A new study of tree rings has confirmed that the megadrought of the twelfth century in Mexico may have been the fatal blow to the Toltec civilization. Seventy-four core samples were taken from the Montezuma bald cypress trees in the canyon of Amealco, Querretaro, some of the longest living trees in Mexico. This ancient drought extended from the southwestern U.S. to Mexico and lasted for almost twenty years (1149-1167 AD). These samples were the first to record the climate of pre-Hispanic times.
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