moraine, water and uprooted trees. With area soils saturated near the end of the rainy season, and the large amount of snow and ice scraped off the glacier surface, the avalanche quickly liquefied into a fluid, fast-moving mudflow. The maximum volume of mudflow was as much as 50-100 millionm3 (130millionyd3), and it reached speeds of up to . Some debris projectiles launched ahead of the main flow may have exceeded . According to a U.S. Geological Survey report published the same year, the mudflow may have achieved its unusually high speed due to "air-cushioned flow", a mixture of snow, ice and entrapped air that allowed the bulk of the material to essentially float over the ground. The initial acceleration of the mass down the low-friction glacial surface was also a major factor, catapulting the material downhill at a much higher speed than if it had slid over bare rock or earth. Destruction of Yungay In Yungay, people rushed outside after the earthquake hit; many flocked to churches to shelter and pray. Most buildings in the city were damaged or destroyed by the earthquake, though initial casualties were low compared to the mudflow that followed. The mudflow struck Yungay, from the avalanche origin, an estimated 1 minute, 42seconds after the earthquake began. Although the nearly hill of Cerro de Aira stood between Yungay and the Llanganuco valley, the mudflow struck the ridge at a high enough speed – some – that part of it leapt over the crest, first destroying the villages of Shillkop, Aira and Ongo before descending upon Yungay. A large air blast preceded the debris flow, followed by a rain of boulders and large debris before the main, semi-liquid wave struck. The wind blast was "strong enough to throw people to the ground and in some places to topple trees." Giant rocks "bounced and rolled" towards Yungay, leaving huge craters in the ground and flattening buildings that had not been already destroyed by the earthquake. The mudflow itself was described by survivors as "rolling", "wavelike" or "a rolling confused motion." Due to the speed of the flow, there was no time to evacuate. Practically every man-made structure in Yungay except a few on the outskirts were destroyed, and thousands of people were killed instantly. Survivor Mateo Casaverde described the scene: Effects elsewhere The majority of the mudflow headed straight down Río Llanganuco, which formed the most direct path