has evaporation, which currently removes almost 5/6 of the total inflow. A pumice fall deposit of dacitic composition is associated with the sector collapse event, which together with lava bombs suggest that an eruption took place at the time of the collapse; this has been contested however. The sector collapse was probably not caused by an eruption, although the intrusion of a cryptodome may have helped. There is no evidence on the edifice for the existence of a collapse scar, indicating that post-collapse volcanic activity has completely filled up the space removed by the collapse. The volcanic edifice has reached a volume similar to its volume before the failure. Surroundings The terrain around Parinacota is mostly formed by Neogene volcanic rocks. These are for the most part over one million years old and include individual volcanic centres such as Caldera Ajoya, Caldera Lauca, Choquelimpie, Condoriri, Guane Guane, Larancagua and Quisiquisini, and the Miocene Lauca ignimbrite (2.7 ± 0.1 million years ago) that forms the basement. The activity of many of these centres occurred over 6.6 million years ago. At slightly larger distances lie the volcanoes Guallatiri, Nevados de Quimsachata and Taapaca. Proterozoic and paleozoic basement rocks crop out as charnockite/granulite east and as amphibolite/gneiss west of the volcano, respectively. Other formations include the volcaniclastic Lupica Formation of Oligocene-Miocene age and the lacustrine Lauca formation. A number of volcanoes have been active around Parinacota in the last one million years. Pomerape northeast of Parinacota is similar to Parinacota but the greater degrees of erosional decay suggest it is older than Parinacota; a subsidiary vent dated 205,000 years ago is found on its eastern slope. Pomerape is a comparatively simple volcanic cone whose foot is covered by glacial debris. One age obtained on the cone is 106,000 ± 7,000 years ago. The Caquena and Chucullo rhyolitic to andesitic lava domes are found northwest and southwest of Parinacota, respectively; they are associated with the oldest stages of activity at Parinacota. Periglacial and erosional landforms Periglacial landscapes are frequent in the area; they include rounded landforms, smooth surfaces, solifluction terrain and striated terrain. This extensiveness is the result of the relatively dry climate in the region, which limits the development of glaciers. On Parinacota, landforms of this type are found starting from elevation and become dominant above until the glacier line. The extent of their development is a function of the age of the