Editing Lake Baikal (section)

==Geography and hydrography==
[[File:Yeniseirivermap.png|thumb|265px|upright=1.25|The [[Yenisey]] basin, which includes Lake Baikal]]

Lake Baikal is in a [[rift valley]], created by the [[Baikal Rift Zone]], where the Earth's crust is slowly pulling apart.<ref name="oddities">{{cite web|url=http://www.gi.alaska.edu/ScienceForum/ASF9/986.html|title=The Oddities of Lake Baikal|publisher=Alaska Science Forum|access-date=7 January 2007|archive-url=https://web.archive.org/web/20070203174400/http://www.gi.alaska.edu/ScienceForum/ASF9/986.html|archive-date=3 February 2007}}</ref> At {{convert|636|km|abbr=on}} long and {{convert|79|km|abbr=on}} wide, Lake Baikal has the largest surface area of any freshwater lake in Asia, at {{convert|31722|km2|abbr=on}}, and is the deepest lake in the world at {{convert|1642|m|ft fathom|abbr=off}}. The surface of the lake is {{convert|455.5|m|0|abbr=on}} above sea level, while the bottom of the lake is {{convert|1186.5|m|ft fathom|abbr=on}} below sea level, and below this lies some {{convert|7|km|abbr=on}} of [[sediment]], placing the rift floor some {{convert|8|-|11|km|abbr=on}} below the surface, the deepest continental [[rift]] on Earth.<ref name="oddities"/>

In geological terms, the rift is young and active – it widens about 4&nbsp;mm (0.16&nbsp;in) per year.<ref name="earthquake insight">{{cite web |last1=HUBBARD AND BRADLEY |title=M5.4 earthquake below Lake Baikal |url=https://earthquakeinsights.substack.com/p/m54-earthquake-below-lake-baikal |website=Earthquake Insights |date=16 January 2024 |access-date=Jan 16, 2024}}</ref> The fault zone is also seismically active; hot springs occur in the area and notable [[earthquake]]s happen every few years. The lake is divided into three basins: North, Central, and South, with depths about {{convert|900|m|abbr=on}}, {{convert|1600|m|abbr=on}}, and {{convert|1400|m|abbr=on}}, respectively. Fault-controlled accommodation zones rising to depths about {{convert|300|m|abbr=on}} separate the basins. The North and Central basins are separated by [[Academician Ridge]], while the area around the Selenga Delta and the Buguldeika Saddle separates the Central and South basins. The lake drains into the [[Angara]], a tributary of the [[Yenisey]]. Landforms include [[Cape Ryty]] on Baikal's northwest coast.

Baikal's age is estimated at 25–30&nbsp;million years, making it the most [[ancient lake]] in [[geology|geological]] history.<ref name="unesco"/><ref name=ScienceDaily2017/> It is unique among large, high-latitude lakes, as its sediments have not been scoured by overriding continental ice sheets. Russian, U.S., and Japanese cooperative studies of deep-drilling [[Core sample|core sediments]] in the 1990s provide a detailed record of climatic variation over the past 6.7&nbsp;million years.<ref>Kravchinsky, V.A., M.A. Krainov, M.E. Evans, J.A. Peck, J.W. King, M.I. Kuzmin, H. Sakai, T. Kawai, and D. Williams. Magnetic record of Lake Baikal sediments: chronological and paleoclimatic implication for the last 6.7 Myr. Palaeogeography, Palaeoclimatology, Palaeoecology, 195, 281–298, 2003. {{doi|10.1016/S0031-0182(03)00362-6}}</ref><ref>Kravchinsky, V.A., M.E. Evans, J.A. Peck, H. Sakai, M.A. Krainov, J.W. King, M.I. Kuzmin. A 640kyr geomagnetic and paleoclimatic record from Lake Baikal sediments. Geophysical Journal International, 170 (1), 101–116, {{doi|10.1111/j.1365-246X.2007.03411.x}}, 2007.</ref>

Longer and deeper sediment cores are expected in the near future.{{update inline|date=May 2023}} Lake Baikal is the only confined freshwater lake in which direct and indirect evidence of [[gas hydrate]]s exists.<ref>M.I. Kuzmin ''et al.'' (1998). First find of gas hydrates in sediments of Lake Baikal. Doklady Adademii Nauk, 362: 541–543 (in Russian).</ref><ref>{{cite journal |author1=M. Vanneste |author2=M. De Batist |author3=A. Golmshtok |author4=A. Kremlev |author5=W. Versteeg |year=2001 |title=Multi-frequency seismic study of gas hydrate-bearing sediments in Lake Baikal, Siberia |journal=[[Marine Geology (journal)|Marine Geology]] |volume=172 |issue=1 |pages=1–21 |doi=10.1016/S0025-3227(00)00117-1|bibcode=2001MGeol.172....1V }}</ref><ref>{{cite journal |author1=P. Van Rensbergen |author2=M. De Batist |author3=J. Klerkx |author4=R. Hus |author5=J. Poort |author6=M. Vanneste |author7=N. Granin |author8=O. Khlystov |author9=P. Krinitsky |year=2002 |title=Sublacustrine mud volcanoes and methane seeps caused by dissociation of gas hydrates in Lake Baikal |journal=[[Geology (journal)|Geology]] |volume=30 |issue=7 |pages=631–634 |doi=10.1130/0091-7613(2002)030<0631:SMVAMS>2.0.CO;2|url=http://www.gt-crust.ru/jour/article/view/478 |bibcode=2002Geo....30..631V }}</ref>

The lake is surrounded by mountains; the [[Baikal Mountains]] on the north shore, the [[Barguzin Range]] on the northeastern shore and the [[Primorsky Range]] stretching along the western shore. The mountains and the [[taiga]] are protected as a national park. It contains 27 islands; the largest, [[Olkhon]], is {{convert|72|km|abbr=on}} long and is the third-largest lake-bound island in the world. The lake is fed by as many as 330 inflowing rivers.<ref name="cnn">{{cite news|url=http://www.cnn.com/SPECIALS/2000/russia/story/train/lake.baikal/|title=Lake Baikal: the great blue eye of Siberia|publisher=CNN |access-date=21 October 2006 |archive-url = https://web.archive.org/web/20061011114225/http://www.cnn.com/SPECIALS/2000/russia/story/train/lake.baikal/ <!-- Bot retrieved archive --> |archive-date = 11 October 2006}}</ref> The main ones draining directly into Baikal are the [[Selenga]], the [[Barguzin (river)|Barguzin]], the [[Upper Angara]], the [[Turka (Lake Baikal)|Turka]], the [[Sarma (river)|Sarma]], and the [[Snezhnaya]]. It is drained through a single outlet, the [[Angara]].

Regular winds exist in Baikal's rift valley.<ref>{{Citation|last=Touchart|first=Laurent|title=Baikal, Lake|date=2012|encyclopedia=Encyclopedia of Lakes and Reservoirs|series=Encyclopedia of Earth Sciences Series|pages=83–91|editor-last=Bengtsson|editor-first=Lars|place=Dordrecht|publisher=Springer Netherlands|language=en|doi=10.1007/978-1-4020-4410-6_50|isbn=978-1-4020-4410-6|editor2-last=Herschy|editor2-first=Reginald W.|editor3-last=Fairbridge|editor3-first=Rhodes W.}}</ref>

===Water characteristics===
[[File:Baikal 1739.jpg|thumb|Lake Baikal's water is especially clear]]
Baikal is one of the clearest lakes in the world.<ref name=Jung2004/> During the winter, the water transparency in open sections can be as much as {{convert|30-40|m|ft|abbr=on|-1}}, but during the summer it is typically {{cvt|5–8|m|ft|round=5}}.<ref name=FEOW>Freshwater Ecoregions of the World (2008). ''[http://www.feow.org/ecoregions/details/lake_baikal Lake Baikal.] {{Webarchive|url=https://web.archive.org/web/20160303193643/http://www.feow.org/ecoregions/details/lake_baikal |date=3 March 2016 }}'' Retrieved 16 July 2014.</ref> Baikal is rich in oxygen, even in deep sections,<ref name=FEOW/> which separates it from distinctly [[Stratification (water)|stratified]] bodies of water such as [[Lake Tanganyika]] and the [[Black Sea]].<ref>{{cite book | author1=Hutter| author2=Yongqi | author3=Chubarenko | year=2011 | title=Physics of Lakes: Foundation of the Mathematical and Physical Background | volume=1 | page=11 | publisher=Springer | isbn=978-3-642-15178-1}}</ref><ref>{{cite web| title=Unique body of water | url=http://www.blackseascene.net/content/content.asp?menu=0040032_000000 | publisher=Black Sea Scene | access-date=5 March 2018}}</ref>

In Lake Baikal, the water temperature varies significantly depending on location, depth, and time of the year. During the winter and spring, the surface freezes for about 4–5 months; from early January to early May–June (latest in the north), the lake surface is covered in ice.<ref name=baikalice>{{cite web| title=Ice Conditions | url=http://www.bww.irk.ru/baikalclimate/baikalice.html | publisher=bww.irk.ru | access-date=8 June 2017}}</ref> On average, the ice reaches a thickness of {{convert|0.5|to(-)|1.4|m|ft|abbr=on}},<ref>{{cite web| title=Baikal seal | url=http://baikal.ru/en/baikal/excursion/nerpa.html | publisher=baikal.ru | access-date=9 June 2017}}</ref> but in some places with [[hummock]]s, it can be more than {{convert|2|m|ft|abbr=on}}.<ref name=baikalice/> During this period, the temperature slowly increases with depth in the lake, being coldest near the ice-covered surface at around freezing, and reaching about {{convert|3.5-3.8|C|F|abbr=on}} at a depth of {{convert|200-250|m|ft|abbr=on}}.<ref name=Gurulev>{{cite web| author=Gurulev, S.A. | title=Temperature of Lake Baikal Water | url=http://www.bww.irk.ru/baikalwater/temperature.html | publisher=bww.irk.ru | access-date=8 June 2017}}</ref> After the surface ice breaks up, the surface water is slowly warmed up by the sun, and in May–June, the upper {{convert|300|m|ft|abbr=on}} or so becomes homothermic (same temperature throughout) at around {{convert|4|C|F|abbr=on}} because of water mixing.<ref name=FEOW/><ref name=Gurulev/> The sun continues to heat up the surface layer, and at the peak in August can reach up to about {{convert|16|C|F|abbr=on}} in the main sections<ref name=Gurulev/> and {{convert|20-24|C|F|abbr=on}} in shallow bays in the southern half of the lake.<ref name=FEOW/><ref name=Pomazkina2012>{{cite journal|author1=Pomazkina, G. |author2=L. Kravtsova |author3=E. Sorokovikova | title=Structure of epiphyton communities on Lake Baikal submerged macrophytes | year=2012 | journal=Limnological Review | volume=12 | issue=1 | pages=19–27 | doi=10.2478/v10194-011-0041-1| doi-access=free }}</ref> During this time, the pattern is inverted compared to the winter and spring, as the water temperature falls with increasing depth. As the autumn begins, the surface temperature falls again and a second homothermic period at around {{convert|4|C|F|abbr=on}} of the upper circa {{convert|300|m|ft|abbr=on}} occurs in October–November.<ref name=FEOW/><ref name=Gurulev/> In the deepest parts of the lake, from about {{convert|300|m|ft|abbr=on}}, the temperature is stable at {{convert|3.1-3.4|C|F|abbr=on}} with only minor annual variations.<ref name=Gurulev/>

The average surface temperature has risen by almost 1.5&nbsp;°C (2.7&nbsp;°F) in the last 50 years, resulting in a shorter period where the lake is covered by ice.<ref name=ScienceDaily2017/> At some locations, [[hydrothermal vent]]s with water that is about {{convert|50|C|F|abbr=on}} have been found. These are mostly in deep water but locally have also been found in relatively shallow water. They have little effect on the lake's temperature because of its huge volume.<ref name=Gurulev/>

Stormy weather on the lake is common, especially during the summer and autumn, and can result in waves as high as {{convert|4.5|m|ft|abbr=on}}.<ref name=FEOW/>

<gallery mode="packed" heights=150>
File:Baikal-S1999276045323.png|Lake Baikal as seen from the [[OrbView-2]] satellite
File:Ice Melting on Lake Baikal - NASA Earth Observatory.jpg|Spring ice melt underway on Lake Baikal, on 4 May{{efn|Note the ice-covered north, while much of the south is already ice-free.}}
File:Baikal lake Crack in the ice.jpg|Ice cover survey on the lake
File:Circles in Thin Ice, Lake Baikal, Russia.jpg|Circle of thin ice, diameter of {{convert|4.4|km|1|abbr=on}} at the lake's southern tip, probably caused by [[convection]]
File:Selenga delta.jpg|Delta of the [[Selenga River]], Baikal's main tributary
</gallery>