Internal structure and behaviour of a rock glacier in the Arid Andes of Argentina

This paper reports results of the application of combined refraction and geoelectric geophysical methods to the study of the El Paso rock glacier in the arid Andes of Argentina. The data allow inferences to be made upon the internal structure, and permafrost thickness of the rock glacier. The El Paso rock glacier is located in the arid to hyper‐arid Agua Negra basin. Due to its altitude, it records some of the world's highest global radiation. The active layer thickness was studied using refraction seismic methods. Seasonal monitoring of this layer showed large variations in thickness, being thicker in summer and thinner in winter. Geoelectric methods allowed detection of a wet layer underlying permafrost, thereby providing information about the character of the rock‐glacier base. The maximum inferred thickness of El Paso permafrost was 18.5 m. Three main layers were detected: an upper deposit of dry debris over a debris‐water layer, a debris‐ice‐mixture (i.e. permafrost), and a lower one composed of wet debris. The geophysical results permit a first estimate of the volume of water (6.3 hm3) enclosed in the rock glaciers of this region, indicating that locally, rock glaciers are important water resources. However the incidence of water availability to the arid lowlands is unknown. Copyright © 2002 John Wiley & Sons, Ltd.