One of the world’s largest recorded landslides occurred on April 9, 2000, when more than 100 million cubic meters (3.5 billion cubic feet) of loose rock, ice, and other debris tumbled down a steep, narrow gorge in eastern Tibet.
Within ten minutes, the slurry of debris—which included granite and marble boulders, snow, and sediment—moved nearly 10 kilometers (6 miles) and dropped from an elevation of 5,520 meters (18,110 feet) to the valley floor 2,190 meters above sea level. The debris, lubricated by recent rainfall and meltwater from glaciers on the surrounding mountain peaks, slid through a gully carved by Zhamu Creek at velocities up to 14 meters per second (31 miles per hour).
By the time the mass of material stopped, it had buried the Yigong River, creating a debris dam that blocked the flow of the river. The dam occupied 2.5 square kilometers (1 square mile) and was 90 meters (295 feet) high at its tallest edge. River water began to back up immediately, creating a large lake behind the dam. As time passed, increasing volumes of water began to seep through the bottom of the dam, muddying the river water downstream. Meanwhile, the area and volume of the lake continued to grow.
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Earth Observatory, June 2012