Volcanic deformation as an indicator of mechanical stability and eruption susceptibility

Cabaniss, Haley E

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Description

Title

Volcanic deformation as an indicator of mechanical stability and eruption susceptibility

Author(s)

Cabaniss, Haley E

Issue Date

2020-04-30

Director of Research (if dissertation) or Advisor (if thesis)

Gregg, Patricia M

Doctoral Committee Chair(s)

Gregg, Patricia M

Committee Member(s)

• Nooner, Scott L
• Marshak, Stephen
• Johnson, Thomas
• Stewart, Michael

Department of Study

Geology

Discipline

Geology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Volcanology
• Numerical Modeling
• Deformation Modeling
• Seismicity
• Stress
• Mechanics
• Marine Geophysics
• Axial Seamount
• Taupo Caldera
• Eruption Triggers

Abstract

Caldera-forming eruptions are amongst the greatest natural hazards on our planet, erupting hundreds of cubic kilometers of material with severe local and global impacts that pose great risks to human health and society at large. Understanding how these systems form and what triggers their catastrophic eruption therefore is critical for assessing future hazards. The classic paradigm in volcanology is that eruption occurs when the pressure within a magma reservoir exceeds the confining strength of the host rock surrounding it. However, this paradigm has been widely debated in recent years as quantitative constraints on critical “overpressure” to trigger eruption remain uncertain. Recent models of volcano unrest suggest that eruptions are triggered when conditions of critical stress are achieved in the host rock around a magma reservoir, and in absence of an overpressure-driven mechanism, external factors such as faulting and tectonic forcing have been suggested as potential catalysts. Through a series of three-dimensional thermo-mechanical numerical experiments, this dissertation bridges competing paradigms in volcanology of internal and external eruption triggers by identifying greater complexity in and coupling of the processes responsible for triggering caldera eruptions. To account for the diversity observed in caldera systems, this work examines the supereruptions of the Taupo Caldera in New Zealand, and recent eruptions of the submarine volcano, Axial Seamount. I address the effect of tectonic stresses on triggering the eruption of the Taupo Caldera, and reveal that mechanical stability of shallow, silicic magmatic systems are intrinsically linked to tectonic setting. For the first time from a mechanical perspective, this work illustrates that large silicic melt bodies are likely reactivated from cold, crystalline “mush” storage on short timescales of decades to thousands of years (in agreement with recent geochemical investigations). In another series of numerical experiments, I identify the submarine volcano, Axial Seamount, as a system which has experienced both internal and external controls on eruption. In particular, models indicate that microseismicity (induced by the expansion of the Axial magma reservoir) serves as both an eruption precursor and an eruption buffer, reducing crustal stress and delaying model predictions of eruption. Despite stress release via seismicity, model-predicted eruptions occur as a critical threshold of reservoir pressure is exceeded, indicating critical overpressurization as the mechanism of eruption at Axial Seamount. The findings reported in this dissertation suggest significant variability in volcanic eruption triggers and illustrate the importance evaluating eruption triggers as they relate to the complete volcanic system.

Graduation Semester

2020-05

Type of Resource

Thesis

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Copyright 2020 Haley Cabaniss

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