Holli Frey

Holli, at the summit of South Sister, Oregon.

This has been a busy year, with more than a dozen presentations at AGU in New Orleans in December from our Dominica Keck project, a few manuscripts published, and the start of a new research project in the cen-tral Oregon Cascades. The most exciting development is that our work on the young zircons in Dominica was published in the October 2018 issue of Geology. Our Geology paper used zircon U-Th age data collect-ed by Sarah Brehm ’15 and Rebecca Babiak ’16 (both co-authors) and population distribution modelling done by my colleague Matt Manon to define periods of enhanced crystallization in the Roseau Valley in Dominica. This has implications for magma storage conditions and suggests that magma bodies are cold for most of their lifetime and experience very brief periods of thermal rejuvenation prior to eruption. If this is
the case, geophysical tools can be used to detect the presence of melt and potentially be another way to monitor for volcanic unrest. Magma storage conditions is one of the biggest issues in igneous petrology right now and I’ll be giving a talk on the subject at GSA in Indianapolis. One of our other Dominica projects is also about to published, in the Journal of Volcanology and Geothermal Research – chemical and isotopic time-series of hydrothermal waters in Dominica from 2013-2017. Co-authors on this manuscript include students Tara Metzger ’15, Kathryn DeFranco ’16, and Carli Aragosa ‘17.
In 2017-18, we had another great set of student Dominica theses through our Keck project, including the work of Abadie Ludlam ’18 and Sarah Hickernell ’18. Abadie looked at hornblende crystals from several different lava domes and was able to deduce heating versus decompression histories based on elemental mapping on the SEM. Sarah studied multiple populations of enclaves in the Micotrin lava dome to characterize magma mingling and eruption triggers. Both students presented at AGU, NE GSA, and had successful honors defenses of their theses. In addition, Sarah earned the Union College Sigma Xi award, given to the best science presentation at our yearly Steinmetz Research Symposium. Given the logistical challenges in the difficult aftermath of Hurricane Maria, I did not do fieldwork with students in Dominica this summer. I am beginning a new project in the South Sister volcanic field with my col-league, Dr. Laura Waters (Sonoma State).
Holli Frey
My first project is to characterize the eruption history of the young rhyolitic deposits through U-Th dating of the zircons. Two students accompanied me to Oregon, Rebecca Lippitt ’19 and Madi Corcoran ’19, spending a week camping at the base of South Sister and doing lots of long hikes to collect samples. The highlight was a trip to Crater Lake – the amazing remnants of a caldera forming explosive eruptions ~7 ka. Rebecca is characterizing through bulk and mineral chemistry some of the ill-defined tuffs around the Tumalo-Bend area of Oregon. Madi is looking at the plagioclase textures and compositions in the rhyolites on the periphery of South Sister volcano. Both students have been busy collecting data from the ICP-MS and becoming adept at using the SEM.

Holli, Matt, Natalie (7), and Zoe (5) on top of Mt. Joe on our Adirondack vacation in August. The aspiring geologists also climbed Catamount and their first 46er peak, Mount Phelps.

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