Usoi Dam

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The Usoi Dam is a natural landslide dam along the Murghab River in the Central Asian nation of Tajikistan.

The dam was created on February 18, 1911, when a great earthquake estimated between 8 and 9 on the Richter Scale caused a massive landslide to block the flow of the river. The Usoi is formed of approximately two cubic kilometers 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, and rises to a height of 500 m to 700 m from the original valley floor.^[1] The basin formed by Usoi now holds Sarez Lake, a 55.8-kilometer long lake holding 16,074 cubic kilometers of water.

Geologists are concerned that 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.^[2] Collapse of the dam would unleash a locally catastrophic flood, as the Murghab's river valley tends to be relatively narrow and steep, which would focus and maintain a flood's destructive power.