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Unravelling Pleistocene-Holocene Plinian eruption hazards and dynamics from detailed lithostratigraphy, radiocarbon dating, and chemical-microtextural analyses at Pico de Orizaba Stratovolcano and Los Humeros Caldera, Eastern Mexico

Rafael Torres-Orozco 1, José Luis Arce2, Matías Vázquez-Montoya3,4, Gerardo Carrasco-Núñez5, Katrin Sieron6, Francisco Córdoba-Montiel1

  • Affiliations: 1Centro de Ciencias de la Tierra, Universidad Veracruzana, Xalapa, Veracruz, Mexico; 2Instituto de Geología, Universidad Nacional Autónoma de México, Mexico City, Mexico; 3Programa de Maestría en Ciencias de la Tierra, Universidad Veracruzana, Xalapa, Veracruz, Mexico; 4Now at: School of Science and Technology, Geology Division, Universitat di Camerino, Camerino, Italia; 5Instituto de Geociencias, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, Mexico; 6Landesamt für Bergbau, Geologie und Rohstoffe Brandenburg (LBGR), Geological Survey, Cottbus, Germany

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 121

  • Programme No: 3.4.11

  • Theme 3 > Session 4

Abstract

The most intense explosive volcanism in eastern Mexico spans from the Pleistocene to the Holocene and includes recent activity (1700-1800 CE and 2.8 ka, correspondingly) from the andesitic-dacitic Pico de Orizaba Stratovolcano (PO, 5630 m-altitude) and the basaltic-rhyolitic Los Humeros Caldera (LHC, 2800 m-altitude). These two systems have complex eruptive histories, featuring stages of numerous Plinian events bounded by episodes of edifice-collapse-driven debris-avalanches (PO) and caldera-collapse-driven ignimbrites (LHC). While the rare collapse stages are well-documented, the more frequent inter-collapse explosive eruptions and associated hazards are less understood. We conducted comprehensive lithostratigraphic mapping, radiocarbon dating, and chemical and microtextural analyses to reconstruct the eruptive source parameters, intensities, magnitudes, hazards, and dynamics of three of the largest Plinian episodes from PO and LHC. Our findings indicate that PO can produce VEI-4 Plinian eruptions with column heights of 25-28 km, fall deposits of 0.04-0.1 km3 dense rock-equivalent (DRE), and mass discharge rates of 108 kg/s. In contrast, LHC is capable of catastrophic VEI-6 Plinian eruptions with column heights reaching 35-40 km, fall deposits of 1-5 km3 DRE, and discharge rates of 108--109 kg/s. In both systems, Plinian columns are interspersed with pyroclastic density currents driven by summit dome-collapse (PO), outgassed lava-plug explosions (LHC), column-collapse, or hydromagmatic processes. Microtextural and chemical analyses of banded PO scoria and LHC pumice clasts suggest that magma mixing or mingling commonly powers explosive volcanism in eastern Mexico. In the event of reactivation, these systems could threaten up to two million people.