Abstract

Flank collapses are one of the most significant destructive processes in long-lived volcanoes, resulting in debris avalanche deposits (DADs), which shed light on volcanic landslide sizes, physical characteristics, and transport mechanisms. Here, three DADs with a hummocky topography recognized at Ollagüe, a long-lived and mainly effusive volcano in the Central Volcanic Zone of the Andes, are investigated in detail. We combine fieldwork and morphometric analysis to characterize the DADs, constrain the destabilization and trigger factors, and determine the effect of the substrate on the emplacement of the debris avalanches. In general, hummocks decrease in size, volume, and competence with distance. The low rate of size decrease, large runout distances, and spatial distribution of hummocks suggest a high mobile flow in proximal parts (recorded by a non-depositional belt lacking hummocks) followed by a more distal sector marked by rapid deceleration of the avalanche, directly attributable to the combined effects of topography and substrate nature, with a passage from a shallow paleolake to a dry and non-competent evaporitic substrate (salt flat) in correspondence with the Carcote Basin. This study provides further insights into the effect of weak ductile substrates on debris avalanche transport and emplacement mechanisms, with DADs from Ollagüe revealing a complex dynamic interplay between the evolution of the volcano and the surrounding landscape, reflected by fluctuations in the level of the Carcote paleolake. © Springer-Verlag GmbH Germany, part of Springer Nature 2025.