Michelle Coombs, PhD
I work on a variety of topics including improving observatory responses during eruptions, understanding magmatic systems, and elucidating eruptive histories of volcanoes. I've performed geologic studies throughout the Aleutian-Alaskan subduction zone and in Hawaii.
Biography
Dr. Michelle Coombs is the Acting Center Director of the U.S. Geological Survey's Volcano Science Center, which is home to the five U.S. volcano observatories and the Volcano Disaster Assistance Program. Michelle received her B.A. in geology from Williams College, and her Ph.D. in geology from the University of Alaska Fairbanks. She conducts a wide range of geologic studies related to volcanoes. These including using stratigraphy and geologic mapping to determine long-term eruptive histories and hazards; petrologic studies into subvolcanic magmatic systems; and studies of recent eruptions and their deposits to understand eruption triggering and processes. She has participated in numerous eruption responses including at Redoubt and Augustine in Alaska and at Kilauea in 2018 and is interested in improving operational and scientific responses to eruptions.
POSITIONS
2020–present: detail as Acting Director of the Volcano Science Center
2016–2020: Scientist-in-Charge, Alaska Volcano Observatory, Volcano Science Center, U.S. Geological Survey, Anchorage, AK
2004–2016: Research Geologist, Alaska Volcano Observatory
2001–2004: Research Geologist, Volcano Hazards Team, U.S. Geological Survey, Menlo Park CA
EDUCATION
Williams College, BA Geology, 1994
University of Alaska Fairbanks, PhD Geology, 2001
PUBLICATIONS
Science and Products
Generation of calc-alkaline magmas during crystallization at high oxygen fugacity: An experimental and petrologic study of tephras from Buldir Volcano, western Aleutian Arc, Alaska, USA
Despite agreement that calc-alkaline volcanism occurs at subduction zones and is responsible for the genesis of continental landmasses, there is no consensus on the source of the Fe-depleted signature hallmark to calc-alkaline volcanism. In this study, we utilize mafic tephras collected from Buldir Volcano to address the genesis of strongly calc-...
Waters, Laura; Cottrell, Elizabeth; Coombs, Michelle L.; Kelley, Katherine A. The eruptive history, magmatic evolution, and influence of glacial ice at long-lived Akutan volcano, eastern Aleutian Islands, Alaska, USA
New 40Ar/39Ar and whole-rock geochemical data are used to develop a detailed eruptive chronology for Akutan volcano, Akutan Island, Alaska, USA, in the eastern Aleutian island arc. Akutan Island (166°W, 54.1°N) is the site of long-lived volcanism and the entire island comprises volcanic rocks as old as 3.3 Ma. Our current study is on the 225...
Coombs, Michelle L.; Brian Jicha
U.S. Geological Survey 2018 Kīlauea Volcano eruption response in Hawai'i—After-action review
The 2018 Kīlauea Volcano eruption lasted 107 days, and now ranks as the most destructive event at Kilauea since 1790, and as one of the most costly volcanic disasters in U.S. history. Multiple simultaneous hazard events unfolded, including sustained seismic activity leading to collapse at the summit of Halema'uma'u crater and severe damage to the...
Williams, Dee M.; Avery, Vic F.; Coombs, Michelle L.; Cox, Dale A.; Horwitz, Lief R.; McBride, Sara K.; McClymont, Ryan J.; Moran, Seth C. Phase equilibrium of a high-SiO2, andesite at fO2 = RRO: Implications for Augustine volcano and other high-fO2 arc andesites
Understanding the impact of magmatic plumbing systems on explosive volcanic activity is important for hazard management. This study describes phase equilibria experiments using a high-silica andesite (HSA; SiO2 = 62.5 wt%) from the 2006 eruption of Augustine Volcano, Alaska. Experiments were conducted under H2O saturated conditions, f02...
De Angelis, Sarah H.; Larsen, Jessica F.; Coombs, Michelle L.; Utley, James E. P.; Dunn, Andrew P. Petrology of the 2016–2017 eruption of Bogoslof Island
The 2016–2017 eruption of Bogoslof primarily produced crystal-rich amphibole basalts. The dominant juvenile tephra were highly microlitic with diktytaxitic vesicles, and amphiboles had large reaction rims. Both observations support a magma history of slow ascent and/or shallow stalling prior to eruption. Plagioclase-amphibole-clinopyroxene...
Loewen, Matthew W.; Pavel Izbekof; Justin Moshrefzadeh; Coombs, Michelle L.; Jessica Larsen; Graham, Nathan; Michelle Harbin; Waythomas, Christopher F.; Wallace, Kristi L. Overview, chronology, and impacts of the 2016–2017 eruption of Bogoslof volcano, Alaska
The 2016–2017 eruption of Bogoslof volcano, a back-arc shallow submarine volcano in Alaska’s Aleutian arc, began in December 2016 and included 70 explosive events and at least two episodes of subaerial dome building. Because the volcano had no local monitoring stations during the eruption, a combination of distant seismic stations, regional...
Coombs, Michelle L.; Wallace, Kristi L.; Cameron, Cheryl; Lyons, John J.; Wech, Aaron; Angeli, Kim M.; Cervelli, Peter The 2018 rift eruption and summit collapse of Kilauea Volcano
In 2018, Kīlauea Volcano experienced its largest lower East Rift Zone (LERZ) eruption and caldera collapse in at least 200 years. After collapse of the Pu'u 'Ō'ō vent on 30 April, magma propagated downrift. Eruptive fissures opened in the LERZ on 3 May, eventually extending ~6.8 km. A 4 May earthquake (M6.9) produced ~5 m of fault slip. Lava...
Neal, Christina A.; Brantley, Steven; Antolik, Loren; Babb, Janet; Burgess, Matthew K.; Cappos, Michael; Chang, Jefferson; Conway, Sarah; Desmither, Liliana; Dotray, Peter; Elias, Tamar; Fukunaga, Pauline; Fuke, Steven; Johanson, Ingrid; Kamibayashi, Kevan; Kauahikaua, James P.; Lee, R. Lopaka; Pekalib, S.; Miklius, Asta; Shiro, Brian; Swanson, Don; Nadeau, Patricia; Zoeller, Michael H.; Okubo, P.; Parcheta, Carolyn; Patrick, Matthew R.; Tollett, William; Trusdell, Frank A.; Younger, Edward F.; Montgomery-Brown, Emily; Anderson, Kyle R.; Poland, Michael P.; Ball, Jessica L.; Bard, Joseph A.; Coombs, Michelle L.; Dietterich, Hannah R.; Kern, Christoph; Thelen, Weston; Cervelli, Peter; Orr, Tim R.; Houghton, Bruce F.; Gansecki, Cheryl; Hazlett, Richard; Lundgren, Paul; Diefenbach, Angela K.; Lerner, Allan; Waite, Greg; Kelly, Peter J.; Clor, Laura E.; Werner, Cynthia; Burgess, Matthew; Mulliken, Katherine; Fisher, Gary Short-term forecasting and detection of explosions during the 2016–2017 eruption of Bogoslof volcano, Alaska
We describe a multidisciplinary approach to forecast, rapidly detect, and characterize explosive events during the 2016–2017 eruption of Bogoslof volcano, a back-arc shallow submarine volcano in Alaska’s Aleutian arc. The eruptive sequence began in December 2016 and included about 70 discrete explosive events. Because the volcano has no local...
Coombs, Michelle L.; Wech, Aaron; Haney, Matthew M.; Lyons, John J.; Schneider, David; Schwaiger, Hans; Wallace, Kristi L.; Fee, David; Freymueller, Jeffrey T.; Schaefer, Janet; Tepp, Gabrielle
Postglacial eruptive history and geochemistry of Semisopochnoi volcano, western Aleutian Islands, Alaska
Semisopochnoi Island, located in the Rat Islands group of the western Aleutian Islands and Aleutian volcanic arc, is a roughly circular island composed of scattered volcanic vents, the prominent caldera of Semisopochnoi volcano, and older, ancestral volcanic rocks. The oldest rocks on the island are gently radially dipping lavas that are the...
Coombs, Michelle L.; Larsen, Jessica F.; Neal, Christina A. Amphibole reaction rims as a record of pre-eruptive magmatic heating: An experimental approach
Magmatic minerals record the pre-eruptive timescales of magma ascent and mixing in crustal reservoirs and conduits. Investigations of the mineral records of magmatic processes are fundamental to our understanding of what controls eruption style, as ascent rates and magma mixing processes are well known to control and/or trigger potentially...
De Angelis, S. H.; Larsen, J.; Coombs, Michelle L.; Dunn, A.; Hayden, Leslie A.
Significance of a near-source tephra-stratigraphic sequence to the eruptive history of Hayes Volcano, south-central Alaska
Bluffs along the Hayes River valley, 31 km northeast and 40 km downstream from Hayes Volcano, reveal volcanic deposits that shed new light on its eruptive history. Three thick (>10 cm) and five thin (<10 cm) tephra-fall deposits are dacitic in whole rock composition and contain high proportions of amphibole to pyroxene and minor biotite and...
Wallace, Kristi L.; Coombs, Michelle L.; Hayden, Leslie A.; Waythomas, Christopher F. Cogenetic late Pleistocene rhyolite and cumulate diorites from Augustine Volcano revealed by SIMS 238U-230Th dating of zircon, and implications for silicic magma generation by extraction from mush
Augustine Volcano, a frequently active andesitic island stratocone, erupted a late Pleistocene rhyolite pumice fall that is temporally linked through zircon geochronology to cumulate dioritic blocks brought to the surface in Augustine's 2006 eruption. Zircon from the rhyolite yield a 238U-230Th age of ∼25 ka for their unpolished rims, and...
Coombs, Michelle L.; Vazquez, Jorge A.
Volcano Watch — Bogoslof Volcano, Alaska: ongoing eruption through the Bering Sea
Hawai‘i is not the only island in the United States with an ongoing eruption involving hot lava and cold water.
Monitoring Alaska’s Remote and Restless Bogoslof Volcano
Bogoslof volcano, located in the Aleutian Islands about 98 km (61 mi) northwest of Dutch Harbor/Unalaska, is in an active eruption sequence that began in mid-December 2016 and continues today.