Crater lake inside Santa Ana volcano.
Santa Ana is the dominant volcano of western El Salvador. It is a stratovolcano composed of a large central vent characterized by a flat and almost circular crater of 1.5 km in diameter. It has suffered four collapses, during which, the main vent has migrated to the southeast. In the innermost crater (0.5 km in diameter) lies a small acid crater lake and high temperature fumaroles which produce the native sulfur that gives an emerald green color to the lake waters.
Aerial photo of Santa Ana crater, showing collapse benches and active vent. Michael Carr, 1982.
A NW-SE fault system dissects the crater forming a graben-like structure in it. This fault trend extends nortwest to the town of Chalchuapa (approximately 15 km away)and along these faults several cinder cones, explosion craters and lava flows have been formed. Southeast of the Santa Ana volcano, Izalco, Cerro Verde and several minor eruptive centers lie on an extension of the NW-SE fault system.
Directly east of the Santa Ana volcano, starting from an alevation of approximately 1500 m, a very steep subcircular escarpment forms the walls of the Coatepeque collapse caldera. West of the crater the morphology of volcano suggests the existence of an edifice collapse scar, that is believed to have produced an avalanche debris that covered approximately 200 km2 and formed the Acajutla peninsula to the south.