Date of Award
Winter 2025
Project Type
Dissertation
Program or Major
Earth Sciences
Degree Name
Doctor of Philosophy
First Advisor
Julia G. Bryce
Second Advisor
Katharine Duderstadt
Third Advisor
Phani N. Kidambi
Abstract
This dissertation investigates the dynamics of magma storage and transport, as well as the broader implications of volcanic activity in a changing climate, with a focus on Augustine Volcano in Alaska.Chapter One extends the potential application of diffusion chronometry modeling, which has been used to determine magmatic timelines that can define – down to months and days – the pacing of magma assembly. To avoid over-prescribing boundary conditions, widespread employment of diffusion models have heretofore been restricted to applications in systems with known magma storage conditions and specific mineralogy. Limited access to operating systems or costly subscriptions to software further preclude widespread adoption of such powerful predictive methods. Here, I present a newly developed, novel approach for diffusion chronometry that seeks to meet community needs of a freely accessible, open-source model readily accessible across varied magmatic systems. The Magmatic Speedometry Using R-Fitted Elemental Diffusion (MSURFED) model provides a framework for finite difference diffusion models, with adjustable parameters that can be applied to various minerals and applications to avoid the over-prescription of storage and transport conditions. Accordingly, the application of the MSURFED model is optimal for vertically extensive systems or ones with geochemically separated magma pods. The goal of this chapter is to develop open-source models more readily accessible to a larger audience and centralize diffusion chronometry modeling in a single application available to students and researchers across the geochemical community. The second chapter applies classic petrology and geochemical methods to characterize the volcanic system of Augustine and assess how this system may have evolved over the modern eruptive life of the volcano from 1883 to 2006. Although the 2006 eruption of Augustine volcano is well studied, there are still remaining questions on how magma is stored, which directly influences how surficial signals of volcanic unrest are interpreted. Piecing together the past eruptive products from this volcano to understand the past behavior and illuminate possible constructions of the plumbing beneath the surface has the potential for greatly improving eruption forecasting. The presence of multiple crystal populations contained within each eruptive unit from 1883, 1976, 1986, and 2006 demonstrates fractional crystallization is largely driving compositional changes in the crystal cargo held within the Augustine magmatic system. Crystal populations display variable zoning patterns, both in plagioclase and pyroxene, pointing to dynamic crystallization histories influenced by repeated recharge or thermal events. Thermobarometry calculations, approached both by simulating magma crystallization pathways via alphaMELTS (Smith and Asimow, 2005; Antoshechkina and Asimow; 2010) and employing clinopyroxene-based thermodynamic models (Putirka, 2008), indicate a range of pressures, temperatures and water contents consistent with crystallization at mid- to upper-crustal depths. Geochemical data from trace and incompatible elements in groundmass glass and crystals demonstrate the mantle-derived magma source has remained relatively stable though the modern eruptive period, implying the observed variability in eruptive products arises primarily from crustal-level magma storage processing. Collectively, these results suggest that the petrologic and geochemical evolution of Augustine reflects localized heterogeneity, increasing recharge events over time, and fractionation dynamics which influenced each of the modern eruptions within a small, but compositionally complex subduction zone volcano. In the third chapter, the diffusion chronometry model methods established in Chapter 1 are applied to Augustine Volcano, with a focus on its modern eruptive period spanning from 1883 to 2006 to examine how the pacing of the magmatic system beneath Augustine has evolved over time, specifically under what conditions does the volcano erupt, and how magma storage has changed over the lifetime of the volcano. The objectives of this chapter are 1) evaluate the pacing of magma accumulation through the elemental diffusion within volcanic minerals from Augustine, 2) compare timeline reconstructions from across different eruptive periods, and 3) assessment of the vertical extent of the magma assembly by combining analyses from pyroxene, olivine, and plagioclase crystals, which crystallize at different temperatures and depths beneath Augustine. By utilizing trace elemental diffusion, this research provides insights into the timing of magmatic evolution and reveal insights into temporal patterns of magma transport and storage beneath Augustine. The results of this chapter reveal that the two different mineral phases illuminate various sections of the magmatic system. Warm storage conditions, with higher temperatures and longer residences times and recorded in pyroxenes which are stored deeper crust but with time, show a move towards lower temperatures and shorter temperatures which are more consistent with cold storage conditions. Unlike the pyroxene, the plagioclase consistently is dominated with cold storage conditions with short timescales which lengthen over time from 1883 to 2006. This suggests that as the repeated injections of new magma become stalled within the crust, the crystals continue to grow (increasing the residence time) until they are eventually cleared away by another recharge event and ultimate eruption. The final chapter explores the impact of climate change on the dispersal of volcanic ash from Augustine Volcano, with a particular emphasis on how a destabilized jet stream influences ash transport. Global climate change, notably manifested in the rapidly warming Arctic, is altering the temperature and pressure gradients in the atmosphere, affecting the speed, shape, and intensity of the Jet Stream. These shifting dynamics of the Northern Hemisphere Polar Jet Stream will control future volcanic ash deposition and its associated, potentially far-reaching, impacts. Augustine volcano, conveniently located below the Polar Jet Stream, provides an ideal location to investigate the impact of Jet Stream stability on volcanic hazards. This chapter utilizes HYSPLIT volcanic ash modeling using parameters from the 1976 eruption of Augustine volcano applied to a series of hypothetical eruptions. Eruption conditions were modeled during extreme years with significant anomalies in internal climate modes to estimate the impact of an unstable Jet Stream on ash plume transportation over Alaska and the contiguous United States. Deposition outputs are then compared to current tephra maps to assess the influence of a changing climate on unexpected ash fall hazards. By improving our understanding of how climate change may affect atmospheric circulation, we can enhance our ability to forecast the trajectory, hazard, and distribution of erupted products within the atmosphere. Together, these chapters advance the understanding of magma dynamics at Augustine Volcano and provide a framework for assessing volcanic hazards in the context of environmental change. This work contributes to both the methodological toolkit for studying magmatic systems, the literature of documenting chemical changes in an important volcano, and the broader field of volcanic hazard mitigation in a changing climate.
Recommended Citation
Burkett, Emma Marie, "MAGMA ASSEMBLY AND ERUPTION DYNAMICS OF AUGUSTINE VOLCANO" (2025). Doctoral Dissertations. 2972.
https://scholars.unh.edu/dissertation/2972