Pirineos, 145-146: 3 5 a 63, JACA; 1 995 THE INFLUENCE OF THE GEOMORPHOLOGIC HERITAGE ON PRESENT SLOPE DYNAMICS. THE CREDOS CIRQUE, SPAIN Julio MUÑOZ, David PALACIOS and Javier DE MARCOS Department of Physical Geography. Universidad Complutense. 28040 MADRID, ESPAÑA. ABSTRACT.- Sierra de Gredos ¡s the highest mountain range in the Sistema Central which crosses the Iberian Peninsula from vwest 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 geomorphologichistoryoftheCirque. In addition, it studies the accumulation and permanence of the nival slope cover, as the fundamental source of \A/ater, 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 géomorphologie 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, wth the exception ofthe higher average temperatures, especially in summer, thesame 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. RESUMEN: La investigación se llevó a cabo en la cabecera de un valle en un área de origen glaciar: Circo de Gredos, situado en la cara Norte de la Sierra de Gredos (Sistema Central) a 40 ° de latitud Norte, bajo su pico más alto (Almanzor, 2592 m de altitud). Este trabajo analiza los diferentes paisajes y deduce a partir de ello la historia geomorfológica del Circo. Además, se estudia la acumulación y permanencia de la cubierta nival, como fuen te fundamen tal de agua, principal agente actualmente de la erosión. Las conclusiones muestran la relación entre sedimentos antiguos y la distribución del manto meteorizado y la capacidad efectiva de la actividad erosiva actual en las laderas. Como resultado de este trabajo se propuso un modelo de dinámica de vertientes para áreas glaciadas en la península Ibérica. De acuerdo con este 35 (c) Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España (by-nc) http://pirineos.revistas.csic.es