As Scientist-in-Charge of the California Volcano Observatory (CalVO), I lead the ~35 geologists, geophysicists and hydrologists that study and monitor volcanoes in California and other domestic and international volcanoes. CalVO also maintains laboratories to study many aspects of volcanic behavior. CalVO is located in Menlo Park and Moffett Field on the San Francisco Peninsula.
Research Accomplishments
Eruptive history of Cascade and Aleutian Arc Volcanoes, an example from the Three Sisters
Most mapped volcanoes appear to be built episodically and characterizing these episodes offers insight into future eruptive behavior. Middle Sister is the most chemically diverse and youngest of the Three Sisters Volcanic Cluster (Hildreth et al., 2012). Dated, mapped lava flows precede and postdate the remarkably productive (fourfold increase in output between 50 – 15 thousand years) and silicic rhyolite episode best exposed at South Sister. Our Middle Sister paper (Calvert et al., 2018) chronicles mafic, intermediate and silicic eruptions from peripheral and central vents and compares timing and compositions with the largely-silicic products of South Sister (Fierstein et al., 2011).
Growth of Hawaiian volcanoes
Despite being some of the best-studied volcanoes on earth, little was known about the inception ages and lifespans of Hawaiian volcanoes, largely because early-erupted samples are inaccessible and all samples are difficult to date accurately and precisely. The chemical progression from alkalic to tholeiitic and back to alkalic compositions is well-characterized, yet the timescales of this variation have been difficult to constrain. Even volume estimates vary significantly because a new edifice may develop on the flank of an older shield. A collaborative agreement between USGS and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) provided submersible access to early-erupted materials and a unique opportunity to constrain inception ages and compositional evolution rates of the most productive volcanic center on earth.
We undertook to date submarine samples from the south flank of Kilauea, Mahukona and Hilo Ridge to develop a basic framework for the time-volume development of Hawaiian volcanoes. Lavas from an intact section of weakly alkalic basalts on submarine flank of Kilauea and strongly alkalic blocks from debris flows beneath Kilauea are indistinguishable at 147±14 ka and older strongly alkalic samples range from 212±38 ka to 280±20 ka (Calvert and Lanphere, 2006). This finding shows that Kilauea is a relatively young volcano and the voluminous younger, tholeiitic lavas were erupted at higher rates than generally assumed. This work refutes previous studies dating the tholeiitic lavas at 500 ka along the active rift zone and in drill core. Weakly-alkalic rocks from Hilo Ridge yielded 1150±20 ka ages, far too old to belong to their assumed source, Mauna Kea. Hilo Ridge instead belongs to Kohala volcano, which is now estimated to have erupted from 1,200 to 280 ka (Lipman and Calvert, 2011). Mauna Kea had been reported to be more voluminous than other centers on Hawaii, however, this result requires that the submarine Hilo Ridge belongs to Kohala, not Mauna Kea, reducing the estimated eruptive volume of Mauna Kea by nearly 50% (42 to 22 km3) a
Education and Certifications
Ph.D., University of California – Santa Barbara
Dissertation: Metamorphism and exhumation
M.S./B.S., Stanford University (both degrees conferred June 1992)
Thesis: Structural Evolution and Thermochronology of the Kigluaik Mountains, Seward Peninsula, Alaska
Science and Products
Dataset Establishing Temporal Duration of Two Shield Volcanoes in Northern California
This dataset contains paleomagnetic data from 30 sites at two locations in northern California (16 sites at Ash Creek Butte and 14 sites at Crater Mountain), magnetic susceptibility-temperature curves for selected samples at Ash Creek Butte, and geochemical data for map units at Crater Mountain.
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
Geologic 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 ol
Filter Total Items: 39
Paleomagnetically defined brief lifespans for two large shield volcanoes in the Cascades Arc
Mafic to intermediate shield volcanoes with multi-cubic-kilometer eruptive volumes are common in the Cascades Volcanic Arc, but little is known about their eruptive histories as either singular or sustained episodes, or the total time required for their construction. Paleomagnetic data were collected from the lava flows of Ash Creek Butte (17 sites) and Crater Mountain (14 sites) in northern Calif
Authors
Anthony Francis Pivarunas, Dawnika Blatter, L. J. Patrick Muffler, Michael A. Clynne, Andrew T. Calvert, Lauren N Harrison, R.L. Christiansen
Precaldera 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 h
Authors
Edward Hildreth, Judith E. Fierstein, Andrew T. Calvert
Trachyandesite 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 co
Authors
Edward Hildreth, Judith Fierstein, Fred M. Phillips, Andrew T. Calvert
Simultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc
Mapping and chronology are central to understanding spatiotemporal volcanic trends in diverse tectonic settings. The Cascades back arc in northern California (USA) hosts abundant lava flows and normal faults, but tholeiitic basalts older than 200 ka are difficult to discriminate by classic mapping methods. Paleomagnetism and chemistry offer independent means of correlating basalts, including the T
Authors
Drew T. Downs, Duane E. Champion, L. J. Patrick Muffler, Robert L. Christiansen, Michael A. Clynne, Andrew T. Calvert
The remarkable volcanism of Shastina, a stratocone segment of Mount Shasta, California
Mount Shasta, a 400 km3 volcano in northern California (United States), is the most voluminous stratocone of the Cascade arc. Most Mount Shasta lavas vented at or near the present summit; relatively smaller volumes erupted from scattered vents on the volcano’s flanks. An apron of pyroclastic and debris flows surrounds it.Shastina, a large and distinct cone on the west side of Mount Shasta, represe
Authors
Robert L. Christiansen, Andrew T. Calvert, Duane E. Champion, Cynthia A. Gardner, Judith E. Fierstein, Jorge A. Vazquez
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
Authors
Allen J. Schaen, Brian R. Jicha, Kip V. Hodges, Pieter Vermeesch, Mark E. Stelten, Cameron M. Mercer, David Phillips, Tiffany Rivera, Fred Jourdan, Erin L. Matchan, Sidney R. Hemming, Leah E. Morgan, Simon P. Kelley, William S. Cassata, Matt T. Heizler, Paulo M. Vasconcelos, Jeff A. Benowitz, Anthony A.P. Koppers, Darren F. Mark, Elizabeth M. Niespolo, Courtney J. Sprain, William E. Hames, Klaudia F. Kuiper, Brent D. Turrin, Paul R. Renne, Jake Ross, Sebastian Nomade, Hervé Guillou, Laura E. Webb, Barbara A. Cohen, Andrew T. Calvert, Nancy Joyce, Morgan Ganderød, Jan Wijbrans, Osamu Ishizuka, Huaiyu He, Adán Ramirez, Jörg Pfänder, Margarita Lopez-Martínez, Huaning Qiu, Brad S. Singer
Dextral, normal, and sinistral faulting across the eastern California shear zone-Mina deflection transition, California-Nevada
Strike-slip faults commonly include extensional and contractional bends and stepovers, whereas rotational stepovers are less common. The Volcanic Tableland, Black Mountain, and River Spring areas (California and Nevada, USA) (hereafter referred to as the VBR region) straddle the transition from the dominantly NW-striking dextral faults that define the northwestern part of the eastern California sh
Authors
Kevin DeLano, Jeffrey Lee, Rachelle Roper, Andrew T. Calvert
Temporal relationship between the Lassen Volcanic Center and mafic regional volcanism
Monogenetic volcanoes, distributed over large areas, contribute to the growth of monogenetic volcanic fields (MVFs) over thousands to millions of years of activity. It is now accepted that MVFs are also temporally clustered. To reduce uncertainties inherent to this episodic character, it is critical to combine multi-disciplinary studies to improve our knowledge of the temporal evolution of MVFs. T
Authors
Aurelie Germa, Chris Perry, Xavier Quidelleur, Andrew T. Calvert, Michael A. Clynne, Chuck Connor, Laura Connor, Rocco Malservisi, Sylvain Charbonnier
Ar-Ar age constraints on the timing of Havre Trough opening and magmatism
The age and style of opening of the Havre Trough back-arc system is uncertain due to a lack of geochronologic constraints for the region. 40Ar/39Ar dating of 19 volcanic rocks from across the southern Havre Trough and Kermadec Arc was conducted in three laboratories to provide age constraints on the system. The results are integrated and interpreted as suggesting that this subduction system is you
Authors
Richard Wysoczanski, Graham S. Leonard, James F. Gill, Ian Wright, Andrew T. Calvert, William McIntosh, Brian Jicha, John A Gamble, Christian Timm, Monica Handler, Elizabeth Kathleen Drewes, Alex Zohrab
Radiometric ages of volcanic rocks on the fort rock dome and in the aquarius mountains, Yavapai and Mohave Counties, Arizona
The Fort Rock dome, in Yavapai County, Ariz., is a roughly circular geologic structure in plan view, 2.5 km in diameter, that is similar in many ways to an impact crater; however, it is a structural dome caused by a potassic mafic intrusion at depth, and the crater-like depression in its center is erosional in origin. The Aquarius Mountains, west of the Fort Rock dome, in Mohave County, contain a
Authors
Gary S. Fuis, Andrew T. Calvert, Katie Sullivan
Pleistocene hydrothermal activity on Brokeoff volcano and in the Maidu volcanic center, Lassen Peak area, northeast California: Evolution of magmatic-hydrothermal systems on stratovolcanoes
Partially eroded stratovolcanoes worldwide, notably Mounts Rainier and Adams in the Cascades and several volcanoes in Japan, record episodic periods of eruption and geothermal activity that produce zones of hydrothermal alteration. The partly eroded core of late Pleistocene Brokeoff volcano on the south side of Lassen Peak exposes the upper 1 km of multiple ancient (ca. 410–300 ka) magmatic-hydrot
Authors
David A. John, Robert G. Lee, George N. Breit, John H. Dilles, Andrew T. Calvert, L. J. Patrick Muffler, Michael A. Clynne
Age of the dacite of Sunset Amphitheater, a voluminous Pleistocene tephra from Mount Rainier (USA), and implications for Cascade glacial stratigraphy
The dacite of Sunset Amphitheater, Mount Rainier (USA), illustrates the difficulties in establishing accurate ages of Pleistocene tephra eruptions. Nearly uniform whole-rock, glass, and mineral compositions, texture, and phenocryst assemblage establish that certain conspicuous dissected pumice exposures scattered from Mount Rainier to southern Puget Sound are products of the same Pleistocene Plini
Authors
Thomas W. Sisson, Axel K. Schmitt, Martin Danišík, Andrew T. Calvert, Napoleon Pempena, Chun-Yuan Huang, Chuan-Chou Shen
Science and Products
- Data
Dataset Establishing Temporal Duration of Two Shield Volcanoes in Northern California
This dataset contains paleomagnetic data from 30 sites at two locations in northern California (16 sites at Ash Creek Butte and 14 sites at Crater Mountain), magnetic susceptibility-temperature curves for selected samples at Ash Creek Butte, and geochemical data for map units at Crater Mountain.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 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 ol - Multimedia
- Publications
Filter Total Items: 39
Paleomagnetically defined brief lifespans for two large shield volcanoes in the Cascades Arc
Mafic to intermediate shield volcanoes with multi-cubic-kilometer eruptive volumes are common in the Cascades Volcanic Arc, but little is known about their eruptive histories as either singular or sustained episodes, or the total time required for their construction. Paleomagnetic data were collected from the lava flows of Ash Creek Butte (17 sites) and Crater Mountain (14 sites) in northern CalifAuthorsAnthony Francis Pivarunas, Dawnika Blatter, L. J. Patrick Muffler, Michael A. Clynne, Andrew T. Calvert, Lauren N Harrison, R.L. ChristiansenPrecaldera 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. CalvertSimultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc
Mapping and chronology are central to understanding spatiotemporal volcanic trends in diverse tectonic settings. The Cascades back arc in northern California (USA) hosts abundant lava flows and normal faults, but tholeiitic basalts older than 200 ka are difficult to discriminate by classic mapping methods. Paleomagnetism and chemistry offer independent means of correlating basalts, including the TAuthorsDrew T. Downs, Duane E. Champion, L. J. Patrick Muffler, Robert L. Christiansen, Michael A. Clynne, Andrew T. CalvertThe remarkable volcanism of Shastina, a stratocone segment of Mount Shasta, California
Mount Shasta, a 400 km3 volcano in northern California (United States), is the most voluminous stratocone of the Cascade arc. Most Mount Shasta lavas vented at or near the present summit; relatively smaller volumes erupted from scattered vents on the volcano’s flanks. An apron of pyroclastic and debris flows surrounds it.Shastina, a large and distinct cone on the west side of Mount Shasta, represeAuthorsRobert L. Christiansen, Andrew T. Calvert, Duane E. Champion, Cynthia A. Gardner, Judith E. Fierstein, Jorge A. VazquezInterpreting 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 raAuthorsAllen J. Schaen, Brian R. Jicha, Kip V. Hodges, Pieter Vermeesch, Mark E. Stelten, Cameron M. Mercer, David Phillips, Tiffany Rivera, Fred Jourdan, Erin L. Matchan, Sidney R. Hemming, Leah E. Morgan, Simon P. Kelley, William S. Cassata, Matt T. Heizler, Paulo M. Vasconcelos, Jeff A. Benowitz, Anthony A.P. Koppers, Darren F. Mark, Elizabeth M. Niespolo, Courtney J. Sprain, William E. Hames, Klaudia F. Kuiper, Brent D. Turrin, Paul R. Renne, Jake Ross, Sebastian Nomade, Hervé Guillou, Laura E. Webb, Barbara A. Cohen, Andrew T. Calvert, Nancy Joyce, Morgan Ganderød, Jan Wijbrans, Osamu Ishizuka, Huaiyu He, Adán Ramirez, Jörg Pfänder, Margarita Lopez-Martínez, Huaning Qiu, Brad S. SingerDextral, normal, and sinistral faulting across the eastern California shear zone-Mina deflection transition, California-Nevada
Strike-slip faults commonly include extensional and contractional bends and stepovers, whereas rotational stepovers are less common. The Volcanic Tableland, Black Mountain, and River Spring areas (California and Nevada, USA) (hereafter referred to as the VBR region) straddle the transition from the dominantly NW-striking dextral faults that define the northwestern part of the eastern California shAuthorsKevin DeLano, Jeffrey Lee, Rachelle Roper, Andrew T. CalvertTemporal relationship between the Lassen Volcanic Center and mafic regional volcanism
Monogenetic volcanoes, distributed over large areas, contribute to the growth of monogenetic volcanic fields (MVFs) over thousands to millions of years of activity. It is now accepted that MVFs are also temporally clustered. To reduce uncertainties inherent to this episodic character, it is critical to combine multi-disciplinary studies to improve our knowledge of the temporal evolution of MVFs. TAuthorsAurelie Germa, Chris Perry, Xavier Quidelleur, Andrew T. Calvert, Michael A. Clynne, Chuck Connor, Laura Connor, Rocco Malservisi, Sylvain CharbonnierAr-Ar age constraints on the timing of Havre Trough opening and magmatism
The age and style of opening of the Havre Trough back-arc system is uncertain due to a lack of geochronologic constraints for the region. 40Ar/39Ar dating of 19 volcanic rocks from across the southern Havre Trough and Kermadec Arc was conducted in three laboratories to provide age constraints on the system. The results are integrated and interpreted as suggesting that this subduction system is youAuthorsRichard Wysoczanski, Graham S. Leonard, James F. Gill, Ian Wright, Andrew T. Calvert, William McIntosh, Brian Jicha, John A Gamble, Christian Timm, Monica Handler, Elizabeth Kathleen Drewes, Alex ZohrabRadiometric ages of volcanic rocks on the fort rock dome and in the aquarius mountains, Yavapai and Mohave Counties, Arizona
The Fort Rock dome, in Yavapai County, Ariz., is a roughly circular geologic structure in plan view, 2.5 km in diameter, that is similar in many ways to an impact crater; however, it is a structural dome caused by a potassic mafic intrusion at depth, and the crater-like depression in its center is erosional in origin. The Aquarius Mountains, west of the Fort Rock dome, in Mohave County, contain aAuthorsGary S. Fuis, Andrew T. Calvert, Katie SullivanPleistocene hydrothermal activity on Brokeoff volcano and in the Maidu volcanic center, Lassen Peak area, northeast California: Evolution of magmatic-hydrothermal systems on stratovolcanoes
Partially eroded stratovolcanoes worldwide, notably Mounts Rainier and Adams in the Cascades and several volcanoes in Japan, record episodic periods of eruption and geothermal activity that produce zones of hydrothermal alteration. The partly eroded core of late Pleistocene Brokeoff volcano on the south side of Lassen Peak exposes the upper 1 km of multiple ancient (ca. 410–300 ka) magmatic-hydrotAuthorsDavid A. John, Robert G. Lee, George N. Breit, John H. Dilles, Andrew T. Calvert, L. J. Patrick Muffler, Michael A. ClynneAge of the dacite of Sunset Amphitheater, a voluminous Pleistocene tephra from Mount Rainier (USA), and implications for Cascade glacial stratigraphy
The dacite of Sunset Amphitheater, Mount Rainier (USA), illustrates the difficulties in establishing accurate ages of Pleistocene tephra eruptions. Nearly uniform whole-rock, glass, and mineral compositions, texture, and phenocryst assemblage establish that certain conspicuous dissected pumice exposures scattered from Mount Rainier to southern Puget Sound are products of the same Pleistocene PliniAuthorsThomas W. Sisson, Axel K. Schmitt, Martin Danišík, Andrew T. Calvert, Napoleon Pempena, Chun-Yuan Huang, Chuan-Chou Shen - News