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springs that periodically eject hot water and steam. Geysers are found in regions of present or recent volcanic activity, where there is an intensive flow of heat from a volcanic focus. They may take the form of small, truncated cones with rather steep slopes, or they may be low, very gently sloping domes, small, bowl-shaped depressions, basins, or irregularly shaped pits. On the bottom or walls are orifices in the form of tubular or slitlike channels.
Typical geyser activity involves repeated periods of quiescence, when the basin is filling with water, periods of eruption of a mixture of steam and water, and intensive ejections of steam, gradually giving way to quiet discharge and cessation, followed by another period of quiescence. Geysers are classified as regular or irregular. In the former, the duration of the cycle and its individual stages is almost constant; in the latter, it varies. In some geysers, the length of individual stages is measured in minutes and dozens of minutes, and the quiescent state lasts from several minutes to several hours or days. The water ejected by geysers is relatively pure or slightly mineralized (1 or 2 g per liter), containing sodium chloride or sodium chloride hydrocarbonate, with a relatively large amount of silica, from which rock known as geyserite —similar to opal—forms at orifices and on the slopes of geysers. Most geyser water is of atmospheric origin, with perhaps an admixture of water from the magma. Geyser activity is generally of relatively short duration and depends on a number of conditions, such as diminution of heat flow and cessation of the movement of subterranean water in geyser channels.
Geysers occur on Kamchatka in the USSR and in Iceland, North America, New Zealand, Japan, and China. Large geysers were discovered near Kikhpinych Volcano in the Geizer Valley on Kamchatka in 1941. There is a total of about 100 geysers on Kamchatka. About 20 of them are large— equal in terms of size and eruptive force to the active geysers of Iceland, Yellowstone National Park in the USA, and New Zealand. Velikan—the largest geyser on Kamchatka —hurls streams of water 40 m into the air and steam to heights of several hundred meters. Iceland has about 30 active geysers, among which the Leaping Witch (Gryla) is outstanding. It hurls a mixture of steam and water to a height of 15 m approximately every two hours. Among the geysers of Yellowstone National Park (about 200), the largest are Giant and Old Faithful. The former hurls steam and water as high as 40 m at three-day intervals, and the latter erupts to a height of 42 m every 53-70 minutes: Te Tarata, the mighty and most beautiful geyser of New Zealand, was situated on a terraced hill of pink siliceous tuff. It disappeared during the eruption of Tarawera Volcano in 1886. Another geyser in New Zealand, Waimangu—the largest and most powerful in the world—erupted irregularly at intervals of five to 30 hours from 1899 through 1904. At every eruption Waimangu ejected about 800 tons of water, and rocks caught in the stream of water were lifted to a height of 457 m. The geyser became dormant when the water level in nearby Lake Tarawera dropped 11m. Outstanding among present-day New Zealand geysers is Pohutu, which erupts periodically to a height of 20 m.
There are a number of hypotheses about the formation and periodic activity of geysers. According to detailed data gathered by V. V. Aver’ev, A. S. Nekhoroshev, and V. M. Sugrobov, geysers cannot exist without being fed in parts of their channels near the surface by super-heated water with temperatures of more than 100° C. When the water moves up along a channel, its pressure diminishes and the water boils, causing the resiliency of the steam to increase rapidly. The steam then overcomes the pressure of the water in the channel and ejects the water. When the eruption begins, all the water in the channel boils and is ejected because of a considerable increase in the volume of the mixture of water and steam. Somewhat cooled, some of the ejected water falls into the basin of the geyser and its channel, and a large amount of the water is absorbed into the channel from the surrounding rock, heated (overheated in lower parts of the channel), and again steam is formed and a mixture of water and steam is ejected. The escaping water vapor and hot water of geysers can be used to heat buildings and hothouses and to supply power-generating facilities.
REFERENCESNaboko, S. I. “Geizery Kamchatki.” Trudy Laboratorii vulkanologii, 1954, vol. 8.
Nekhoroshev, A. S. “K voprosu o teorii deistviia geizerov.” Dokl AN SSSR, 1959, vol. 127, no. 5.
Sugrobov, V. M., and V. V. Aver’ev. “Obvodnennost’ porod Pauzhetskogo mestorozhdeniia i usloviia tsirkuliatsii vysokotermal’-nykh vod.” In the collection Pauzhetskie goriachie vody na Kamchatke. Moscow, 1965.
Allen, E. T., and A. L. Day. Hot Springs of the Yellowstone National Park, Carnegie Institution of Washington, publication no. 466. Washington, D. C., 1935.
Barth, T. F. W. Volcanic Geology, Hot Springs and Geysers of Iceland, Carnegie Institution of Washington, publication no. 587. Washington, D. C., 1950.
V. I. VLODAVETS