Late formative flooding of Izapa after an eruption of Tacaná volcano

Between the years of 30 b.c. to a.d. 80, during the Late Formative period, the site of Izapa was flooded by lahars associated with an explosive eruption of the San Antonio volcano (part of the Tacana Volcanic Complex). Computer simulations suggest that hot pyroclastic flows did not impact Izapa directly, but did impact the region considerably, filling and clogging the Cahuacan and Mixcun rivers with hot debris. The material was quickly saturated by heavy rains and, as the water from the rivers overtopped the obstruction, remobilized in the form of a hot mixture of mud and water known as a lahar (or flood of volcanic origin), which flowed down through the piedmont zone along the Cahuacan, Mixcun-Suchiate, and Izapa rivers. At Izapa, the flood took the form of a 6-m catastrophic wave of mud and water that likely destroyed crops and caused many causalities, surrounding the architectural mounds at Izapa with a muddy landscape. The floods also dramatically affected the rivers downstream, undoubtedly wreaking serious damage to the transport and trade of goods along the coast.