Symptoms of degradation in a tropical rock glacier, Bolivian Andes

The Caquella rock glacier (5960-5400 m ASL), approximately one kilometre lo ng, is an important active rock glacier in the intertropical zone. In the a rid high mountain environment of Bolivia, glaciers are absent. Rock glacier s represent, with salt lakes, the best indicators of climate variability. M oreover, they act as water reservoirs in the present hydrological cycle in which precipitation is very low. Direct observations and geoelectrical soun dings make it possible to identify interstitial ice in the permafrost. Neve rtheless, the resistivity curve profile, the ice distribution in the debris mass as well as observations from the surface topography provide clear evi dence that this rock glacier is in a degradation phase. The Caquella rock g lacier probably originated in the early Holocene. The presence of a recent moraine in the upper part suggests that the ELA lowered to the rock glacier surface during the Little Ice Age. The climatic conditions producing the d egradation have occurred during this century. Copyright (C) 1999 John Wiley & Sons, Ltd.