A gargantuan landslide in China generated enough heat to vaporize some of the sliding material, creating superheated steam that helped the avalanche of rock to barrel downhill.
In 2008, the magnitude-8.2 Wenchuan earthquake shook loose more than a cubic kilometre of soil and stone from the summit and flank of Daguangbao mountain in central China. A team led by Runqiu Huang at Chengdu University of Technology in China analysed rock samples from the landslide to study conditions within the flow. By comparing rock samples with the results of friction experiments in the laboratory, the scientists concluded that temperatures at the boundary between the slide and the intact slope reached at least 850°C.
That would have partially vaporized a mineral called dolomite in the rock, releasing high-pressure, high-temperature carbon dioxide and steam that would have allowed the landslide to flow. At the same time, the immense pressure on the minerals would have caused them to recrystallize, lubricating the sliding surface and helping the debris to hurtle more than 4 kilometres from its original location.
The work offers clues to how big landslides travel long distances.