Revista Chilena de Historia Natural 82 (2): 245-264, 2009
RESEARCH ARTICLE
Dendrochronological reconstruction of spatial and temporal patterns of snow avalanches in
the Patagonian Andes
Snow avalanches are a major natural hazard in a large number of mountainous regions
around the world. Every year, infrastructure is destroyed and human lives lost as a consequence of catastrophic avalanche events.
Numerous roads and settlements in the Andes are located adjacent to avalanche tracks, for which little is known about maximum
extents, return periods or impact pressures. Utilizing dendrochronological techniques we were able to reconstruct the occurrence
dates and affected areas of past snow avalanche events. Individual Nothofagus pumilio trees with visible damage of past
avalanche disturbances were sampled in the tracks, borders and run-out zones of 11 avalanche tracks located at Loma de las
Pizarras, near El Chaltén, Santa Cruz, Argentina. In addition, control sites were sampled to determine the growth patterns of
undisturbed trees. Our analyses indicate that scars, eccentricity variations in the wood, abrupt growth changes and reaction wood are
the main indicators associated with avalanche disturbances in N. pumilio. Based upon a quantitative weighting of the
different indicators and on the sampling depth, we calculated an index of avalanche occurrences for each avalanche track. Considering
the avalanche activity at the 11 studied tracks, the years with the largest number of events were 1936, 1966, 1978 and 1995. In
addition, climatic records were analyzed to explore the relationships between avalanche events and monthly precipitation and
temperature variations. The years with the largest number of avalanche events are significantly correlated with abundant precipitation;
relationships with temperature variations were not recorded. The results of this study confirm the dendrochronological potential of
N. pumilio for reconstructing spatial and temporal patterns of snow avalanche events in the Patagonian
Andes.
Key words:
snow avalanches,
dendrochronology, Nothofagus pumilio, Patagonian Andes
