Challenges of determining frequency and magnitudes of explosive eruptions even with an unprecedented stratigraphy

Abstract

Abstract Through decades of field studies and laboratory analyses, Volcán de Colima, Mexico has one of the best known proximal eruption stratigraphies of any volcano, yet the frequency and magnitudes of previous eruptions are still poorly resolved. Hazard assessments based on models of well-known, well-mapped recent eruptions may appear to have low uncertainty, but may be biased by the nature of those events. We present a comprehensive stratigraphy of explosive eruption deposits combining new data collected as part of this study together with published and unpublished data. For the first time we have been able to model five of the best exposed and cross-correlated pre-historical Holocene explosive events at Volcán de Colima. By modelling the volumes and magnitudes of Holocene eruptions at Volcán de Colima, we are able to improve estimations of the potential range of magnitudes of future explosive eruptions, which can be incorporated into hazard assessments for nearby communities. Based on recent studies we demonstrate that these volumes may be underestimated by at least an order of magnitude, and show that even with an exceptionally well-defined stratigraphic record our understanding of the full range of explosive eruptions may still be biased.

Keywords

• Volcán de Colima
• Tephra dispersion modelling
• Hazard assessments
• Tephra stratigraphy
• Eruption frequency
• Eruption magnitude