Eruption Initiation Mechanisms and Timescales at a Very-High-Threat Washington Volcano: Clues from Crystal Cargo in Lavas from Mount Baker (Koma Kulshan)

Author

Emily YoderFollow

Document Type

Thesis

Date of Degree Completion

Spring 2024

Degree Name

Master of Science (MS)

Department

Geological Sciences

Committee Chair

Dr. Hannah Shamloo

Second Committee Member

Dr. Chris Mattinson

Third Committee Member

Dr. Susan DeBari

Fourth Committee Member

Dr. Kristina Walowski

Abstract

Understanding the timescales of pre-eruptive processes is key for improving forecast models of future eruptions. Mount Baker (Koma Kulshan), WA, is part of the northern Cascade volcanic arc and classified as a very high threat volcano. However, we lack an understanding of the duration of time between the final magmatic process before eruption (potentially the process that initiated the eruption) and the eruption itself. This study focuses on (1) estimating eruption initiation timescales via diffusion chronometry and (2) determining eruption initiation mechanisms for three andesitic lava flows from Mount Baker: Dobbs Creek (~119 ka), Dobbs Cleaver (~105 ka), and Swift Creek (~48 ka). The crystal cargo of each lava comprise multiple co-crystallizing assemblages, characterized in prior work using textures and geochemistry of individual phenocrysts and crystal clusters. Specifically, this study examines plagioclase and clinopyroxene crystals that occur as individual phenocrysts and/or within crystal clusters representing each assemblage. Both plagioclase and clinopyroxene crystals have thin (~10 to 20 μm) reversely zoned rims in equilibrium with a basaltic to basaltic-andesite magmatic component, or normally zoned rims in equilibrium with a dacitic magmatic component. Common iv disequilibrium textures (i.e., reverse zoning, resorption) suggest multiple magma mixing events before eruption. Major and trace element chemical transects across interior to rim zone boundaries were collected via EPMA and LA-ICP-MS for diffusion chronometry modeling. Temperature of diffusion was estimated based on the mineral rim composition and paired equilibrium liquid with plagioclase-liquid and clinopyroxene-liquid thermometers. Both chemical and textural evidence support mafic recharge and heating as eruption initiation mechanisms for these three Mount Baker lavas. Most significantly, eruption initiation timescales from Sr and Mg diffusion in plagioclase as well as Mg-Fe interdiffusion in clinopyroxene are very short, typically on the order of weeks to months, and are similar across the Dobbs Creek, Dobbs Cleaver, and Swift Creek lavas. In addition, they are similar to initiation timescales constrained for other Cascade volcanoes, indicating a need to be prepared for short response times across the Cascades in the scenario of future volcanic unrest.

Recommended Citation

Yoder, Emily, "Eruption Initiation Mechanisms and Timescales at a Very-High-Threat Washington Volcano: Clues from Crystal Cargo in Lavas from Mount Baker (Koma Kulshan)" (2024). All Master's Theses. 1943.
https://digitalcommons.cwu.edu/etd/1943