The cerro caquilluco–cerrillos Negros Giant rock avalanches (Tacna, Peru)

Abstract

Giant rock avalanches have been recognized and mapped in southern Peru, to the N of Tacna. The Cerro Caquilluco rock avalanche complex has a total volume of about 15 km3 and a length of 43 km, extending from 3,900 to 530 m a.s.l. Mapping the internal structures, the scar features and the depositional lobes allowed to suggest that the rock avalanche complex developed as a sequence of successive failures affecting tuffaceous and conglomeratic formations forming a gently dipping monoclinalic slope. Assessment of lobes volume constrained the reconstruction of the source areas for the multiple failures and the successive rock avalanche simulations. Seismic triggering is suggested, whereas H/L vs volume relationships suggest a high mobility comparable to that of extremely mobile volcanic rock avalanches. .