My research incorporates physical volcanology, igneous petrology, geochemistry, radiogenic and stable isotopes. My work thus far is focused on: (I) investigating mantle melt sources and magmatism in anomalous convergent margins, (II) phreatomagmatism and maar volcanoes, and now (III) magma storage depths and volatile element behavior.
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Magma Storage Depths at Mauna Loa
Come back soon for updates on my PhD research in the VIBE Lab!
Investigating Nascent Slab Tear Magmatism of the Maclaren River Volcanic Field
Brueseke, M.E., Benowitz, J.A., Bearden, A.T., Mann, M.E., and Miggins, D.P. (2023). Subduction disruption, slab tears: ca. 1 Ma true collision of an ~30-km-thick oceanic plateau segment recorded by Yakutat slab nascent tear magmatism. Terra Nova, 35, 49-57, https://doi.org/10.1111/ter.12628.
Flat slab subduction is characterized by shallow subduction angles (<30°) and often results in the near cessation of arc magmatism. Yet significant arc magmatism can be generated along the edge and along tears of the flat subducting slab and the processes which influence magma generation, along with the distribution of volcanism at slab edge/tear environments are unclear.
The Maclaren River volcanic field (MRVF) in south central Alaska lies above the surficial projection of the shallowly subducting Yakutat slab tear and provides an ideal place to investigate mantle upwelling in a slab tear/edge environment by studying their eruptive products.
To better constrain magma generation and mantle upwelling processes along flat slab/edge environments, I collaborated with Dr. Matt Brueseke to develop a petrogenetic model for the MRVF using field mapping, thin section petrography, whole rock major and trace element geochemistry, and radiogenic (Sr-Nd-Pb) and stable (B-Mg) isotopes.
Final results from my M.S. work will be published soon!
Lateral migration of explosive hazards during maar eruptions constrained from crater shapes
Graettinger, A.H., and Bearden, A.T. (2021). Lateral migration of hazards during maar eruptions constrained from crater shapes. Journal of Applied Volcanology, 10, 3, 1-14, https://doi.org/10.1186/s13617-021-00103-w.
Maar volcanoes are the end-product of subsurface phreatomagmatic explosions that can move vertically and laterally during an eruption. Constraining the distances that maar-forming explosions move laterally, and the number of relocations common to these eruptions, is vital for informing hazard scenarios and numerical simulations.
In this study, we used 241 intact Quaternary maar crater shapes to establish global trends in size and spacing of explosion position relocations. I sorted maar craters into shape classes based on the presence of uniquely identifiable combinations of overlapping circular components in their geometry. We were able to recognize the minimum number of explosion locations responsible for observed crater shapes and measure the size and spacing of the explosion footprints, the circular area of the largest crater produced by a single explosion of a given energy, that produce the crater shape. Thus, even in the absence of abundant observations of maar-type eruptions, the typical range, size and spacing of explosion positions are derived from maar crater shapes. Additional evaluation of larger maars, consistent with stratigraphic studies, indicates that centers of explosive activity, and thus the origin of ballistic and density current hazards, can move as many as twenty times during a maar-forming eruption. These results provide the first quantitative constraints on the scale and frequency of lateral migration in maar eruptions and these values can directly contribute to hazard models and eruption event trees in advance of future maar-type eruptions.
MaarVLS2.0 (Maar Volcano Location and Shape) Expansion
Alison Graettinger; Alexander Bearden (2018), "Maar Volcano Location and Shape (MaarVLS) database v 2.0," https://theghub.org/resources/4365.
The MaarVLS: Maar Volcano Location and Shape (pronounced marvelous) database establishes universal traits of Quaternary maar craters including typical sizes, shapes, and occurrence of these craters in different volcanic field types. The original version released in 2018 had 240 features. Version 2.0 released in 2021 includes 430 Quaternary maars with intact crater rims and literature to support the identification.
During my undergraduate, I collaborated with Dr. Alison Graettinger to expand this database by ~90% (n = 190 new features) by finding maar craters within the literature, manually digitizing their crater outlines, size, and shape parameters, and extracting information on their tectonic setting, volcanic field characteristics, composition, elevation, and age. Additionally, I created a new secondary database with more eroded maars and tuff cones that documents their existance and explains their exclusion from the main database.
We also found that 65% of maars lacked published composition data and 62% of maars lacked published age data.
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