Editing Sea of Azov (section)

==Geology and bathymetry==
[[File:AzovseaNASA2.jpg|thumb|Satellite image of Sea of Azov. The shallow Sea of Azov is clearly distinguished from the deeper Black Sea. Numbers: 1. [[Dnieper River]], 2. [[Kakhovka Reservoir]], 3. [[Molochna River]], 4. [[Molochnyi Lyman]], 5. [[Arabat Spit]], 6. [[Syvash]] lagoon system, 7. [[Karkinit Bay]], 8. Kalamitsky Bay, 9. [[Crimea]], 10. Fedosiysky Bay, 11. [[Strait of Kerch]], 12. [[Black Sea]], 13. Sea of Azov, 14. [[Don River (Russia)]], 15. [[Taganrog Bay]], 16. Yeysk Liman, 17. Beisug Liman]]
The [[International Hydrographic Organization]] defines the limit of the Sea of Azov in the [[Strait of Kerch|Kertch Strait]] {{sic}} as "The limit of the [[Black Sea]]", which is itself defined as "A line joining Cape Takil and Cape Panaghia (45°02'N)".<ref>{{cite web|url=https://iho.int/uploads/user/pubs/standards/s-23/S-23_Ed3_1953_EN.pdf|title=Limits of Oceans and Seas, 3rd edition|year=1953|publisher=International Hydrographic Organization|access-date=28 December 2020|archive-url=https://web.archive.org/web/20111008191433/http://www.iho-ohi.net/iho_pubs/standard/S-23/S23_1953.pdf|archive-date=October 8, 2011}}</ref>

The sea is considered an internal sea of Russia and Ukraine, and its use is governed by an agreement between these countries ratified in 2003.<ref>[https://web.archive.org/web/20081009023750/http://2004.kremlin.ru/events/articles/2003/12/57621/58572.shtml Treaty between the Russian Federation and Ukraine on cooperation in the use of the Sea of Azov and Kerch Strait], December 24, 2003, kremlin.ru {{in lang|ru}}</ref>
The sea is {{convert|360|km}} long and {{convert|180|km}} wide and has an area of {{convert|39000|km2}}; it is the smallest sea within the countries of the former Soviet Union.<ref name=kki>{{cite book |last=Kapitonov |first=V. I. Borisov and E. I. |language=ru |url=http://azov.tv/azovsea.html |publisher=KKI |year=1973 |title=Sea of Azov |url-status=dead |archive-url=https://web.archive.org/web/20100917112747/http://azov.tv/azovsea.html |archive-date=2010-09-17 }}</ref> The main rivers flowing into it are the [[Don River, Russia|Don]] and [[Kuban River|Kuban]]; they ensure that the waters of the sea have comparatively low salinity and are almost fresh in places, and also bring in huge volumes of [[silt]] and sand. Accumulation of sand and shells results in a smooth and low coastline, as well as in numerous spits and sandbanks.<ref name=bse1/>

The Sea of Azov is the shallowest sea in the world with an average depth of {{convert|7|m}} and maximum depth of {{convert|14|m}};<ref name=k65/> in the bays, where silt has built up, the average depth is about {{convert|1|m|ft|0}}. The sea bottom is also relatively flat with the depth gradually increasing from the coast to the centre.<ref name=seas>{{cite book |last=Zalogin |first=A. D. Dobrovolsky and B. S. |language=ru |title=Seas of USSR |publisher=Moscow University |year=1982}}</ref> The Sea of Azov is an internal sea with passage to the Atlantic Ocean going through the Black, [[Sea of Marmara|Marmara]], [[Aegean Sea|Aegean]] and Mediterranean seas. It is connected to the Black Sea by the Strait of Kerch, which at its narrowest has a width of {{convert|4|km}} and a maximum depth of {{convert|15|m|ft|0}}.<ref name=k65/> The narrowness of the Kerch Strait limits the water exchange with the Black Sea. As a result, the salinity of the Sea of Azov is low; in the open sea it is 10–12 on the [[Practical Salinity Unit|Practical Salinity Scale]] (PSS), about one third of the salinity of the oceans; it is even lower (2–7 (PSS)) in the Taganrog Bay at the northeast end of the Sea. The long-term variations of salinity on the PSS are low, and are mostly caused by changes in humidity and precipitation.<ref>Kostianoy, pp. 69–73</ref><ref>{{cite web|url=http://www.nodc.noaa.gov/OC5/AZOV2006/HTML/s_climatology.html|title=Climatological Atlas of the Sea of Azov|publisher=National Oceanographic Data Centre|access-date=2008-01-06}}</ref>

Although more than 20 rivers flow into the sea, mostly from the north,<ref name=seas/> two of them, the [[Don River (Russia)|Don]] and [[Kuban River|Kuban]] rivers, account for more than 90% of water inflow. The contribution of the Don is about twice that of the Kuban.<ref name=seas/> The Kuban delta is located at the southeast, on the east side of the Kerch Strait. It is over 100&nbsp;km long and covers a vast flooded area with numerous channels. Because of the spread, the delta has low contrast in satellite images, and is hardly visible in the map. The Don flows from the north into the large [[Taganrog Bay]]. The depth there varies between 2 and 9 metres, while the maximum depth is observed in the middle of the sea.<ref name=k66/>

Typical values of the annual inflow and outflow of water to the sea, averaged over the period from 1923 to 1985, are as follows: river inflow 38.6&nbsp;km<sup>3</sup>, precipitation 15.5&nbsp;km<sup>3</sup>, evaporation 34.6&nbsp;km<sup>3</sup>, inflow from the Black Sea 36–38&nbsp;km<sup>3</sup>, outflow 53–55&nbsp;km<sup>3</sup>.<ref name=k67/> Thus, about 17&nbsp;km<sup>3</sup> of fresh water is outflowing from the Azov Sea to the Black Sea.<ref name=bse1/> The depth of Azov Sea is decreasing, mostly due to the river-induced deposits.<ref name=kki/> Whereas the past hydrological expeditions recorded depths of up to 16 metres, more recent ones could not find places deeper than 13.5–14 metres.<ref name=kki/> This might explain the variation in the maximum depths among different sources. The water level fluctuates by some 20&nbsp;cm over the year due to the snow melts in spring.<ref name=k67>Kostianoy, p. 67</ref>

The [[Taman Peninsula]] has about 25 [[mud volcano]]es, most of which are active. Their eruptions are usually quiet, spilling out mud, and such gases as methane, carbon dioxide and [[hydrogen sulfide]], but are sometimes violent and resemble regular volcanic eruptions. Some of those volcanoes are under water, near the shores of the peninsula. A major eruption on 6 September 1799, near Golubitskaya [[stanitsa]], lasted about 2 hours and formed a mud island 100 metres in diameter and 2 metres in height; the island was then washed away by the sea. There were similar eruptions in 1862, 1906, 1924, 1950 and 1952.<ref name=kki/>

The current vertical profile of the Sea of Azov exhibits oxygenated surface waters and [[Anoxic waters|anoxic]] bottom waters, with the anoxic waters forming in a layer {{convert|0.5|to(-)|4|m|ft|0}} in thickness. The occurrence of the anoxic layer is attributed to seasonal eutrophication events associated with increased sedimentary input from the Don and Kuban Rivers. This sedimentary input stimulates biotic activity in the surface layers, in which organisms photosynthesise under aerobic conditions. Once the organisms expire, the dead organic matter sinks to the bottom of the sea where bacteria and microorganisms, using all available oxygen, consume the organic matter, leading to anoxic conditions. Studies have shown that in the Sea of Azov, the exact vertical structure is dependent on wind strength and [[sea surface temperature]], but typically a 'stagnation zone' lies between the oxic and anoxic layers.<ref>{{cite journal |last1=Debolskaya |first1=E. I. |first2=E.V. |last2=Yakusheva |first3=I.S. |last3=Kuznetsov |title=Analysis of the hydrophysical structure of the Sea of Azov in the period of the bottom anoxia development |doi=10.1016/j.jmarsys.2007.02.027 |journal=Journal of Marine Systems |volume=70 |page=300 |year=2008 |issue=3–4|bibcode=2008JMS....70..300D }}</ref>