The influence of the géomorphologic heritage on present slope dynamics. The Gredos Cirque, Spain

Abstract

Sierra de Gredos is the highest mountain range in the Sistema Central which crosses the Iberian Peninsula from west to east at a latitude of 40° N. Research \A/as carried out at the valley head of an area of glacial origin -Gredos Cirque-, situated on the northern side of this range, below its highest peak -Almanzor, which is 2,592 m in height. This work analyzes the different landforms, and infers from them the Geomorphologic history of the Cirque. In addition, it studies the accumulation and permanence of the nival slope cover, as the fundamental source of water, the main present agent of erosion . The conclusions show the relationship between old sediment and weathered mantle distribution and the effective capacity of present erosive activity on slopes. As a result of this work, a model of slope dynamics for glaciated areas in the Iberian peninsula has been proposed. According to this model, the Pleistocene glaciers accentuated a significant geomorphology asymmetry between eastern and western slopes of valley heads. The present snow distribution patterns mirror those during the Pleistocene. Although snow amounts are obviously significantly lower, it is the present principal agent erosion and is accentuating this contrast. This is because, with the exception of the higher average temperatures, especially in summer, the same Pleistocene system of snow accumulation is continuing. This model will enable research work to be initiated in present dynamic Gredos Cirque, where it has never been carried out before.