Cryospheric Hazards in the Río Volcán Basin, Chilean Central Andes: One Region, Multiple Phenomena

Abstract:

The Chilean central Andes are known for its variety of cryospheric landforms, which have included almost every kind of glacier since their first exploration back in the XIX century. However, there has been a severe reduction of the glacierized area since the 1950s, driven by climate change and enhanced due to the megadrought, which has endured for over a decade in the region. Such decline in glacier volume combined with temperature increasing and precipitation reduction can lead to different types of instabilities. In mountainous regions of high public affluence, glacial instabilities are considered as potential hazards leading to the loss of lives and infrastructure.

Here we analyze the Río Volcán basin (-32.82°/-70.00°), located 40 km east of Santiago city in the international border with Argentina. The region is known for its closeness to the capital, which favors outdoor activities and hydroelectric power development. Elevation ranges from 3380 to over 6000 m a.s.l. at the San José Volcanic Complex, allowing conditions for coexistence of mountain glaciers, valley glaciers, rock glaciers and glaciarets. According to the public Chilean Glacier Inventory, there are more than 140 mapped cryoforms occupying an area of 57 km².

Beside snow avalanches, there are multiple factor that provide ideal conditions for cryospheric hazards involving glaciers. Some of those factors are pointed out on the following:

The presence of an active volcanic complex sets up the triggering agent for lahars and mixed snow/ice avalanche occurrence. There are two moraine-dammed glacial lakes with a cumulated area of up to 21 hectares in front of the El Morado glacier and one innominate. Both lakes are still enlarging along with the glacier shrinkage, conforming two potential glofs in the region. Several debris-free glaciers have a very steep front, steeper than 60°, favoring the occurrence of ice falls and ice avalanches. There is a reported surge event in the Nieves Negras glacier, located at the south face of the San José volcano. The latter would have happened in the late 1940s according to literature. In addition, two glaciers showed surge-like behavior in the early 1990s, with abnormal advance rates of up to 100 m/yr.

Providing further knowledge of this complex region is key in order to enhance understanding and hazard management on a day to day basis.