Hazardous processes and events from glacier and permafrost areas: Lessons from the Chilean and Argentinean Andes

Glacier and permafrost hazards such as glacial-lake outburst floods and rock-ice avalanches cause significant socio-economic damages worldwide, and these processes may increase in frequency and magnitude if the atmospheric temperature rises. In the extratropical Andes nearly 200 human deaths were linked to these processes during the twentieth century. We analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio-economic damages in this region in historic time (including glacial lake outburst floods, ice and rock-ice avalanches and lahars) to unravel their causes and geomorphological impacts. In the extratropical Andes, at least 15 ice-dammed lakes and 16 moraine-dammed lakes have failed since the eighteenth century, causing dozens of floods. Some floods rank amongst the largest events ever recorded (5000×10⁶m³ and 229×10⁶m³, respectively). Outburst flood frequency has increased in the last three decades, partially as a consequence of long-term (decades to centuries) climatic changes, glaciers shrinkage, and lake growth. Short-term (days to weeks) meteorological conditions (i.e. intense and/or prolonged rainfall and high temperature that increased meltwater production) have also triggered outburst floods and mass movements. Enormous mass failures of glaciers and permafrost (> 10×10⁶m³) have impacted lakes, glaciers, and snow-covered valleys, initiating chain reactions that have ultimately resulted in lake tsunamis and far-reaching (> 50km) flows. The eruption of ice-covered volcanoes has also caused dozens of damaging lahars with volumes up to 45×10⁶m³. Despite the importance of these events, basic information about their occurrence (e.g. date, causes, and geomorphological impact), which is well established in other mountain ranges, is absent in the extratropical Andes. A better knowledge of the processes involved can help to forecast and mitigate these events.