San Cristobal is part of a five-volcano complex of the same name and is the most active of the five. It erupted in 1997 for the sixth time since it was discovered long ago. It's close to the cities of El Viejo and Chinandega but its long 10 km lava flows never reach them. Like most volcanoes in Nicaragua, San Cristobal is a stratovolcano. It has a basaltic cone with a flattened top and the cone is made up of alternating lava and tephra. Several smaller cones have formed at the base of the volcano with a single vent leading up to each.