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The role of hydroclimate on magma-water interactions at hydraulically-charged ocean island volcanoes

Mariana Andrade1,2, Armand Hernández3, Ricardo S. Ramalho4,2, Adriano Pimentel5, José Virgílio Cruz5, Alexandre Ramos6,2, Julie Christin Schindlbeck-Belo1

  • Affiliations: 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany. 2 IDL - Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal. 3 Universidade da Coruña, GRICA Group, Centro Interdisciplinar de Química e Bioloxía (CICA), Rúa as Carballeiras, A Coruña 15071, Spain. 4 School of Earth and Environmental Sciences, Cardiff University, Park Place, Cardiff CF10 3AT, United Kingdom. 5 Instituto de Investigação em Vulcanologia e Avaliação de Riscos (IVAR), Universidade dos Açores, Ponta Delgada, Azores 9500-321, Portugal. 6 Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany.

  • Presentation type: Poster

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

  • Poster Board Number: 179

  • Programme No: 3.3.15

  • Theme 3 > Session 3

Abstract

The interaction of ascending magma with groundwater or surface water may produce phreatomagmatic explosions that, due to their violence and unpredictability, may increase the hazard potential of an eruption. To investigate the link between groundwater variations and phreatomagmatism, we analysed the volcanic record of Flores Island (Azores), which includes several monogenetic magmatic and phreatomagmatic eruptions in the last 300 kyrs, together with local and regional climate reconstructions. Our results show that in the long term (>10 kyrs), magmatic eruptions dominated during dry/colder periods, while phreatomagmatic volcanism occurred predominantly in wet/warmer periods. In the short term (<10 kyrs), magma-water interactions were controlled by variations in eruption rates, which allowed water to access the active conduits/craters.  Accordingly, rainfall variability had a secondary role given that groundwater remains ubiquitously available in this setting, even in periods with lower precipitation. Here, we confirm that on island volcanoes under heavy rainfall conditions and with permanently charged shallow groundwater bodies, variations in magma output rates of monogenetic eruptions, rather than short-term hydroclimate variations, trigger phreatomagmatism and consequently increase volcanic hazard.