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The Caquella rock glacier (5960-5400 m ASL), approximately one kilometre long, is an important active rock glacier in the intertropical zone. In the arid high mountain environment of Bolivia, glaciers are absent. Rock glaciers represent, with salt lakes, the best indicators of climate variability. Moreover, they act as water reservoirs in the present hydrological cycle in which precipitation is very low. Direct observations and geoelectrical soundings make it possible to identify interstitial ice in the permafrost. Nevertheless, the resistivity curve profile, the ice distribution in the debris mass as well as observations from the surface topography provide clear evidence that this rock glacier is in a degradation phase. The Caquella rock glacier 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 degradation have occurred during this century. Copyright (C) 1999 John Wiley & Sons, Ltd.