The collapse of the caldera cut through older volcanic centres, exposing the Ceja Alta and Quilapana porphyry deposits. Other older volcanic centres exposed in the walls of the caldera are the Cerro Aguas Calientes stratovolcano in the eastern wall and the Cerro Gigantes in the western wall. Volcanic activity resumed within the caldera and at the edge of the resurgent dome, forming lava domes between 4.1 and at least 1.6 million years ago. These volcanic centres include the Corral de Coquena crater and the lava domes of Morro Negro east, Cerro Bola and Purifican west and Cerros de Guayaques north of the resurgent dome. The Arenoso, Chamaca and Chivato Muerto lava domes in the southern wall of the caldera were originally considered to be pre-caldera; later these three domes were identified as post-caldera domes. Stratovolcanoes inside the caldera include the cones associated with the Cerros de Guayaques lava domes and the volcanoes Cerro Incaguasi, Cerros de Pili, Cerros Negros and Huailitas.