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A decade of multi-parametric monitoring at Poás volcano, Costa Rica: Phreatic eruptions and Hydrothermal-magmatic interactions

Maarten de Moor 1,2, Geoffroy Avard1, Leonardo van der Laat1, Cyril Muller1, Alejandro Rodríguez1, Henriette Bakkar1, María Martínez1, Javier Pacheco1

  • Affiliations: 1Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional, Heredia, Costa Rica 2Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, USA

  • Presentation type: Talk [Invited]

  • Presentation time: Thursday 10:45 - 11:00, Room S160

  • Programme No: 3.14.2

  • Theme 3 > Session 14

Abstract

Poás volcano is one of the most active hydrothermal-magmatic systems in the world and is visited by >100,000 tourists annually. The volcano hosts an ephemeral crater lake and is prone to frequent phreatic/phreatomagmatic eruptions (>350 since 2014) with eruptive columns ranging from <50m to 4km. Geochemical and geophysical monitoring techniques used at Poás have evolved dramatically over the last decade, yielding new insights into hydrothermal-magmatic interactions and characterization of potential precursors to eruptions. Phreatic explosions are driven by magmatic degassing through a dynamic semi-permeable vent system with circulating hydrothermal fluids. Increasing gas input from shallow magma is often associated with short-term (days to weeks) precursory signals (seismicity, deformation, SO2 fluxes, gas compositions and lake changes) to eruptions. Hydrothermal sealing is thought to be an important process in priming the system for more explosive eruptions, and this process occurs slowly (months to years) and can be difficult to distinguish from quiescence. The presence or absence of the lake modifies monitoring signals and plays an important role in eruptive style, which has a direct influence on the impact of eruptive activity. Though precursors to eruptive periods are often clear in hindsight, the timing and nature of these signals varies significantly due to the complexity and dynamism of the hydrothermal-magmatic system, challenging attempts to accurately forecast eruptions. Here we will compare eruptive episodes to highlight key signals that could be useful in differentiating runup to violent eruptions from runup to mild eruptive activity at Poás and other hydrothermal-magmatic volcanoes.