Date of Award

2025

Document Type

Open Access Master's Thesis

Administrative Home Department

Department of Geological and Mining Engineering and Sciences

Advisor 1

Simon A. Carn

Committee Member 1

Greg Waite

Committee Member 2

Chad Deering

Abstract

Volcanic eruptions release large quantities of gases, including sulfur dioxide (SO₂), aerosol precursors, and ash into the atmosphere. Quantifying the emission fluxes and temporal variability of SO₂ is crucial for understanding volcanic processes and assessing their impacts on air quality, climate, and aviation safety. Episodic vulcanian to sub-Plinian explosive eruptions are a common feature of many arc volcanoes, but the underlying causes of such episodic behavior remain poorly understood. The 2021 La Soufrière eruption (St. Vincent) featured up to 40 discrete eruptive events between April 9 and April 22, presenting a rare opportunity to analyze time-resolved volcanic SO₂ emissions during a period of episodic explosive volcanism. In this study, we use ultraviolet (UV) satellite observations from the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR) to track and quantify SO₂ emissions from individual explosions during the 2021 La Soufrière eruption. High-cadence EPIC imagery captures short-lived SO₂ plumes, complementing spatially detailed but temporally limited observations from the TROPOspheric Monitoring Instrument (TROPOMI) on the polar-orbiting Sentinel-5P satellite. SO₂ plumes observed by EPIC are further analyzed using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. By combining forward and backward trajectory simulations with satellite data, we estimate plume injection heights ranging from 15 to 21 km and confirm the volcanic origin of each detection and stratospheric injection of volcanic SO2. Pixel-level SO₂ mass estimates derived from EPIC and TROPOMI reveal substantial variability across events and highlight the sensitivity of mass retrievals to assumed plume height. TROPOMI-derived mass values (~380–840 kt) exceed those published by Esse et al. (2023) for the same days, reflecting differences in spatial coverage and retrieval methodology. EPIC SO2 measurements provide constraints on waning SO2 emissions during the later stages of the La Soufrière eruption (April 11-13) that were unavailable from TROPOMI. This study demonstrates the value of multi-sensor integration and trajectory modeling in capturing the dynamics and strength of explosive SO₂ emissions, with implications for hazard monitoring and atmospheric impact assessments.

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