 The best-known eruption occurred about 1670 radiocarbon years ago from the Xitle scoria cone, NE of the Volcán Ajusco lava-dome complex, which at forms the highest peak of the Sierra Chichinautzin.The Xitle eruption produced a massive basaltic tube-fed lava flow that covered agricultural lands as well as pyramids and other structures of Cuicuilco and adjacent prehispanic urban centers.The southern part of Mexico City and the National University of Mexico, in the greater "El Pedegral" district, lie atop the distal end of the long lava flow.