Memorial of the Czechoslovak expedition of Mai 1970

On 31 May 1970, the Ancash earthquake caused a substantial part of the north side of the mountain to collapse. The avalanche mass, an estimated 80 million cubic feet of ice, mud and rock was about half a mile wide and a mile long. It advanced about 11 miles (18 km) at an average speed of 280 to 335 km per hour.[11] burying the towns of Yungay and Ranrahirca under ice and rock, killing more than 20,000 people.[12] At least 20,000 people were also killed in Huaraz, site of a 1941 avalanche which killed over 6000 (see Palcacocha Lake).[13] Estimates suggest that the earthquake killed over 66,000 people.[14][15]
Also buried by an avalanche was a Czechoslovak mountaineering team, none of whose members was ever seen again.[16] This and other earthquake-induced avalanche events are often described incorrectly as "eruptions" of Huascarán, which is not of volcanic origin.
Source: en.wikipedia.org/wiki/Huascar%C3%A1n
Photo by Roman Barta and Larsik from: mw2.google.com/mw-panoramio/photos/medium/19747028.jpg on www.panoramio.com