A chain of dominantly Pliocene-to-Pleistocene volcanoes including Cerro Deslinde, Cerro Volcán, Cerros del Tatio, and Volcán Tatio is flanked on the west by a depression that contains some of the most dramatic thermal features of the Andes. Although no Holocene eruptions are known from El Tatio itself, it was included in the Catalog of Active Volcanoes of the World (Casertano, 1963) based on this geothermal activity. The 30 sq km Hoyada de Los Geisers del Tatio geothermal field contains 85 fumaroles and solfataras, 62 hot springs, 40 geysers, 5 mud volcanoes, and extensive sinter terraces. Geothermal energy exploration has been conducted, but remoteness of the location has precluded development.