Cofre de Perote (Nauhcampatepetl) volcano lies at the northern end of the Citlaltepetl-Cofre de Perote volcanic range (CCVR) that is the easternmost of several volcanic chains orthogonal to the E-W trend of the Trans-Mexican Volcanic Belt (TMVB). The CCVR is an important physiographic feature separating the Gulf coastal plains from the Altiplano, with pronounced differential relief of more than 1000 m and sloping substrate promoting major edifice failures toward the Gulf of Mexico coastal plain of most of the volcanoes that form that chain. Its structure, composition, and volcanic history diverge significantly from that of the large dominantly andesitic stratovolcanoes that have been the major focus of research efforts in the TMVB. Cofre de Perote volcano is dominated by the successive emplacement of basaltic andesite, andesitic-trachyandesitic to dacitic lava flows and associated breccias erupted through different vents that built a massive low-angle compound shield-like volcano, in contrast to a typical steep stratocone. Despite that apparently stable morphology, repeated edifice collapse has left massive horseshoe-shaped scarps that truncate the eastern side of the edifice. Five major evolutionary stages characterize the growth of this volcano including: 1) emplacement of a multiple-vent dome complex forming the basal structure of Cofre de Perote around 1.3-0.51 Ma; 2) construction of the basal part of the compound shield volcano from at least two main upper-edifice vents and minor flank vents at about 0.42-0.31 Ma; 3) effusion of the summit lavas through multiple vents at 0.25-0.2 Ma; 4) late-stage, large-volume edifice collapse on at least two occasions (ca. 40 ka and ca. 11-13 ka), producing long-runout debris avalanches and debris flows that traveled to the east; and 5) nearly simultaneous eruption of both alkaline and calc-alkaline Pleistocene-to-Holocene monogenetic cones (likely related to regional volcanism) through the flanks of the Cofre de Perote edifice. Long-term factors influencing edifice failure include hydrothermal alteration, increased pore pressure from glacially derived water, extension produced by repetitive volcanism along the chain parallel to the maximum horizontal compression, and perhaps most significantly, construction of the edifice over a sharply eastward-sloping substrate. Evolution of a compound shield volcano like Cofre de Perote reveals that even relatively stable, long-quiescent edifices with a gentle morphology that are considered apparently extinct structures pose a significant hazard to the nearby populated areas, as post-eruptive sector collapses have occurred in recent times (40-11 ka) not associated with contemporaneous volcanic activity. (C) 2009 Elsevier B.V. All rights reserved.
