Approximately 296,000 km2 of western Mexico is covered by a volcanic sequence that has an average thickness of 1 km and is mostly ash-flow tuff. Although some 350 calderas are suggested by this tremendous volume, only a few have been located or described. In the state of Durango the only well documented examples are in the 30-Ma old Chupaderos caldera complex near Durango City. Although the complex is mostly covered by Quaternary basalt and sediment, the exposed portion reveals nested calderas that produced two major rhyolitic ash-flow tuffs.