fragile housing stock, typical of structures elsewhere in the Río Santa valley, was highly vulnerable to seismic activity. Other prominent features of Yungay included the central Plaza de Armas surrounded by palm trees, which hosted events including the fiesta of Santo Domingo, and the elevated cemetery, which was actually built on top of a pre-Inca burial mound which may be as old as 10,000 years. In the years leading up to 1970, Yungay – sometimes nicknamed "Pearl of the Huaylas Corridor" – had become one of the most popular tourist destinations in Peru due to its picturesque location, architecture, and proximity to Huascarán and the Llanganuco lakes. Yungay had been struck by disaster before; it was reported to be "almost completely wiped out by an avalanche" in 1872, implying an avalanche at least equal to the magnitude of the 1970 event. 1962 Ranrahirca avalanche On January10, 1962, part of Glacier 511 collapsed, causing 10millionm3 (13millionyd3) of rock, ice and snow to crash down into Río Llanganuco. The slide destroyed nine villages and killed more than 4,000 people. The entire town of Ranrahirca, which was built on the Llanguanuco fan at the edge of the slide path, was flattened; some 2,900 people died in Ranrahirca alone. Residents had little to no warning, as less than four minutes passed from the beginning of the slide before the flow reached the Río Santa. Everything in the wave's path was destroyed, and corpses were washed as far as the Pacific Ocean, downstream. This slide was not caused by an earthquake, nor were seven other large avalanches and debris flows that occurred in the Santa Valley between 1940 and 1970. Rather, the glacier had fractured under its own weight. Due to the steep slope of the underlying rock and lubrication by glacial melt, there was nothing to stop the ice from sliding downhill at high speed. In the wake of this and other glacier-related disasters in the Ashish region, notably glacial lake outburst floods that destroyed parts of Huaraz in the preceding two decades, the national government had tried to push forward "hazard zoning" which would limit development in flood and avalanche zones. However, these efforts were largely unsuccessful due to resistance by locals, who feared the economic and cultural disruption that would result from forced relocation. Post-1962 observations and controversy In September 1962, the Massachusetts Institute of Technology sponsored a glaciological expedition to assess