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Encyclopedia Britannica - Main :: BER-BLA |
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BLACK SEA (or EUxINE; anc. Pontus Euxinus ) ,i a body
coast
Asia
Minor . The northern boundary is broken at Kertch by a strait entering into the Sea of Azov
fathom
south
east
Trebizond
great
The depths of the Black Sea are lifeless, higher organic life not being known to exist below Too fathoms. Fossiliferous remains of Dreissena, Cardium and other molluscs have, however, been dredged up, which help to show that conditions formerly existed in the Black Sea similar to those that exist at the present day in the Caspian Sea. According to N. Andrusov, when the union of the Black Sea with the Mediterranean through the Bosporus took place, salt water rushed into it along the bottom of the Bosporus and killed the fauna of the less saline waters. This gave rise to a production of sulphuretted hydrogen which is found in the deposits, as well as in the deeper waters. Observations in temperature and salinity have only been taken during summer. During summer the surface salinity of the Black Sea is from 1.70 to 2.00 % down to 50 fathoms, whereas in the greater depths it attains a salinity of 2.25%. The temperature is rather remarkable, there being an intermediate cold layer between 25 and 50 fathoms. This is due to the sinking of the cold surface water (which in winter reaches freezing-point) on to the top of the denser more saline water of the greater depths. There is thus a minimum circulation in the greater depths causing there uniformity of temperature, an absence of the circulation of oxygen by other means than diffusion, and a protection of the sulphuretted hydrogen from the oxidation which takes place in homologous situations in the open ocean. The temperature down to 25 fathoms is from 78.3 to 46.2 F., and in the cold layer, between 25 and 5o fathoms, is from 46.2 to 43.5 F., rising again in greater depths to 48.2 F. The Sea of Marmora may be looked upon as an arm of the Aegean Sea and thus part of the Mediterranean proper. Its salinity is comparable to that of the eastern basin of the Mediterranean, which is greater than that of the Black Sea, viz. 4 %. Similar currents exist in the Bosporus to those of the Strait of Gibraltar. Water of less salinity flows outwards from the Black Sea as an upper current, and water of greater salinity from the Sea of Marmora flows into the Black Sea as an under-current. This under-current flows towards CapeTarhangut, where it divides into a left and right branch. The left branch is appreciably noticed near Odessa and the north-west corner; the right branch sweeps past the Crimea, strikes the Caucasian shore (where it comes to the surface running across, but not into, the south
east
coast
Asia
Minor between Cape Jason andi The early Greek navigators gave it the epithet of axenus, i.e. unfriendly to `strangers, but as Greek colonies sprang up on the shores this was changed to euxinus, friendly to strangers.2'5 Sinope. This current causes a warmer climate where it strikes. So marked is this current that it has to be taken into account in the navigation of the Black Sea. The Sea of Azov
See N. Andrusov, " Physical Exploration of the Black Sea," in Geographical Journal, vol. i. p. 49. End of Article: BLACK SEA (or EUxINE; anc. Pontus Euxinus ) If you wish, you can link directly to this article.
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