INTERNAL STRUCTURE, DYNAMIC BEHAVIOR AND HYDROLOGICAL CHARACTERISTICS OF A ROCK GLACIER IN THE SEMIARID ANDES OF ARGENTINA

AGOSTINA ORTIZ; CRISTIAN VILLARROEL; ANA PAULA FORTE; TAMBURINI BELIVEAU, GUILLERMO; LOTHAR SCHROTT

Conferencia; Regional Conference on Permafrost; 2021

This work aims to present the analysis of the internal structure, dynamics and hydrogeology of a large-sized, complex, multi-lobate and multi-root rock glacier located in the southwest of the San Juan province (31°52´59.75"S; 70°15´8.62"W), Central Andes of Argentina. The study was conducted combining electrical resistivity tomography (ERT), Differential Interferometry Synthetic Aperture Radar (DInSAR) and hydrochemical data. A total of 8 ERT profiles have been carried out in the El Gigante rock glacier which have been distributed to be representative for various lobes. ERT surveys shows a marked irregular geometry for the upper sector of the permafrost with electrical resistivity values ranging from 7 to 142 kΩm. This low electrical resistivity values recorded could be influenced by the high metallic concentration present in the environment, reflecting ionic enrichment to varying degrees during water circulation and subsequent re-freezing. The horizontal displacement from October 2014 to April 2017, exhibits its greatest magnitudes in the upper sector of both tongues, reaching speeds of up to 150 cm/year. The active frontal sector shows a displacement rate of 2 to 4.5 cm/year. The analysis of 28 interferograms shows minimal seasonal and inter-annual variability for the ?The Giant? rock glacier. Part of this time span corresponds to a period of extreme drought in the Andes, which directly influences the availability of water. Hydrochemical data show both the existence of different disconnected water flow pathways inside the rock glacier and the remarkable ionic concentrator effect of this landform.This study contributes to the knowledge of the material properties of rock glaciers, which represent important reservoirs/water resources, and their influence on the distribution of mountain permafrost, hydrology and dynamics. The presence of large areas of hydrothermal alteration, such as in the Andes, constitutes an additional challenge in the interpretation of cryogenic processes and a key factor in water quality.