BAIKAL, a lake of East Siberia (known to the Mongols as Dalai-nor, and to the Turkish tribes as
the sixth in size in the world and the largest fresh-water basin of Eurasia. It stretches from south-west to north-east (52° and 56° N. and
to
E.), lying in the Buriat-Mongol A.S.S.R., except for the coastal area north and south of the outlet of the Angara river, which is in the Irkutsk province (q.v.) and has a length of 674km. and a width of from 25 to 74 kilometres. Its south end penetrates into the high plateau of Asia, and the lake lies entirely in the moun tain zone north-west of that plateau. Its area is 33,000sq.km., i.e., nearly as great as Switzerland. The length of its coast-line is 2,200 kilometres. Its altitude is 462 metres above sea level and 4o metres above the level of the Angara at Irkutsk (Zapiski, Russ. Geog. Soc., xv., 1885). Its level changes regularly during the year, being lowest in April and highest in September. The ampli tude of variation is about 8o centimetres. Its level is also subject to irregular oscillations, and after five weeks of heavy rain in 1869 it rose more than two metres and submerged a large area at the mouth of the Selenga. The drainage area is estimated at 650,000 sq.km., and the intake of fresh water at 162cu.km. per annum.
Drizhenko, working in 1897-1902, produced a map published in Pilot for the Lake Baikal. This shows that, as regards depth, the lake may be divided into three sections. The southern section stretches from the west end to the Selenga delta and is enclosed between spurs of the East Sayan mountains in the west and the Khamar-daban mountains in the east. Both these ranges have precipitous granitic slopes down to the lake and into its depths, with soundings in places of more than 1,400 metres. From the Selenga delta, with its large alluvial deposits, a rise of the lake floor stretches north-west and is covered by only 200 to 53o metres of water. The second section stretches from the mouth of the Selenga to Svyatoi Nos on the east coast, and is extremely deep, a sounding of 1,522 metres being taken quite close to Cape Ishimei on the island of Olkhon; the lake floor here lies 1,060 metres below sea-level, and is thus the deepest crypto-depression of the earth's surface. As the average depth of Baikal is 700 metres, it is the deepest lake in the world, and in proportion to its area it has the largest volume of water, estimated at 23,00o cu.km., or approximately the volume of the Baltic and the Katte gat, though the surfaces of these together have an area 12 times that of Baikal. The third section stretches from Svyatol Nos to the north end ; here the depths gradually diminish, but soundings of more than Soo metres occur almost everywhere. The water is beautifully clear.
The surface-layers have summer tempera tures of 55-1° to 57°, both close to the shores and at some distance from the mouth of the Selenga, but these warmer layers are not deep, and a nearly uniform temperature of 39° is found from a depth of 200 metres right down to the bottom. At various places round the shores, e.g., the mouth of the Barguzin, hot springs ex ist. The lake freezes usually at the end of December, or in the beginning of January, and it remains frozen till the second half of May. Evaporation exercises a certain influence on the climate of the surrounding country, while absorption of heat for thawing of ice has a notable cooling effect in early summer. In summer the climate is cooler, in winter warmer than that of the surrounding region, the range of air temperature on the lake being only 56° as against 79° away from the lake.
Lake Baikal receives over 30o streams, mostly short mountain torrents, besides the Upper Angara, which enters its north-east extremity, the Barguzin, on the east, and the Selenga on the south-east. Its only outflow is the lower Angara, which issues through a rocky cleft on the west shore. The Irkut no longer reaches Baikal, though it once did so. After approaching its south-west extremity it abandons the broad valley which leads to the lake, and makes its way northwards through a narrow gap in the mountains and joins the Angara at Irkutsk.
Save at the Selenga delta, Lake Baikal is sur rounded by mountains. The Khanar-daban border-ridge (the summit of a mountain of the same name is 1,8o0 metres above the lake), falling, with steep cliffs, towards the lake. fringes it on the south; a massive, deeply-ravined highland occupies the space between the Irkut and the Angara; the Onot and Baikal ridges (also Primorskiy) run along its north-west shore, striking it diagonally; a complex of still unexplored mountains rises on its north-east shore; the Barguzin range impinges upon it obliquely in the east ; and the Ulanburgasi mountains intrude into the delta of the Selenga.
Baikal may already have existed in the Jurassic period. It has certainly existed since the Miocene. At times it has stretched westwards into what is now the valley of the Irkut, and northward and eastward up the lower valleys of the Upper Angara and the Barguzin, but it has never been in connection with the Arctic ocean. It is a very old relict-lake, a deep depres sion among great mountain lines, which is still progressing, and earthquakes are frequent along its shores.
Dybowski and Godlewski (1876) and Korotnev (190 2) found the fauna much richer than was supposed, and highly peculiar. A few animals of marine affinities are found ; e.g., a seal (Phoca foetida sibirica, Gmelin) but these animals have wandered up the lower Angara and have thus reached the lake. There may also have been at various times seasonal expanses of water from melting ice in the Yenisei basin. On the whole the fauna, and especially the lower animals in it, are, as it were, a sort of fresh-water museum of ancient species, several of which are endemic and peculiar. Baikal has 188 species of Gammarus, more than half the species of this genus described for the world; of these 184 are found only here. The waters swarm with fish (sturgeons and salmonidae), and herring (Salmo omul) is the chief product of the fisheries, though notably fewer have been taken within the last so years. The most interesting fish is Comephorus baikalensis, resembling fishes living at great depths of the ocean. Plankton is very abundant. The little Lake Frolikha, situated close to the northern extremity of Lake Baikal, and communi cating with it by means of a river of the same name, contains a peculiar species of trout, Salmo erythreas, which is not known elsewhere.
The lake was discovered in 1643, since when boats have been in use on it ; steamers having been introduced in 1844. Sudden storms and absence of good bays and ports, hinder navigation. The principal port on the western shore, Listvinichnoe, near the outflow of the Angara, is an open roadstead at the foot of steep mountains. Steamers ply from it to Misovaya (Posolskoe) on the opposite shore, a few times a year, to Verkhne Angarsk, at the northern extremity of the lake, and frequently to the mouth of the Selenga, which they ascend to Bilyutai, near the Mongolian frontier. They bring back tea, imported by way of Kiakhta, while grain, cedar nuts, salt, soda, wool and timber are shipped on rafts down the Khilok, Chikoi and Uda (tributaries of the Selenga), and manufactured goods are taken up the river for export to China, but now (1928) there is only little traffic. At tempts are being made to render the Angara navigable below Irkutsk down to the Yenisei. In winter, when the lake is covered with ice 1 metre thick, it is crossed on sledges from Listvinichnoe to Misovaya. But a highway, available all the year round, was made in 1863-64 around its southern shore, partly by blasting the cliffs, and it is (since 1905) followed by the trans-Siberian railway.
"Hydrographic Reconnoitring of Lake Bibliography.-Drizhenko, "Hydrographic Reconnoitring of Lake Baikal," in Izvestia, Russ. Geogr. Soc. (1897 and 1902) ; Drizhenko, Pilot for the Baikal Sea (1908) and Atlas of the Baikal Sea (1908) ; Chersky, "Geological Map of Shores of Lake Baikal," 63m. to the inch, in Zapiski, of Russ. Geogr. Soc., xv. (1886) ; "Report of Geological Exploration of Shores of Lake Baikal," in Zapiski, of East Siberian Branch of Russ. Geogr. Soc., xii. (1886) ; Obruchev, "Geology of Baikal Mountains," Izvestia of same society (xxi. 4 and 5, 189o) ; Dybowski and Godlewski on "Fauna," in same periodical (1876) ; Witkowski, on "Seals" ; Yakovlev, "Fishes of Angara," in same periodical (189o-93) ; "Fishing in Lake Baikal and its Tribu taries," in same periodical (1886-9o) ; and La Geographie (No. 3, 5904). A detailed summary of knowledge concerning Baikal has recently been given, with many bibliographical references by H. Johansen (Mitteil, Geogr. Gesell., Munchen, bd. xviii., 1925).
