 The caldera contains a resurgent dome, whose highest point in the frost-shattered Galán massif reaches an elevation of about .Seismic tomography has identified a slow-speed anomaly beneath Galán, which has a volume of about and is considered to be a magma reservoir of the volcano.Summits along the caldera margin include Cerro Aguas Calientes to the north, Cerro Leon Muerto to the southeast, Cerro Pabellon to the southwest and Cerro Toconquis to the northwest.