The magma chamber of Lascar appears to lie at depths of , although the lack of deformation of the edifice during the 1993 eruption indicates that it may be deeper, over or even over deep. There appear to be two distinct chamber systems, an andesitic one that is responsible for the frequent andesite lava and pyroclastic flow activity, and a dacitic one that was involved in the Piedras Grandes and Soncor activities.