Research geologist with expertise in 40Ar/39Ar and 238U-230Th geochronology. Research focuses on reconstructing the eruptive history of volcanic systems and understanding the magma plumbing systems that feed volcanic eruptions.
I have been conducting research on magmatic systems since 2008 with an emphasis on geochronology and geochemistry. The primary tool of my research is geochronology, particularly 40Ar/39Ar geochronology to determine the eruption age of volcanic rocks and 238U-230Th-226Ra geochronology to determine when the minerals hosted within volcanic rocks crystallized. By integrating geochronology with the chemical and isotopic composition of volcanic rocks and their minerals, I seek to understand (1) the eruptive history of volcanic systems, (2) how magma is generated and stored prior to volcanic eruptions, and (3) the rates and durations of volcanic eruptions.
I have worked on a variety of volcanic and plutonic systems over the course of my career. Prior to working with the U.S. Geological Survey, I conducted research on the Tuolumne Intrusive Suite in Yosemite National Park, California, South Sister volcano in Oregon, and the Yellowstone Plateau Volcanic Field in Wyoming. I began working at the U.S. Geological Survey in 2015 as a postdoc. My postdoctoral work focused on using 40Ar/39Ar geochronology to reconstruct the eruptive history of the Harrat Rahat volcanic field, Kingdom of Saudi Arabia, for the purposes of volcanic hazard assessment. Currently, I am using 40Ar/39Ar geochronology in combination with a variety of other geochemical data sets to understand the recent eruptive history at Yellowstone caldera in Wyoming, Newberry volcano in Oregon, Moffett and Adagdak volcanoes in Alaska, and the San Francisco Volcanic Field in Arizona.
In addition to studying volcanic systems, I also collaborate with researchers in the Geology, Minerals, Energy, and Geophysics Science Center to study the tectonic and geomorphic evolution of the western U.S.
Professional Experience
2018 - present: Research Geologist, USGS California Volcano Observatory
2015 - 2018: Research Geologist (postdoc), USGS California Volcano Observatory
2008 – 2014: Teaching and research assistant for the Department of Earth and Planetary Sciences, University of California - Davis
Education and Certifications
PhD, Geology: 2010 – 2014, University of California - Davis
Dissertation: Examining the origin and evolution of the magmatic system at Yellowstone caldera, WYMS, Geology: 2008 - 2010, University of California - Davis
Constraints on the nature of rhyolite genesis at South Sister volcano, Oregon through 238U-230Th zircon ages and 230Th-226Ra plagioclase agesBS, Geology: 2004 – 2008, University of North Carolina – Chapel Hill
Undergraduate thesis: Questioning the relationship between high-silica rhyolites and aplite dikes
Science and Products
Redefining the age of the lower Colorado River, southwestern United States: Reply
Crow et al. (2021) report new geochronologic and paleomagnetic data indicating that the lower Colorado River (CR) became integrated to the proto–Gulf of California (GOC) between 4.8 and 4.62 Ma instead of at ca. 5.3 Ma, as suggested by Dorsey et al. (2007, 2018). Dorsey et al. (2021) dispute this new chronology but offer no alternative explanation for one of the key data sets requiring it, new det
Redefining the age of the lower Colorado River, southwestern United States
Sanidine dating and magnetostratigraphy constrain the timing of integration of the lower Colorado River (southwestern United States and northern Mexico) with the evolving Gulf of California. The Colorado River arrived at Cottonwood Valley (Nevada and Arizona) after 5.24 Ma (during or after the Thvera subchron). The river reached the proto–Gulf of California once between 4.80 and 4.63 Ma (during th
Interpreting and reporting 40Ar/39Ar geochronologic data
The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ∼0.1%, thereby providing precise time constraints for a wide ra
Coexisting discrete bodies of rhyolite and punctuated volcanism characterize Yellowstone's post‐Lava Creek Tuff caldera evolution
Ion‐microprobe 206Pb/238U geochronology and trace element geochemistry of the unpolished rims and sectioned interiors of zircons from Yellowstone caldera's oldest post‐caldera lavas provide insight into the magmatic system during the prelude and aftermath of the caldera‐forming Lava Creek supereruption. The post‐caldera lavas compose the Upper Basin Member of the Plateau Rhyolite and fall into two
Constraining the early eruptive history of the Mono Craters rhyolites, California, based on 238U–230Th isochron dating of their explosive and effusive products
The Mono Craters are an overlapping chain of at least 28 domes and coulees located south of Mono Lake, east central California, and represent the most recent eruptions of high‐silica rhyolite magma in the Mono Lake‐Long Valley volcanic region. Regionally widespread tephra fall deposits from the Mono Craters serve as important chronostratigraphic markers for correlations of late Quaternary terrestr
Reconstructing lava flow emplacement histories with rheological and morphological analyses: the Harrat Rahat volcanic field, Kingdom of Saudi Arabia
Mafic volcanic fields are widespread, but few have erupted in historic times, providing limited observations of the magnitudes, dynamics, and timescales of lava flow emplacement in these settings. To expand our knowledge of effusive mafic eruptions, we must evaluate solidified flows to discern syn-eruptive conditions. The Harrat Rahat volcanic field in western Saudi Arabia offers a good opportunit
Timescales of magmatic differentiation from alkali basalt to trachyte within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia
A fundamental goal of igneous petrology is to quantify the duration of time required to produce evolved magmas following influx of basalt into the crust. However, in many cases, complex field relations and/or the presence of a long-lived magmatic system make it difficult to assess how basaltic inputs relate to more evolved magmas, therefore, precluding calculation of meaningful timescales. Here, w
Contrasting perspectives on the Lava Creek Tuff eruption, Yellowstone, from new U–Pb and 40Ar/39Ar age determinations
The youngest major caldera-forming event at Yellowstone was the ~ 630-ka eruption of the Lava Creek Tuff. The tuff as mapped consists of two major ignimbrite packages (members A and B), linked to widespread coeval fall deposits and formation of the Yellowstone Caldera. Subsequent activity included emplacement of numerous rhyolite flows and domes, and development of two structurally resurgent domes
Volcanic history of the northernmost part of the Harrat Rahat volcanic field, Saudi Arabia
We present a detailed geologic investigation of Pleistocene to Holocene mafic volcanism within the northernmost part of the Harrat Rahat volcanic field, proximal to the city of Al-Madinah, Saudi Arabia. Our study area covers ∼570 km2, and encompasses lava flows, scoria cones, and shield volcanoes of 32 mapped eruptive units consisting of continental, intraplate alkalic and tholeiitic basalts, hawa
A field trip guide to the petrology of Quaternary volcanism on the Yellowstone Plateau
The Yellowstone Plateau is one of the largest manifestations of silicic volcanism on Earth, and marks the youngest focus of magmatism associated with the Yellowstone Hot Spot. The earliest products of Yellowstone Hot Spot volcanism are from ~17 million years ago, but may be as old as ~32 Ma, and include contemporaneous eruption of voluminous mafic and silicic magmas, which are mostly located in th
The timing and origin of pre- and post-caldera volcanism associated with the Mesa Falls Tuff, Yellowstone Plateau volcanic field
We present new sanidine 40Ar/39Ar ages and paleomagnetic data for pre- and post-caldera rhyolites from the second volcanic cycle of the Yellowstone Plateau volcanic field, which culminated in the caldera-forming eruption of the Mesa Falls Tuff at ca. 1.3 Ma. These data allow for a detailed reconstruction of the eruptive history of the second volcanic cycle and provide new insights into the petroge
Mechanisms and timescales of generating eruptible rhyolitic magmas at Yellowstone caldera from zircon and sanidine geochronology and geochemistry
We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the (ca. 170 – 70 ka) Central Plateau Member eruptive episode – the most recent post-caldera magmatism at Yellowstone. We present 238U-230Th crystallization ages and trace-elem
Elemental and Strontium Isotopic Composition of Select Central Plateau and Upper Basin Member Rhyolites, Yellowstone Plateau Volcanic Field
The Yellowstone Plateau Volcanic field consists of lavas from the last two million years. The most recent volcanic units are the Central Plateau Member and the older Upper Basin Member rhyolites (Christiansen, 2001). Investigations into the elemental and isotopic composition of these lavas can provide insight into the recent volcanic history of the different eruptive episodes and provide constrain
Electron microprobe data for plagioclase, olivine, pyroxene, and spinel in volcanic rocks from the Matan volcanic center located within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia
Mineral compositions are reported for Quaternary volcanic rocks of the Matan volcanic center, northern Harrat Rahat, Saudi Arabia. Compositions were measured by wavelength-dispersive methods with the 5-spectrometer JEOL-8900 electron microprobe at the USGS facility in Menlo Park, California; background-corrected X-ray intensities were reduced to oxide weight concentrations with the JEOL proprietar
Ar isotope data for volcanic rocks from the northern Harrat Rahat volcanic field and surrounding area, Kingdom of Saudi Arabia
The data are the results of mass spectrometer experiments to measure 40Ar/39Ar ages of groundmass and mineral separates from volcanic rocks in northern Harrat Rahat, Kingdom of Saudi Arabia. The data were collected using a MAP216 noble gas mass spectrometer at the USGS facility in Menlo Park, Calif. These data were collected as part of a collaborative study conducted by the U.S. Geological Survey
Geologic map of the northern Harrat Rahat volcanic field, Kingdom of Saudi Arabia
Harrat Rahat, in the west-central part of the Kingdom of Saudi Arabia, is the largest of 15 Cenozoic harrats (Arabic for “volcanic field”) distributed on the Arabian plate. It extends more than 300 km north-south and 50 to 75 km east-west, and it covers an area of approximately 20,000 km2, has a volume of approximately 2,000 km3, and encompasses more than 900 observable vents. Volcanism commenced
Science and Products
- Publications
Redefining the age of the lower Colorado River, southwestern United States: Reply
Crow et al. (2021) report new geochronologic and paleomagnetic data indicating that the lower Colorado River (CR) became integrated to the proto–Gulf of California (GOC) between 4.8 and 4.62 Ma instead of at ca. 5.3 Ma, as suggested by Dorsey et al. (2007, 2018). Dorsey et al. (2021) dispute this new chronology but offer no alternative explanation for one of the key data sets requiring it, new detRedefining the age of the lower Colorado River, southwestern United States
Sanidine dating and magnetostratigraphy constrain the timing of integration of the lower Colorado River (southwestern United States and northern Mexico) with the evolving Gulf of California. The Colorado River arrived at Cottonwood Valley (Nevada and Arizona) after 5.24 Ma (during or after the Thvera subchron). The river reached the proto–Gulf of California once between 4.80 and 4.63 Ma (during thInterpreting and reporting 40Ar/39Ar geochronologic data
The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ∼0.1%, thereby providing precise time constraints for a wide raCoexisting discrete bodies of rhyolite and punctuated volcanism characterize Yellowstone's post‐Lava Creek Tuff caldera evolution
Ion‐microprobe 206Pb/238U geochronology and trace element geochemistry of the unpolished rims and sectioned interiors of zircons from Yellowstone caldera's oldest post‐caldera lavas provide insight into the magmatic system during the prelude and aftermath of the caldera‐forming Lava Creek supereruption. The post‐caldera lavas compose the Upper Basin Member of the Plateau Rhyolite and fall into twoConstraining the early eruptive history of the Mono Craters rhyolites, California, based on 238U–230Th isochron dating of their explosive and effusive products
The Mono Craters are an overlapping chain of at least 28 domes and coulees located south of Mono Lake, east central California, and represent the most recent eruptions of high‐silica rhyolite magma in the Mono Lake‐Long Valley volcanic region. Regionally widespread tephra fall deposits from the Mono Craters serve as important chronostratigraphic markers for correlations of late Quaternary terrestrReconstructing lava flow emplacement histories with rheological and morphological analyses: the Harrat Rahat volcanic field, Kingdom of Saudi Arabia
Mafic volcanic fields are widespread, but few have erupted in historic times, providing limited observations of the magnitudes, dynamics, and timescales of lava flow emplacement in these settings. To expand our knowledge of effusive mafic eruptions, we must evaluate solidified flows to discern syn-eruptive conditions. The Harrat Rahat volcanic field in western Saudi Arabia offers a good opportunitTimescales of magmatic differentiation from alkali basalt to trachyte within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia
A fundamental goal of igneous petrology is to quantify the duration of time required to produce evolved magmas following influx of basalt into the crust. However, in many cases, complex field relations and/or the presence of a long-lived magmatic system make it difficult to assess how basaltic inputs relate to more evolved magmas, therefore, precluding calculation of meaningful timescales. Here, wContrasting perspectives on the Lava Creek Tuff eruption, Yellowstone, from new U–Pb and 40Ar/39Ar age determinations
The youngest major caldera-forming event at Yellowstone was the ~ 630-ka eruption of the Lava Creek Tuff. The tuff as mapped consists of two major ignimbrite packages (members A and B), linked to widespread coeval fall deposits and formation of the Yellowstone Caldera. Subsequent activity included emplacement of numerous rhyolite flows and domes, and development of two structurally resurgent domesVolcanic history of the northernmost part of the Harrat Rahat volcanic field, Saudi Arabia
We present a detailed geologic investigation of Pleistocene to Holocene mafic volcanism within the northernmost part of the Harrat Rahat volcanic field, proximal to the city of Al-Madinah, Saudi Arabia. Our study area covers ∼570 km2, and encompasses lava flows, scoria cones, and shield volcanoes of 32 mapped eruptive units consisting of continental, intraplate alkalic and tholeiitic basalts, hawaA field trip guide to the petrology of Quaternary volcanism on the Yellowstone Plateau
The Yellowstone Plateau is one of the largest manifestations of silicic volcanism on Earth, and marks the youngest focus of magmatism associated with the Yellowstone Hot Spot. The earliest products of Yellowstone Hot Spot volcanism are from ~17 million years ago, but may be as old as ~32 Ma, and include contemporaneous eruption of voluminous mafic and silicic magmas, which are mostly located in thThe timing and origin of pre- and post-caldera volcanism associated with the Mesa Falls Tuff, Yellowstone Plateau volcanic field
We present new sanidine 40Ar/39Ar ages and paleomagnetic data for pre- and post-caldera rhyolites from the second volcanic cycle of the Yellowstone Plateau volcanic field, which culminated in the caldera-forming eruption of the Mesa Falls Tuff at ca. 1.3 Ma. These data allow for a detailed reconstruction of the eruptive history of the second volcanic cycle and provide new insights into the petrogeMechanisms and timescales of generating eruptible rhyolitic magmas at Yellowstone caldera from zircon and sanidine geochronology and geochemistry
We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the (ca. 170 – 70 ka) Central Plateau Member eruptive episode – the most recent post-caldera magmatism at Yellowstone. We present 238U-230Th crystallization ages and trace-elem - Data
Elemental and Strontium Isotopic Composition of Select Central Plateau and Upper Basin Member Rhyolites, Yellowstone Plateau Volcanic Field
The Yellowstone Plateau Volcanic field consists of lavas from the last two million years. The most recent volcanic units are the Central Plateau Member and the older Upper Basin Member rhyolites (Christiansen, 2001). Investigations into the elemental and isotopic composition of these lavas can provide insight into the recent volcanic history of the different eruptive episodes and provide constrainElectron microprobe data for plagioclase, olivine, pyroxene, and spinel in volcanic rocks from the Matan volcanic center located within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia
Mineral compositions are reported for Quaternary volcanic rocks of the Matan volcanic center, northern Harrat Rahat, Saudi Arabia. Compositions were measured by wavelength-dispersive methods with the 5-spectrometer JEOL-8900 electron microprobe at the USGS facility in Menlo Park, California; background-corrected X-ray intensities were reduced to oxide weight concentrations with the JEOL proprietarAr isotope data for volcanic rocks from the northern Harrat Rahat volcanic field and surrounding area, Kingdom of Saudi Arabia
The data are the results of mass spectrometer experiments to measure 40Ar/39Ar ages of groundmass and mineral separates from volcanic rocks in northern Harrat Rahat, Kingdom of Saudi Arabia. The data were collected using a MAP216 noble gas mass spectrometer at the USGS facility in Menlo Park, Calif. These data were collected as part of a collaborative study conducted by the U.S. Geological Survey - Maps
Geologic map of the northern Harrat Rahat volcanic field, Kingdom of Saudi Arabia
Harrat Rahat, in the west-central part of the Kingdom of Saudi Arabia, is the largest of 15 Cenozoic harrats (Arabic for “volcanic field”) distributed on the Arabian plate. It extends more than 300 km north-south and 50 to 75 km east-west, and it covers an area of approximately 20,000 km2, has a volume of approximately 2,000 km3, and encompasses more than 900 observable vents. Volcanism commenced - Multimedia
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