TANGANYIKA, a vast lake in East-Central Africa, the longest freshwater lake in the world, measuring about 450 m. with a general breadth varying from 3o to 45 m., and an area of about 12,700 sq.m. It lies at an altitude of about 2,536 ft., is 4,708 ft. deep, therefore its floor is 2,172 ft. below sea-level. After Lake Baikal this is the deepest freshwater lake in the world. It occu pies the southern end of the great western rift-valley which termi nates suddenly at its southern point, but the line of depression is continued south-eastward through Lakes Rukwa and Nyasa, from which Tanganyika is separated by the Ufipa plateau. Another branch of the rift-valley passes south-westward into the Eastern Congo, branching from the northern end of the lake. North of Tanganyika the valley is suddenly interrupted by a line of young eruptive ridges, which dam back the waters of Lake Kivu (q.v.) but have recently been cut through (in about the year 1906) by the outlet of that lake, the Russisi which enters Tanganyika by several mouths at its northern end. The flat plain traversed by the lower Russisi was evidently once a portion of the lake floor. Tan ganyika has been formed by the subsidence of a long narrow tract of country relatively to the surrounding plateaux which fall to the lake in abrupt cliffs, some thousands of feet high in places. The geological formations thus exposed show that the plateaux are composed of a base of Archaean gneisses and schists, overlain by enormous deposits of unfossiliferous red sandstones, con glomerates and quartzites (the Tanganyika Sandstones), which reach 3,00o ft. in thickness at the south end of the lake. They are almost certainly Archaean in age. The formation of the rif t valley dates from late Tertiary times. Besides the plain to the north a considerable area near the Lukuga outlet was once cov ered by Tanganyika. Although drinkable, the water of the lake seems at times at least to be very slightly brackish, and it was supposed by some that no outlet existed until in 1874, Lieutenant Cameron showed that the surplus water was discharged periodi cally towards the Upper Congo by the Lukaga river, about the middle of the west coast. Observations during the last 5o years indicate that the level of the lake frequently changes but these alterations are probably due only to fluctuations in rainfall.
The lake is fed by a number of rivers and small streams, but is by no means the centre of a large drainage area. The Mala garasi is the largest feeder. The lake is subject to occasional storms which leave a heavy swell and impede navigation.
Vegetation is generally luxuriant, and forest clothes portions of the mountain slopes. The lake lies on the dividing line between the floral regions of East and West Africa, and the oil-palm char acteristic of the latter is found on its shores. The largest timber
tree is the mvule, which attains vast dimensions. The more level parts of the shores have a fertile soil and produce a variety of crops, including rice, maize, manioc, sweet potatoes and sugar cane. The waters display an abundance of animal life, croco diles and hippopotami occurring in the bays and river mouths, which are also the haunts of water-fowl of many kinds. Fish are also plentiful. Various sections of the Bantu division of the negro race dwell around the lake, those on the west and south west showing the most pronounced negro type, while the tribes on the east exhibit some intermixture with representatives of the Hamitic stock, and (towards the south) some trace of Zulu in fluence. The surrounding region has been overrun by Arabs and Swahili from the East African coast.
The lake was first visited in 1858 by Burton and Speke who reached Ujiji, which was the spot where in 1871 Dr. Livingstone was found by Stanley. The southern half of the lake was first circumnavigated by Lieutenant V. L. Cameron in 1874, and the whole lake by Stanley in 1876.
In the partition of Africa among the European powers the shores of Tanganyika were shared by Belgium, Great Britain and Germany, Great Britain holding the southern extremity, Ger many the east and Belgium the west. After the World War the German portion became part of the British mandated territory of Tanganyika whilst Belgium extended her boundaries to include the mountains of Urundi on the north-east of the lake shore.
The chief towns on the lake are Sumbu, Niamkolo, Kasango, Ujiji and Kigoma (all British), Usumbura, Uvira, Albertville, Vua, Baudouinville and Moliro (all Belgian). Steamers ply on the lake traversing its length in about four days, the best harbours being at Kasanga, Kigoma, Usumbura and Albertville. The East African Central railway from Dar-es-Salaam terminates at Ki goma, whilst a railway passes down the Lukuga valley from Albertville.
earlier works see the narratives of Burton, Livingstone, Cameron, Stanley, Ramsey, Wallace, E. C. Hore, H. Glauning, E. Kohlschiitter ; M. Fergusson, in Geol. Mag. August i90! ; E. Stromer, in Petermanns Mitteil., December 1901 ; R. Codrington, in Geogr. Journal, May 1902, W. H. Hudleston, in Transactions Victoria Inst., 1904; F. S. Joelson, The Tanganyika Territory (1920) ; J. C. Smuts, German East Africa (Geogr. Journal, 1918) ; also papers of the results of Dr. W. A. Cunnington's expedition in Proceedings of the Zoological Society 1906, etc.; Journal of the Linnean Society, 1907, and official reports of the Tanganyika Territory (Annual).