The Las Cumbres volcanic complex, a Quaternary center about 15 km NNE of Pico de Orizaba, contains a 3.5-4.5 km wide summit caldera narrowly breached on the east side. A dacitic lava dome (Cerro Gordo or El Cumbre Grande) lies in the center of the caldera. A group of monogenetic cones, explosion craters, and andesitic and rhyolitic lava domes is located north and south of Cerro las Cumbres. Three of these, Xalista and El Rodeo to the north, and Ixetal to the south, are obsidian domes. A major rhyolitic explosive eruption producing the Quetzalapa Pumice about 20,000 years ago originated from a vent on the lower NW flank of the Las Cumbres complex. Eruptive activity at the main Las Cumbres complex ceased during the late Pleistocene, although activity on the flanks of the edifice continued into the Holocene. The rhyolitic Yolotepec lava dome, north of Las Cumbres, has been radiocarbon dated at about 5900 years before present.