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Combining Ash Characteristics, Geophysical Data, and Visual Observations to Understand the 2022 Eruption of San Miguel Volcano, El Salvador

^1^Dennis Lemus,^^ 2Christopher Harpel, 1Valeria García, 3David Damby, 4Alexa Van Eaton, 1Jacqueline Rivera, 1Francisco Montalvo, 1Cecilia Polío and 1Miriam Villalobos.

  • Affiliations: 1. Ministry of Environment and Natural Resources of El Salvador 2. U.S. Geological Survey, Volcano Disaster Assistance Program, Cascades Volcano Observatory, USA 3. U.S. Geological Survey, Volcano Science Center, Moffett Field, USA 4. U.S. Geological Survey Cascades Volcano Observatory 

  • Presentation type: Poster

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

  • Poster Board Number: 83

  • Programme No: 3.16.10

  • Theme 3 > Session 16

Abstract

After its 2013 Volcanic Explosivity Index (VEI) 3 eruption, San Miguel volcano has experienced several minor eruptions (VEI 1--2) in subsequent years. One of the most notable occurred from November 15--29, 2022, with more than 190 small Vulcanian eruptions, accompanied by ash emissions and ejected ballistics. Analysis of ash samples collected during the eruption sequence, along with geophysical and visual data, provide insights into this activity. In the months before the crisis, seismic activity was anomalous, particularly episodes of tremor a month before and low-frequency earthquakes in the days prior to the eruptions. However, GPS and INSAR did not record any deformation of the volcano. Seismicity and the absence of deformation could indicate a semi-open or open conduit volcanic system. Ash characteristics reveal the presence of juvenile material, with black, vesicular, angular, and shiny clasts, and golden vesicular clasts, indicating that the eruptions involved fresh magma. Towards the end of the crisis, a change in componentry was observed with a decrease in free crystals and increase in altered angular black material, coinciding with a rise in explosiveness, reaching the maximum heights of the eruptive columns. Volcanic ash fell in nearby communities and for the first time, the impacts on health and the environment were assessed. Approximately 20% of the ash volume sampled on different days contained respirable-sized particles (<10 microns). Furthermore, leachate data from the ash were collected to assess the impacts on water sources for human and animal consumption, as well as on crops in the area.