Xico is a low circular tuff ring within Mexico City that is part of the Chichinautzin volcanic field. It is seen here in an aerial view from the south. This volcano was formed by phreatomagmatic eruptions through the middle of Lake Chalco, whose remains can be seen surrounding the tuff ring. Chalco and Lakes Texcoco and Xochimilco were formed when lavas from the Chichinautzin volcanic field blocked river drainages to the south. The lakes were largely drained during the 16th and 17th centuries following the Spanish conquest.
Photo by Hugo Delgado, 1994 (Universidad Nacional Autónoma de México).