Rock-ice avalanche led to Chamoli floods: Study

After months of debate over what led to the Uttarakhand floods in February 2021 — glacial lake outburst or rockslide — a team of 53 international scientists has confirmed “an extraordinary rock and ice avalanche and debris flow” was the cause, using a computer model to reconstruct “in almost real time” how the flood unfolded. But only a part of the rock-ice mass collapsed from Ronti Peak in February, they warned, leaving a substantial chunk vulnerable.
The findings, by scientists from universities of Colorado, Washington, Zurich, Potsdam, Utah, Toulouse, Heidelberg, Geneva, Newcastle, Oslo and Utrecht, among several others, were published in the ‘Science’ journal on Thursday.
“There is no ambiguity that the event was a rock-ice avalanche,” co-author Irfan Rashid told TOI. It could happen again. “High-resolution Google Earth data over the Ronti Peak suggests that only a bigger hanging glacier collapsed in February,” he said.
Lead author Dan Shugar said, “ At Nanda Devi and Nanda Ghunti glaciers (where it was suggested the glacial lake originated), no evidence was observed of any changes in days prior to (the flood).”
Seismic data from two stations indicated that around 10.21am, a 20 million m3-mass of rock (80%) and ice (20%) broke off from an altitude of 5,500m above sea level. “The frictional heat generated nearly melted off the ice during descent,” Shugar said.