evidence: Photo by José Macías, 1995 (Universidad Nacional Autónoma de México). Popocatépetl volcano is seen here to the south from the Iztaccíhuatl summit ridge. Unlike the eroded Iztaccíhuatl volcano, which has been infrequently active during the Holocene, Popocatépetl has been vigorously active. [...] Photo by Hugo Delgado-Granados, (Universidad Nacional Autónoma de México). The N-S-trending Popocatépetl-Iztaccíhuatl volcanic chain lies between the Valley of Mexico and the Puebla basin. Snow-capped Iztaccíhuatl volcano lies just above the center of the image. The city of Texmelucan can be seen at the upper right. Across the Paso de Cortés from Iztaccíhuatl is steaming Popocatépetl volcano, located SE of the city of Amecameca (mid-left margin). A voluminous prehistorical lava field from Popocatépetl forms the forested lobe extending about 20 km down the eastern flank at the lower right. [...] Photo by Juan Manuel Espíndola, 1991 (Universidad Nacional Autónoma de México). Iztaccíhuatl (left) and Popocatepetl (right), two of the highest volcanoes in Mexico, are seen from the SW on a rare smog-free day. The morphology of Iztaccíhuatl is due to multiple vents across the summit region . Fresh snowfall at Popocatepetl covers periodic ashfall deposits.