The east face of Middle Sister is 350 m (1150 ft) high. Ice-sculpted pile of lavas at right, variously called "Black Hump," "Prouty Point," or "Step Sister," has 190 m of relief and consists of at least five flows.
Andrew Todd Calvert, Ph.D.
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
Argon geochronology results for Reconnaissance basement geology and tectonics of North Zealandia
Dataset Establishing Temporal Duration of Two Shield Volcanoes in Northern California
Database for the Geologic Map of Three Sisters Volcanic Cluster, Cascade Range, Oregon
Chemical and isotopic analyses of Mount Shasta, California
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
The east face of Middle Sister is 350 m (1150 ft) high. Ice-sculpted pile of lavas at right, variously called "Black Hump," "Prouty Point," or "Step Sister," has 190 m of relief and consists of at least five flows.
Aerial photo of Mount Shasta's southwestern flank in a low-snow period. The Hotlum cone is on the right, while the Shastina dome is to the left.
Aerial photo of Mount Shasta's southwestern flank in a low-snow period. The Hotlum cone is on the right, while the Shastina dome is to the left.
Active volcanism on the Arabian Shield—Geology, volcanology, and geophysics of northern Harrat Rahat and vicinity, Kingdom of Saudi Arabia
The Saudi Geological Survey-U.S. Geological Survey northern Harrat Rahat project—Styles, rates, causes, and hazards of volcanism near Al Madīnah al Munawwarah, Kingdom of Saudi Arabia
Cenozoic tectonics of the western Arabia Plate related to harrat magmatism near Al Madīnah, Kingdom of Saudi Arabia
Eruptive history of northern Harrat Rahat—Volume, timing, and composition of volcanism over the past 1.2 million years
The duration and characteristics of magmatic differentiation from basalt to trachyte within the Matan volcanic center, northern Harrat Rahat, Kingdom of Saudi Arabia
Explosive trachyte eruptions from the Al Efairia volcanic center in northern Harrat Rahat, Kingdom of Saudi Arabia
Mantle origin and crustal differentiation of basalts and hawaiites of northern Harrat Rahat, Kingdom of Saudi Arabia
Paleomagnetically defined brief lifespans for two large shield volcanoes in the Cascades Arc
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
Simultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc
The remarkable volcanism of Shastina, a stratocone segment of Mount Shasta, California
Science and Products
- Data
Argon geochronology results for Reconnaissance basement geology and tectonics of North Zealandia
The data are the results of mass spectrometer experiments to measure 40Ar/39Ar ages of groundmass and mineral separates from volcanic rocks in offshore New Zealand. The data were collected using a MAP216 noble gas mass spectrometer at the USGS facility in Menlo Park, CaliforniaDataset 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 sediChemical and isotopic analyses of Mount Shasta, California
The dataset consists of chemical analyses and some isotopic analyses of rock samples collected from Mount Shasta, California, and its immediate surroundings. - 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
Middle Sister volcano's east face with shingled stacks of thin lava...Middle Sister volcano's east face with shingled stacks of thin lava...
The east face of Middle Sister is 350 m (1150 ft) high. Ice-sculpted pile of lavas at right, variously called "Black Hump," "Prouty Point," or "Step Sister," has 190 m of relief and consists of at least five flows.
The east face of Middle Sister is 350 m (1150 ft) high. Ice-sculpted pile of lavas at right, variously called "Black Hump," "Prouty Point," or "Step Sister," has 190 m of relief and consists of at least five flows.
Mount Shasta, CAAerial photo of Mount Shasta's southwestern flank in a low-snow period. The Hotlum cone is on the right, while the Shastina dome is to the left.
Aerial photo of Mount Shasta's southwestern flank in a low-snow period. The Hotlum cone is on the right, while the Shastina dome is to the left.
- Publications
Filter Total Items: 46
Active volcanism on the Arabian Shield—Geology, volcanology, and geophysics of northern Harrat Rahat and vicinity, Kingdom of Saudi Arabia
Active volcanic systems pose serious hazards to people and property including inundation and incineration by lava, blanketing by tephra (volcanic ash), exposure to noxious volcanic gases, and damage from shallow earthquakes triggered by ascending molten material (magma). To improve understanding of volcanism and associated seismicity on the western Arabia Plate, the Saudi Geological Survey and theThe Saudi Geological Survey-U.S. Geological Survey northern Harrat Rahat project—Styles, rates, causes, and hazards of volcanism near Al Madīnah al Munawwarah, Kingdom of Saudi Arabia
Active volcanic systems pose serious hazards to people and property including inundation and incineration by lava, blanketing by tephra (volcanic ash), exposure to noxious volcanic gases, and damage from shallow earthquakes triggered by ascending molten material (magma). To improve understanding of volcanism and associated seismicity on the western Arabia Plate, the Saudi Geological Survey and theAuthorsThomas W. Sisson, Andrew T. Calvert, Walter D. MooneyCenozoic tectonics of the western Arabia Plate related to harrat magmatism near Al Madīnah, Kingdom of Saudi Arabia
Sprawling volcanic fields, or harrats, in western Saudi Arabia have been emplaced during the past 30 million years following effusions of flood basalts in Ethiopia and Yemen. Although broadly associated with volcanism in three rift valleys (Red Sea, Gulf of Aden, and East African Rift Zone) radiating from the Afar depression, harrat abundance on the Arabian Peninsula indicates that volcanism is diAuthorsAndrew T. Calvert, Thomas W. SissonEruptive history of northern Harrat Rahat—Volume, timing, and composition of volcanism over the past 1.2 million years
Harrat Rahat, one of several large, basalt-dominated volcanic fields in the western part of the Kingdom of Saudi Arabia, is a prime example of continental, intraplate volcanism. Excellent exposure makes this an outstanding site to investigate changing volcanic flux and composition through time. We present 93 40Ar/39Ar ages and 6 36Cl surface-exposure ages for volcanic deposits throughout northernAuthorsMark E. Stelten, Drew T. Downs, Duane E. Champion, Hannah R. Dietterich, Andrew T. Calvert, Thomas W. Sisson, Gail A. Mahood, Hani M. ZahranThe duration and characteristics of magmatic differentiation from basalt to trachyte within the Matan volcanic center, northern Harrat Rahat, Kingdom of Saudi Arabia
A fundamental goal of igneous petrology is to quantify the durations 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 we preseAuthorsMark E. Stelten, Drew T. Downs, Hannah R. Dietterich, Gail A. Mahood, Andrew T. Calvert, Thomas W. Sisson, Molly R. Witter, Hani M. Zahran, Jamal ShawaliExplosive trachyte eruptions from the Al Efairia volcanic center in northern Harrat Rahat, Kingdom of Saudi Arabia
Harrat Rahat is an alkali basalt, continental, intraplate volcanic field located within the central-western part of the Kingdom of Saudi Arabia. The northern quarter of Harrat Rahat contains evolved volcanic products that achieve trachyte compositions (>60 weight percent SiO2). Within the Al Efairia volcanic center, pyroclastic-flow and -surge deposits that reflect explosive trachyte volcanism (anAuthorsDrew T. Downs, Mark E. Stelten, Hannah R. Dietterich, Duane E. Champion, Gail A. Mahood, Thomas W. Sisson, Andrew T. Calvert, Jamal ShawaliMantle origin and crustal differentiation of basalts and hawaiites of northern Harrat Rahat, Kingdom of Saudi Arabia
Quaternary volcanic rocks of northern Harrat Rahat, Kingdom of Saudi Arabia, are chiefly alkali basalts with subordinate transitional basalts, hawaiites, mugearites, benmoreites, and trachytes. Geochemical and isotopic results indicate that crystallization-differentiation, mixing, and cumulate reassimilation within the magmatic system produced most of its compositional diversity, with only minor iAuthorsThomas W. Sisson, Drew T. Downs, Andrew T. Calvert, Hannah R. Dietterich, Gail A. Mahood, Vincent J.M. Salters, Mark E. Stelten, Jamal ShawaliPaleomagnetically 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. Vazquez - News