Dissertations, Theses, and Capstone Projects

Date of Degree

6-2023

Document Type

Dissertation

Degree Name

Ph.D.

Program

Earth & Environmental Sciences

Advisor

Marc-Antoine Longpré

Committee Members

Benjamin Black

Kennet Flores

Terry Plank

Subject Categories

Geochemistry | Geology | Volcanology

Keywords

mineralogy, petrology, diffusion chronometry, thermodynamic models

Abstract

Across all scales of human relationships (i.e. person-to-person, country-to-country, etc.), qualms can take the form of long-standing wars, quick and intense bouts, or petty exchanges. While our understanding of human behavior is ever increasing, reactions and behaviors of self and others may still come as a surprise. Expressions of disagreement can occur suddenly or following years to centuries of accumulated grievances. The solid earth is also a system that behaves (like human emotion) predictably at times and unpredictably at other times. Some volcanoes, a tangible surface expression of solid earth processes, exhibit precursory signals prior to eruption (e.g. the bulging of the Mt. St. Helens, edifice, USA), while others erupt violently without warning or time-sensitive signals (e.g. the phreatomagmatic eruptions at Mt. Ontake, Japan and Whakaari/White Island, New Zealand). Interpersonal human systems (at any scale) are complex beyond our current comprehension; yet, we work towards understanding each other and ourselves to minimize the negative impacts that come in association with fights, wars, and passive-aggressive spats. Likewise, to minimize the negative impacts of volcanic systems, it is not necessary to understand how every bit of the system works – just the time-sensitive dynamic behaviors that would directly jeopardize human life. In this work, we aim to untangle the ‘accumulation of grievances’ (magma supply) at two volcanoes (Momotombo Volcano, Nicaragua and Cumbre Vieja, La Palma, Canary Islands, Spain) to gain a better understanding of the timings of magma supply to a volcano-magmatic system by recharge and how that influences eruption onset and duration. In addition to magma recharge, eruption-influencing perturbations simultaneously occurring within a volcanic-magmatic system include magma mixing, assimilation of wall rock, volatile fluxing, magma differentiation, and the interplay of crystallization and volatile exsolution (Blake, 1984; Caricchi et al., 2018; Cassidy et al., 2018; Malfait et al., 2014; Tait et al., 1989; Tramontano et al., 2017; Blundy, 2022). It has been established that the thermal structure and thermodynamic constraints (mineral assemblage, volatile content, fO2, etc.) that govern the lower ‘hot’ parts of magma reservoirs modulate ascending liquid chemistry and the timings of magma evolution (Annen et al., 2006; Weber et al., 2020; Blundy, 2022). In this study, we consider igneous processes that take place between lower parts of a magma reservoir (lower crust to mantle) and the surface of the earth. The timings and nature of these petrology-modulated processes are critical to understand because of the direct link to mechanical properties like viscosity; which, in combination with dynamic processes, like ascent rate and outgassing efficiency, strongly influence the styles (explosive-effusive) and timings of eruptions (Cassidy et al., 2018 and references therein; La Spina et al., 2021). Thus, to improve our understanding of when, how, and for how long volcanoes erupt, it is pertinent that we work towards linking magmatic system parameters (e.g. volume, viscosity, etc.) with the timing and nature of dynamic surficial expressions (e.g. tremor, surface degassing, etc.). In chapter one of this work, we investigate the role of magma recharge and volatile exsolution in mobilizing an arc-based crystal-rich system in repose for 110 years. To do this, we examine the textures and chemistries of erupted products – crystals, melt inclusions in crystals, glasses, and whole rocks sourced from tephra and lava samples from the most recent (2015-2016) eruption at Momotombo volcano, Nicaragua. We then apply a series of chemical equilibria calculations and thermodynamic models to constrain the conditions of the system leading up to eruption. In chapter two of this work, we examine the timings of magma recharge across seven historic eruptions with varying repose periods at Cumbre Vieja, La Palma, Canary Islands. To do this, we calculate diffusion timescales (time between recharge and eruption) across diffusion-dominated chemical zones in olivine crystals from all seven eruptions. Then, we apply thermodynamic models to growth-dominated chemical zones in olivine to constrain ascent conditions. In chapter three of this work, we investigate how magma supply varies over the duration of eruption through chemical analyses of daily-collected tephra glasses from the 2021 eruption at Tajogaite, Cumbre Vieja, La Palma, Canary Islands, Spain. We then compare our time series recording melt chemistry changes to time series of surface signals (tremor, plume height, gas emissions) to decipher the relationship between melt chemistry and eruption dynamics.

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