My eclectic and evolving USGS career began in 1977 when I was 39. I’m a field-intensive continental geologist interested in magmatism, geomorphology, tectonics, and deep-time (not real-time) geologic history. I’ve emphasized on-foot authentic geologic mapping of blank spots on the map, largely in wilderness or otherwise uninhabited areas.
My early work attracted AGU’s Bowen Award for chemical petrology (magmatic zonation of the Bishop Tuff and Novarupta 1912, isotope evolution of caldera cycles at Yellowstone, advancing the model of fundamentally basaltic transcrustal magmatism [JGR 1981]; and I was excused the wild-goose chase of Soret effects in magma chambers). IAVCEI later gave me the Thorarinsson Medal in Volcanology, recognizing numerous papers on the Katmai region, the Cascades, the Chilean Andes, my deep-crustal MASH model of arc magmatism, and the granitic Mush model of rhyolite melt extraction. GSA recently gave me (and Judy Fierstein) the 2019 Florence Bascom Geologic Mapping Award, which celebrated what I love doing best (geologic maps of Mount Adams, Mount Baker, Three Sisters, Katmai, Simcoe Mountains, Pantelleria, Quizapu–Descabezado, Mammoth Mountain, Laguna del Maule, and Long Valley caldera. Early-on, I set aside my loner tendency (imprudent in remote areas) and teamed up with Judy Fierstein, an intrepid and indefatigable field partner of 41 years. Honi soit qui mal y pense. We survived or dodged many and varied risks together. The renowned Argon Geochronology Lab at Menlo Park (directed by Brent Dalrymple, Marv Lanphere, and Andy Calvert) has been an essential support of much of our work. My career owes much to many USGS colleagues, most of all to Patrick Muffler, Bob Christiansen, Paul Bateman, and Charlie Bacon.
Professional Experience
1966-1970 Naturalist, National Park Service
1973-1975 Instructor, University of California at Berkeley
1977 Postdoc with Professor Ian Carmichael, Berkeley
1977-date Research Geologist, U.S. Geological Survey. Projects at Yellowstone; Katmai, Valley of Ten Thousand Smokes, Kaguyak caldera (AK); Pantelleria (Italy); Mammoth Mountain, Long Valley caldera, Bishop Tuff, Death Valley NP, Mojave National Preserve (CA); Mount Adams, Mount Baker, Three Sisters, Simcoe Mountains (Cascades); Descabezado-Azul-Quizapu, Tupungato, Laguna del Maule (Chile)
2006-date Senior Scientist (ST), Department of the Interior
Co-P.I. on Scientific Plan (1986) and Proposal for Research Drilling (1987) at Katmai.
International Development Bank USGS-Chile-Peru-Bolivia project on Volcanic-hosted Precious-metal Deposits in the Andes, 1990.
Co-P.I., NSF project, Chile: "Life History of an Arc Volcano,” M.A. Dungan, leader; 1991–1993.
Scientific Advisory Team, Long Valley Observatory, California Volcano Observatory, 2002–.
Education and Certifications
Harvard College, Cambridge, Massachusetts (B.A., 1961)
University of California, Berkeley (Ph.D., 1977)
Dissertation Advisors: Ian S.E. Carmichael (UC Berkeley), Charles M. Gilbert (UC Berkeley), Herbert R. Shaw (USGS)
Affiliations and Memberships*
Editorial Board, Bulletin of Volcanology, 1991-2001.
Associate Editor, JGR, 1984-86; special issue on Open Magmatic Systems.
Associate Editor, Andean Geology (formerly Revista Geológica de Chile, 1987-present
USGS Volcano Science Center, Publications review & approval designee, 1996-2013.
Geological Society of America, Fellow.
American Geophysical Union (AGU), Fellow.
AGU Fellows Selection Committee 2008–2012
International Association of Volcanology & Chemistry of Earth's Interior (IAVCEI)
IAVCEI Honors and Awards Committee 2012–2015
Honors and Awards
Detur Book Prize, Harvard College, 1958, Humanities; awarded annually since 1657.
Outstanding Soldier of the Cycle, 1959, U.S. Army.
Phi Beta Kappa, Harvard College, 1960 (Junior year election of top 8 in class of 1100).
Boston Marathon 1960, 29th place (Medals to top 35).
Sheldon Traveling Fellow, Harvard, 1961–1962 (Europe, Middle East, South Asia).
G.K. Gilbert Fellowship (U.S. Geological Survey), Chilean Andes, 1983–1985.
N.L. Bowen Award, 1985, American Geophysical Union.
Fellow of the Geological Society of America, 1985
Fellow of the American Geophysical Union, 1995.
Thorarinsson Medal, International Association of Volcanology & Chemistry of Earth's Interior: highest award in International Volcanology, 2004.
Meritorious Service Award, Department of the Interior, 2004.
Bascom Geologic Mapping Award, Geological Society of America, 2019
Abstracts and Presentations
Circum-Pacific Plutonism Project (IGCP), 1977; Invited Speaker, Japan-Korea Excursion.
Penrose Conference on Granitic Magmas, 1978; Invited Keynote Speaker.
Gordon Conference on Silicate Melt Structure, 1979; Invited Keynote Speaker.
Penrose Conference on Silicic Volcanism, 1980; Invited Keynote Speaker.
IAVCEI Conference on Arc Volcanism, Tokyo, 1981; Invited Speaker.
Tin Resources Working and Information Group; 1983.
USGS Distinguished Bradley Lecturer, 1983.
Co-Convenor of Conference on Open Magmatic Systems, Taos, New Mexico, 1984.
Workshops on Geothermal Resources of the Cascade Range, 1985; 1988; panelist, speaker.
IAVCEI Conference, New Zealand, 1986; Invited Speaker.
Hawaii Symposium on How Volcanoes Work, Hilo, 1987; Symposium Organizer.
IAVCEI—IUGG General Assembly, Vancouver, 1987; Symposium Organizer.
IAVCEI General Assembly, Santa Fe, 1989; Program Committee.
IAVCEI Commission on Explosive Volcanism: Valley of Ten Thousand Smokes (Alaska) field-trip leader; 10 days on foot, 1991.
GSA Annual Meeting, Seattle, 1994, Opening Keynote Speaker on Cascade Magmatism.
Penrose Conference on Silicic Magmatism, Mammoth Lakes, CA, 2001; Opening Keynote Speaker, “Critical overview of silicic magmatism.”
Scientific Committee, IAVCEI General Assembly (Chile, 2004), 2002-04. Convener of Symposium on Arc Magmatism. Thorarinsson Lecturer.
GSA Cordilleran Section Meeting, 2010, Field trip leader, Long Valley and Mammoth Mountain.
Devils Postpile National Monument, Centennial Celebration, 2011, Field trip leader.
National Park Service Centennial Speaker 2016, at Devils Postpile National Monument.
IAVCEI General Assembly, Portland, OR, 2017, Invited Keynote Speaker on Geologic Mapping. Field-trip leader to Long Valley caldera and the Bishop Tuff.
Science and Products
Database for the Geologic Map of Three Sisters Volcanic Cluster, Cascade Range, Oregon
Geologic map of the Simcoe Mountains Volcanic Field, main central segment, Yakama Nation, Washington
Geologic map of Three Sisters volcanic cluster, Cascade Range, Oregon
Geologic map of the Mount Baker 30- by 60-minute quadrangle, Washington
Geologic Map of the Katmai Volcanic Cluster, Katmai National Park, Alaska
Geologic map of the Mount Adams volcanic field, Cascade Range of southern Washington
Ages of the granitic basement of Long Valley Caldera, California, USA, and siting of the Quaternary granite-rhyolite pluton
Precaldera mafic magmatism at Long Valley, California: Magma-tectonic siting and incubation of the Great Rhyolite System
Trachyandesite of Kennedy Table, its vent complex, and post−9.3 Ma uplift of the central Sierra Nevada
Comparative rhyolite systems: Inferences from vent patterns and eruptive episodicities: Eastern California and Laguna del Maule
No ring fracture in Mono Basin, California
Frequency of volcanic eruptions in the Mammoth Lakes Sierra
Monogenetic origin of Ubehebe Crater maar volcano, Death Valley, California: Paleomagnetic and stratigraphic evidence
Geologic field-trip guide to Long Valley Caldera, California
Graphite in the Bishop Tuff and its effect on postcaldera oxygen fugacity
Long Valley Caldera Lake and reincision of Owens River Gorge
The timing of compositionally-zoned magma reservoirs and mafic 'priming' weeks before the 1912 Novarupta-Katmai rhyolite eruption
Eruptive history of Mammoth Mountain and its mafic periphery, California
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
- Data
Database for the Geologic Map of Three Sisters Volcanic Cluster, Cascade Range, Oregon
A database of geologic map of Three Sisters Volcanic Cluster as described in the original abstract: The geologic map represents part of a late Quaternary volcanic field within which scores of eruptions have taken place over the last 50,000 years, some as recently as ~1,500 years ago. No rocks of early Pleistocene (or greater) age crop out within the map area, although volcanic and derivative sedi - Maps
Geologic map of the Simcoe Mountains Volcanic Field, main central segment, Yakama Nation, Washington
Mountainous parts of the Yakama Nation lands in south-central Washington are mostly covered by basaltic lava flows and cinder cones that make up the Simcoe Mountains volcanic field. The accompanying geologic map of the central part of the volcanic field has been produced by the U.S. Geological Survey (USGS) on behalf of the Water Resources Program of the Yakama Nation. The volcanic terrain stretchGeologic map of Three Sisters volcanic cluster, Cascade Range, Oregon
The cluster of glaciated stratovolcanoes called the Three Sisters—South Sister, Middle Sister, and North Sister—forms a spectacular 20-km-long reach along the crest of the Cascade Range in Oregon. The three eponymous stratocones, though contiguous and conventionally lumped sororally, could hardly display less family resemblance. North Sister (10,085 ft), a monotonously mafic edifice at least as olGeologic map of the Mount Baker 30- by 60-minute quadrangle, Washington
No abstract available.Geologic Map of the Katmai Volcanic Cluster, Katmai National Park, Alaska
This digital publication contains all the geologic map information used to publish U.S. Geological Survey Geologic Investigations Map Series I-2778 (Hildreth and Fierstein, 2003). This is a geologic map of the Katmai volcanic cluster on the Alaska Peninsula (including Mount Katmai, Trident Volcano, Mount Mageik, Mount Martin, Mount Griggs, Snowy Mountain, Alagogshak volcano, and Novarupta volcano)Geologic map of the Mount Adams volcanic field, Cascade Range of southern Washington
One of the dominating peaks of the Pacific Northwest, Mount Adams, stands astride the Cascade crest, towering 3 km above the surrounding valleys. The icecapped 3742-m (12,276') stratovolcano has for centuries been called Pah-to by the region's indigenous people, who hold the mountain sacred as a symbol of continuity and a source of prosperity and inspiration. Comparable reverence helped secure inc - Multimedia
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Filter Total Items: 65
Ages of the granitic basement of Long Valley Caldera, California, USA, and siting of the Quaternary granite-rhyolite pluton
The leucogranitic crystal-mush pluton beneath the iconic Long Valley Caldera, California, USA, released >820 km3 of crystal-poor Pleistocene rhyolite, which was hosted by numerous Mesozoic granitic plutons, only a few of which had been dated until now. Reported here are U-Pb zircon ages, determined by sensitive high-resolution ion microprobe−reverse geometry (SHRIMP-RG), for 11 circumcaldera graniAuthorsEdward Hildreth, Judith E. Fierstein, Jorge A. VazquezPrecaldera mafic magmatism at Long Valley, California: Magma-tectonic siting and incubation of the Great Rhyolite System
The iconic volcanic center at Long Valley has released ∼820 km3 of rhyolite in at least 110 eruptions. From 2.2 Ma until 0.23 Ma, products were exclusively rhyolitic, and ∼ 700 km3 were high-silica rhyolite severely depleted in Sr, Ba, and Eu. The rhyolitic interval was preceded by an interval from 3.9 to 2.6 Ma with numerous basalt-andesite-dacite eruptions accompanied by no rhyolite at all. We hAuthorsEdward Hildreth, Judith E. Fierstein, Andrew T. CalvertTrachyandesite of Kennedy Table, its vent complex, and post−9.3 Ma uplift of the central Sierra Nevada
Tectonic interpretation of the central Sierra Nevada—whether the crest of the Sierra Nevada (California, USA) was uplifted in the late Cenozoic or whether the range has undergone continuous down-wearing since the Late Cretaceous—is controversial, since there is no obvious tectonic explanation for renewed uplift. The strongest direct evidence for late Cenozoic uplift of the central Sierra Nevada coAuthorsEdward Hildreth, Judith Fierstein, Fred M. Phillips, Andrew T. CalvertComparative rhyolite systems: Inferences from vent patterns and eruptive episodicities: Eastern California and Laguna del Maule
Distilling my experience in having field mapped in detail the volcanic fields at Laguna del Maule and Long Valley and having worked out their time-volume-composition magmatic histories, I compare and contrast the postglacial rhyolites of the former with six multi-vent eruptive sequences of rhyolite in California. Compilations and discussions are made of volcanic-field areas and longevities, theirAuthorsEdward HildrethNo ring fracture in Mono Basin, California
In Mono Basin, California, USA, a near-circular ring fracture 12 km in diameter was proposed by R.W. Kistler in 1966 to have originated as the protoclastic margin of the Cretaceous Aeolian Buttes pluton, to have been reactivated in the middle Pleistocene, and to have influenced the arcuate trend of the chain of 30 young (62−0.7 ka) rhyolite domes called the Mono Craters. In view of the frequency aAuthorsEdward Hildreth, Judith Fierstein, Juliet Ryan-DavisFrequency of volcanic eruptions in the Mammoth Lakes Sierra
Geologists recognize lavas and ash deposits from about 60 past eruptions in the area around Mammoth Mountain and Devils Postpile, California. This raises the unanswerable question, “When will it erupt again?” An alternative, answerable, and informative question is, “How often has it erupted?”In the Mammoth Lakes Sierra, geologists have mapped in great detail all the lavas and ash deposits producedAuthorsWes Hildreth, Andrew T. Calvert, Judith Fierstein, Mae MarcaidaMonogenetic origin of Ubehebe Crater maar volcano, Death Valley, California: Paleomagnetic and stratigraphic evidence
Paleomagnetic data for samples collected from outcrops of basaltic spatter at the Ubehebe Crater cluster, Death Valley National Park, California, record a single direction of remanent magnetization indicating that these materials were emplaced during a short duration, monogenetic eruption sequence ~ 2100 years ago. This conclusion is supported by geochemical data encompassing a narrow range of oxiAuthorsDuane E. Champion, Andrew J. Cyr, Judith Fierstein, Edward HildrethGeologic field-trip guide to Long Valley Caldera, California
This guide to the geology of Long Valley Caldera is presented in four parts: (1) An overview of the volcanic geology; (2) a chronological summary of the principal geologic events; (3) a road log with directions and descriptions for 38 field-trip stops; and (4) a summary of the geophysical unrest since 1978 and discussion of its causes. The sequence of stops is arranged as a four-day excursion forAuthorsWes Hildreth, Judy FiersteinGraphite in the Bishop Tuff and its effect on postcaldera oxygen fugacity
Several cubic kilometers of Paleozoic graphite-bearing argillitic country rocks are present as lithic fragments in Bishop Tuff ignimbrite and fallout. The lithics were entrained by the 650 km3 of rhyolite magma that vented during the 5- to 6-day-long, caldera-forming eruption at Long Valley, California. The caldera is floored by a 350 km2 roof plate that collapsed during the eruption and consistsAuthorsEdward Hildreth, Juliet Ryan-Davis, Benjamin HarlowLong Valley Caldera Lake and reincision of Owens River Gorge
Owens River Gorge, today rimmed exclusively in 767-ka Bishop Tuff, was first cut during the Neogene through a ridge of Triassic granodiorite to a depth as great as its present-day floor and was then filled to its rim by a small basaltic shield at 3.3 Ma. The gorge-filling basalt, 200 m thick, blocked a 5-km-long reach of the upper gorge, diverting the Owens River southward around the shield into RAuthorsWes Hildreth, Judy FiersteinThe timing of compositionally-zoned magma reservoirs and mafic 'priming' weeks before the 1912 Novarupta-Katmai rhyolite eruption
The June 6, 1912 eruption of more than 13 km3 of dense rock equivalent (DRE) magma at Novarupta vent, Alaska was the largest of the 20th century. It ejected >7 km3 of rhyolite, ~1.3 km3 of andesite and ~4.6 km3 of dacite. Early ideas about the origin of pyroclastic flows and magmatic differentiation (e.g., compositional zonation of reservoirs) were shaped by this eruption. Despite being well studiAuthorsBrad S. Singer, Fidel Costa, Jason S. Herrin, Wes Hildreth, Judith FiersteinEruptive history of Mammoth Mountain and its mafic periphery, California
This report and accompanying geologic map portray the eruptive history of Mammoth Mountain and a surrounding array of contemporaneous volcanic units that erupted in its near periphery. The moderately alkaline Mammoth eruptive suite, basaltic to rhyodacitic, represents a discrete new magmatic system, less than 250,000 years old, that followed decline of the subalkaline rhyolitic system active beneaAuthorsWes Hildreth, Judy FiersteinNon-USGS Publications**
Hildreth, W., 1976, Death Valley Geology: Death Valley Natural History Association, Furnace Creek, CA, 64 p.
Ewart, A., Hildreth, W., and Carmichael, I.S. E., 1975, Quaternary acid magma in New Zealand: Contributions to Mineralogy and Petrology, v. 51, p. 1–27.
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
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*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government