The newly discovered Aliso volcanic complex lies at the eastern foot of the Ecuadorian Andes, east of Antisana volcano and SW of the town of Baeza. The largely unexplored complex contains an arcuate summit ridge on the west with older andesitic lava flows and tundra-like vegetation, and rhyolitic and dacitic lava domes in a wet cloud-forest environment on the lower eastern flanks. The Pumayacu center on the SE flank contains several lava domes along a NNE axis parallel to the Andean Thrust Fault System (TFZ). Morphologically young andesitic lava flows occur along the flat-topped ridge above Baeza town. The Pumayacu center erupted pyroclastic-flow deposits of late Pleistocene and Holocene age. One pyroclastic-flow deposit was dated at about 4400 years Before Present, and a pumice lapilli layer overlies a ceramic-rich cultural horizon thought to be about 2000 years old.