Keystone-SDA
A research team from the EPFZ studied torrential lavas in Valais with unequaled precision. Thanks to high -resolution measures, the study was able to highlight unexplained factors that determine their destructive force.
(Keystone-ATS) The international team led by the Federal Polytechnic School of Zurich (EPFZ) attended live the trigger of a torrential lava in June 2022 in the Illgraben, above the Valais commune of Loèche.
No month of 25,000 cubic meters of materials – a flow of water, earth and scree – then poured out four kilometers in the Illbach bed, before throwing itself into the Rhône, the EPFZ said on Wednesday in a press release.
Scientists followed the natural phenomenon using several measurement stations and high -precision 3D laser scanners, called Lidars. At the top of the valley, a two -meter -high forehead rapidly advancing was observed at the tip of the mud flow, containing blocks of a size up to a cubic meter.
Lower in the valley, the mud flow was lower, but powerful and fast waves occurred regularly on the surface. Seventy waves of this type were counted by scientists during the half hour lasted by the mudslide.
Central role of thrusts
These thrusts play a central role in the destructive force of torrential lavas because they make the flow of mud particularly powerful and fast. According to the authors, the physical processes behind these thrusts were so far little known.
“We have been able to demonstrate that pushes occur spontaneously on the surface of the flow. They come from small irregularities that increase over time, becoming larger and faster, until they reach their maximum destructive force, “said Jordan Aaron, professor at EPFZ, quoted in the press release.
Based on this study, it would be possible to estimate in the future if thrusts are to be expected during a torrential lava and what is their destructive force. This analysis would make it possible in the medium term to improve danger management, according to Professor Aaron.
Scientists have also been able to deduce measurement data that large blocks of rock strongly influence the local dynamics of currents in torrential lavas. This phenomenon is not taken into account in most current forecasts.
Scientists from the Federal Institute for Forest Research, Snow and Landscape (WSL) and the British Manchester University also participated in this research, published in the journal Communications Earth & Environment.