The deadliest earthquake in South American history, the Ancash earthquake in Peru, occurred in 1970. On 31 May, a magnitude 7.9 earthquake struck off Peru’s north-central coast, shaking the Ancash and La Libertad regions for roughly 45 seconds.
The greatest devastation came when the shaking destabilized the north side of Mount Huascarán. A huge avalanche of rock, ice, snow, mud, and water raced down the mountain and buried Yungay and nearby communities. The slide traveled roughly 18 kilometres at an estimated average speed of 280–335 kilometres per hour. Total deaths from the earthquake and resulting landslide are generally estimated at about 66,800 to 70,000.
Huaraz was also heavily damaged, while infrastructure across a wide area was destroyed, complicating rescue and relief efforts. The disaster became known as the Great Peruvian earthquake and remains Peru’s most catastrophic natural disaster. The year 1960 is a tempting alternative because of Chile’s great earthquake, but that event was not deadlier. The 1985 and 2007 choices refer to other major earthquakes, not the Ancash disaster.