The Usoi Dam is a natural landslide dam along the Murghab River in Tajikistan . At 567 metres (1,860 ft) high, it is the tallest dam in the world, either natural or man-made. The dam was created on 18 February 1911, when the 7.4- M s Sarez earthquake caused a massive landslide that blocked the flow of the river.
3-527: The dam is formed of approximately 2 cubic kilometres (0.48 cu mi) of rock dislodged from the steeply sloped river valley of the Murghab , which cuts from east to west through the high and rough Pamir Mountains . It is named after the village of Usoi, which was completely buried by the 1911 landslide. The dam rises to a height of 500 to 700 metres (1,600 to 2,300 ft) from the original valley floor. The basin formed by Usoi Dam now holds Sarez Lake ,
6-594: A 55.8-kilometre (34.7 mi)-long lake holding 16.074 cubic kilometres (13,031,000 acre⋅ft ) of water. Water does not flow over the top of the dam, which would quickly cause it to erode away; instead, water seeps out of the base of the dam at a rate which approximately matches the rate of inflow, maintaining the lake at a relatively constant level. The level thus only rises an average of 20 cm per year. The flow averages about 45 cubic meters per second, with an annual variation of 35-80 cubic meters per second and dissipates about 250 megawatts. Geologists are concerned that
9-495: The Usoi Dam may become unstable during future large-magnitude earthquakes, which are relatively common in the seismically active Pamirs, and might collapse due to liquefaction or subsequent landslides during such an event. Collapse of the dam would unleash a locally catastrophic flood. The Murghab's river valley tends to be relatively narrow and steep. This would focus and maintain any flood's destructive power as it swept through
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