On 31 May 1970, an earthquake off the coast of Peru caused a substantial section of the north slope of Mt. Huascaran to collapse. [Situated in the Cordillera Blanca, the world’s highest tropical mountain range, Mount Huascarán rises to 6768 m above sea-level.] The avalanche moved down hill at a speed of 100 MPH with a mass of roughly 80 million cubic feet of ice, mud and rock. It ran nearly 11 miles, burying the towns of Yungay and Ranrahirca in up to 300 feet of rock and debris. Estimates suggest that the earthquake killed over 20,000 people.

* The avalanche started as a sliding mass of glacial ice and rock about 3,000 feet wide and one mile long. The avalanche swept about 11 miles to the village of Yungay at an average speed of more that 100 miles an hour. The fast-moving mass picked up glacial deposits and by the time it reached Yungay, it is estimated to have consisted of about 80 million cubic yards of water, mud, and rocks. Photo courtesy of Servicio Aerofotografico Nacional de Peru, 13 June 1970. – landslide.usgs.gov