Integrated hazards maps of the Tacaná Volcanic complex, Mexico-Guatemala: Ashfall, block-and-ash flows, and lahars

Abstract

The Tacaná Volcanic Complex (TVC) is an active volcano, located on the border between Mexico and Guatemala, in the westernmost part of the Central American Volcanic Arc. The TVC has produced effusive and explosive activity during the past 300 ka through the emplacement of lava flows, pyroclastic deposits, debris avalanches and lahars. During the last 10 ka, at least 11 eruptions have occurred, with three small phreatic explosions documented in 1855–1856, 1949 and 1986. This work presents volcanic hazards maps of the TVC that integrate the results of analyzing two eruptive style scenarios: dome-collapses and Plinian-type eruptions and the lahars triggered by both these hazards. The extents and expected distributions for each of these phenomena were assessed using numerical models and the results were calibrated with recent field data. The simulation results were merged to prepare three new volcanic hazards maps, which depict on a color scale the hazard level forecasted for each phenomenon (high – red, moderate – orange, and low – yellow). The maps show that the total extension of block-and-ash flows will be restricted towards the volcano base, reaching a maximum distance towards Guatemala of ~5 km, and ~10 km in Mexico; while lahars could reach up to 50 km downstream along the main rivers that drains the complex (i.e. Coatán, Cahoacán and Suchiate rivers) that would flood important urban centers mostly over Mexican territory. Ashfall would cover an area of ca. 8000 km2, inhabited by ~2 million people in both countries. Hence, renewed eruptive activity of the TVC would be catastrophic not only because of the loss of human life but also for its adverse impact on economic activity based on corn, coffee, and banana plantations, together with the disruption of communication and transportation systems between Mexico and Central America.