Cerro Chao is a -long coulee. It has a volume of and its flow front is high. Based on volumetric considerations, the eruption lasted about 100-150 years with an average lava flux rate of . The volume of Chao is exceptional for a lava dome structure, although the lava flux rate generating it is low in comparison to a basaltic eruption like Laki in Iceland. This low flux rate is insufficient to cause caldera formation. Cerro Chao is the largest Quaternary silicic lava flow in the world. The vent location is related to an inferred fault zone emanating from one of the neighbouring volcanoes.