Cryospheric Hazards in the Rio Volcan 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 Rio
Volcan 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 three moraine-dammed glacial lakes with a
cumulated area of up to 24 hectares in front of the El Morado glacier
and two innominates. The lakes are still enlarging along with the
glacier shrinkage, conforming three potential glofs in the region.
Several debris-free glaciers have a very steep front, steeper than 30
degrees, 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 Jose; volcano. The latter would have happened in
the late 1940s according to literature. In addition, at least four
glaciers showed abnormal advance rates in the early 1990s of up to 100
m/yr, along with the surge-like behavior of the Loma Larga glacier.
Providing further knowledge of this complex region is key in order to
enhance understanding and hazard management on a day to day basis.