Archaeological evidence suggests that Teotihuacan was a multi-ethnic city, and while the official languages used by Teotihuacan is unknown, Totonac and Nahua, early forms of which were spoken by the Aztecs, seem to be highly plausible. This apparent regionally diverse population of Teotihuacan can be traced back to a natural disaster that occurred prior to its population boom. At one point in time, Teotihuacan was rivaled by another basin power, Cuicuilco. Both cities, roughly the same size and hubs for trade, both were productive centers of artisans and commerce. Roughly around 100 BC however, the power dynamic changed when Mount Xitle, an active volcano, erupted, and heavily impacted Cuicuilco and the farmland that supported it. It is believed that the later exponential growth of Teotihuacan's population was due to the subsequent migration of those displaced by the eruption. While this eruption is referenced as being the primary cause for the mass exodus, recent advancements of dating have shed light on an even earlier eruption. The eruption of Popocatepetl in the middle of the first century preceded that of Xitle, and is believed to have begun the aforementioned degradation of agricultural lands, and structural damage to the city; Xitle's eruption further instigated the abandonment of Cuicuilco.