The Cuicuilco Pyramid in Mexico is another enigma. It was geologically dated to before 8,500 BC based upon the fact that it existed before the first volcanic eruption of Mount Xitli.regarding that...
Gods, Graves, and Scholars: The Story of ArchaeologyNow, several of these pyramids located at different sites from Tula to Monte Alban have been discussed, yet one of the most important has yet to be mentioned. This is the Pyramid of Cuicuilco, which stands on a mound 22.4 feet high, situated at the southern limits of Mexico City. The Pyramid of Cuicuilco rises up out of a weird landscape of darkly stony aspect. At one time the volcanoes Ajusco and Xitli (perhaps only the latter) erupted. The god within the pyramid was apparently remiss in diverting the glowing flood of lava that flowed about the pyramid, for half the structure was drowned in bubbling muck. The archaeologists investigating this phenomenon called on colleagues from another faculty, the geologists, for help. How old is the lava, they inquired. The geologists, not realizing that their answer was knocking a world picture awry, answered: "Eight thousand years." ...Yet late research is more inclined to consider it false.
by C. W. Ceram