by the collapse. A structure named Domo del Núcleo in the scar may either be a remnant of the pre-collapse volcano, or collapse debris. A similar collapse was observed in the 1980 eruption of Mount St. Helens. In fact, the occurrence of a large landslide at Mount St. Helens probably aided in the subsequent identification of the Socompa deposit as a landslide remnant. Other volcanoes have suffered from large scale collapses as well; this includes Aucanquilcha, Lastarria and Llullaillaco. In the case of Socompa, the occurrence of the collapse was probably influenced by a northwest tilt of the basement the volcano was constructed on; it caused the volcano to slide downward in its northwestern sector and made it prone to a collapse in that direction. The collapse happened about years ago, it was not witnessed in historical records. This event probably lasted only 12 minutes based on simulations. The growth rate of the volcano increased after the collapse, probably due to the mass removal unloading the magmatic system. There is evidence in the collapse deposit that a lava flow was being erupted on the volcano when the landslide occurred, which together with the presence of pyroclastic fallout on the southwestern side of Socompa implies the collapse may have been started by volcanic activity. The quantity of water in the edifice rocks on the other hand was probably minor. Another theory assumes that the volcanic edifice was destabilized by ductile and mechanically weak layers beneath Socompa; under the weight of the volcano these layers can deform and "flow" outward from the edifice, causing the formation of thrusts at its foot. Evidence of such spreading of the basement under Socompa has been found. The collapse generated a large amount of energy, about . Some evidence in the form of tephra suggests that the collapse was accompanied by a lateral blast, but other research found no such evidence. Such sector collapse events are catastrophic phenomena, and the debris avalanches associated with them can reach large distances from the original volcano. The fragmentation of rocks during the landslide and the fine material generated during this process might enhance the fluidity of the avalanche, allowing it to extend far away from the source. Landslide deposit The collapse deposit covers a surface area of , and is thus not as large as the deposit left by the Mount Shasta collapse or by the Nevado de Colima