans; there is an eternal gloom.

The Black Sea has divisions on depth on two zones — oxygen (up to depth 150–200) and deprived lives hydrosulphuric (depths below 200), which borrows 87 % of its water weight.

The density of water with depth increases, and its all weight is in a stagnant condition, water exchange is insignificant, there is no oxygen, seaweed and living beings, except for bacteria microspira. Living in a plenty in depth of the sea, they decompose corpses of animals and plants. As a result of their activity hydrogen sulphide, which collects at the bottom is allocated.

It is considered, that for millions years of a bacterium have saved up in the sea more than billion tons of hydrogen sulphide. Hydrogen sulphide — poisonous gas besides it can burn and blow up. Nevertheless, threat of explosion to Black Sea does not threaten, as the percent of concentration of hydrogen sulphide is too small for achievement of such effect.

So only flora and fauna populate the top layer of the sea making about 13 % from the general volume of water. Hydro biologists total in it hardly more than 250 types of seaweed and about 2 thousand types of alive organisms.

In The Black Sea salinity of water on a surface averages 18,5 g/l, at coasts it is usual a little bit less, however on Anapa shoaliness average salinity reaches 18,7 g/l. The Black Sea water twice less salty, than water in the World ocean where the level of salts makes 35–36 g/l.

Lower salinity in Black sea in comparison with ocean speaks greater delivery of fresh waters from the rivers, as well as a drain of water from the Sea of Azov with lower mineralization. Fresh waters too contain salts, however in very small quantities so, in thirty liters of rain (fresh) water the quantity of salts is made with only 1. On what color of water in the sea depends? The some people think, that from color of the sky. It not at all so. Color of water depends on how marine water and its impurity disseminate sunlight. The more in water of impurity, sand and other weighed particles, the green water. The water more salty and is purer, it dark blue. The large rivers, which freshen water run into Black sea many and bear with itself many various suspensions, therefore water in it — more likely green-dark blue, and at coast — more green with various shades emerald.

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