Rockslides and rock avalanches in the Central Andes of Argentina and their possible association with permafrost degradation

CARLA TAPIA BALDIS; DARIO TROMBOTTO LIAUDAT

PERMAFROST AND PERIGLACIAL PROCESSES

JOHN WILEY & SONS LTD

Lugar: Londres; Año: 2019 p. 1 - 18

1045-6740

The identification of hazardous slopes with degrading permafrost is a key task in the mountain periglacial environment. If some rockslides were preconditioned by rock wall permafrost since the past, similar events may be triggered from present unstable rock walls. An inventory of rockslides and rock avalanches in the austral part of the Santa Cruz river basin (31°40? to 31°50?S, 70°30? to 70°10?W), San Juan, Argentina was made. The study area comprises a surface of approximately 432 km2 (50% above 3500 m asl); 15 rockslides, 12 complex rockslides evolving to rock avalanches and 19 rock avalanches were identified. The deposits were analysed with remote sensory imagery and during fieldwork in order to study processes under permafrost degradation caused by global warming. Rock sampling procedures and laboratory rock-resistivity testing were also carried out. The characterization of the detachment scars and the deposits for two rockslides was performed. Two different mechanisms were identified. In one rockslide the shallow active layer detachment was favoured by the shear-displacement along pre-existing joints, as a result of short-term climatic warming periods. In the other, a long-term permafrost degradation in rockslide, favoured a deeper failure process. The studied landslide processes should not be explained by the permafrost degradation factor alone. Faults, the geometric arrangement of their structural elements and seismic activity may contribute to trigger these phenomena. It is expected that the magnitude and frequency of rockslide hazards will increase during the 21st century.