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Volcano Hazards Program

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There are about 170 potentially active volcanoes in the U.S. The mission of the USGS Volcano Hazards Program is to enhance public safety and minimize social and economic disruption from volcanic unrest and eruption through our National Volcano Early Warning System. We deliver forecasts, warnings, and information about volcano hazards based on a scientific understanding of volcanic behavior.

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Ash-rich plume rises out of Halemaʻumaʻu Crater, Kilauea Volcano Hawaiʻi

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Volcano Hazards Assessments

Mount Rainier seen from Puyallup, Washington

Long-term hazards assessments identify locations at risk from volcanic hazards. They are released as high-resolution hazards-zonation maps with accompanying explanations, which help guide eruption preparedness plans.

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U.S. Volcano Observatories

Volcano Observatory staff monitor, research, and issue formal notices of activity for volcanoes in assigned geographic areas. Scientists also assess volcano hazards and work with communities to prepare for volcanic eruptions.

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April 9, 2026

Photo & Video Chronology — April 9, 2026 — Kīlauea summit episode 44

April 9, 2026

Volcano Watch — Caldera clues: tephra deposits from Kīlauea’s past

April 8, 2026

New open access articles on Mauna Loa 2022 eruption

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April 9, 2026

Yellowstone Volcano Observatory 2024 annual report Yellowstone Volcano Observatory 2024 annual report

The Yellowstone Volcano Observatory (YVO) monitors volcanic and hydrothermal activity associated with the Yellowstone magmatic system, carries out research into magmatic processes occurring beneath Yellowstone Caldera, and issues timely warnings and guidance related to potential future geologic hazards. YVO is a collaborative consortium that includes the U.S. Geological Survey (USGS)...

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Yellowstone Volcano Observatory

Volcano Hazards Program, Volcano Science Center

March 31, 2026

Determining Volcanic Risk in Auckland (DEVORA) Research Programme—A transdisciplinary approach to address the challenge of distributed volcanism in an urban environment Determining Volcanic Risk in Auckland (DEVORA) Research Programme—A transdisciplinary approach to address the challenge of distributed volcanism in an urban environment

The Determining Volcanic Risk in Auckland (DEVORA) Research Programme was launched in 2008 to address the challenges associated with monogenetic volcanism in an urban setting and to enhance volcanic risk management in Tāmaki Makaurau Auckland in Aotearoa New Zealand. It is a multi-agency, increasingly transdisciplinary (defined here as research that transcends traditional disciplinary...

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Jan M. Lindsay, Elaine R. Smid, Natalie Balfour, Natalia I. Deligne, Angela Doherty, Annahlise Hall, Tracy Howe, Gill Jolly, Graham Leonard, Kate Lewis, Craig A. Miller, Ema Nersezova, Ross Roberts, Richard E. Smith, Thomas Stolberger, Kelvin Tapuke, Thomas M. Wilson

Volcano Hazards Program, Volcano Science Center

March 26, 2026

Advances in volcano monitoring driven by the first decade of Sentinel-1 observations Advances in volcano monitoring driven by the first decade of Sentinel-1 observations

Sentinel-1 has transformed how satellite radar data (SAR and InSAR) are used in volcanology. The systematic, long-term archive and open-access policy means that volcano observatories and research organisations have invested in integrating Sentinel-1 datasets into their monitoring systems. We identify 233 high priority volcanoes and estimate that Sentinel-1 data has been used in peer...

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Juliet Biggs, Nantheera Anantrasirichai, Kyle R. Anderson, Valerie Cayol, Edna W. Dualeh, Quentin Dumont, Susanna K. Ebmeier, Jean Luc Froger, Matthew Gaddes, Federico Galleto, Pablo J. Gonzales, Ian Hamling, Andrew Hooper, Milan Lazecky, Camila Novoa Lizama, Matthew E. Pritchard

Volcano Hazards Program, Volcano Science Center

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Melt Inclusions in Granites and Xenolithic Ejecta

For the most part, MI are absent in granitic rocks because their prolonged cooling history allows complete crystallization of the inclusions, erasing any record of their existence (Tuttle 1952). Only in rapidly cooled intrusions will MI remain intact and unaltered. In the ~280-Ma Mount Genis granite in southeastern Sardinia, Frezzotti (1992) found MI (some glassy) within equigranular granites as well as in crystals lining miarolitic cavities. Coexisting brine was interpreted as having formed during the late stages of crystallization of the magma. The MI were analyzed by EPMA, and several of them contained typical high-silica rhyolite glass with Cl concentrations reflecting equilibrium with vapor and hydrosaline melt (Shinohara 1994). Hansteen & Lustenhouwer (1990) examined MI and coexisting aqueous inclusions from the Permian Eikeren-Skrim granite in Norway. The inclusions homogenized at 685-705 °C, were composed of rhyolitic and rhyodacitic glass (not peralkaline) and were trapped at the same time as a saline aqueous fluid. Eadington & Nashar (1978) described and analyzed glass inclusions from topaz-quartz rocks from the New England district of New South Wales in Australia. Many of the MI contained several wt.% F, as well as apparent high H2O concentrations. Weisbrod (1981) reviewed several studies of coexisting fluid and melt inclusions in shallow intrusions and porphyry deposits. Takenouchi & Imai (1975) described MI from a variety of porphyry and volcanic rocks and observed the effects of cooling history on the characteristics of MI.

Occasionally, intrusive rocks are ejected as xenoliths during volcanic eruptions. Studies of such samples have often resulted in discovery of CO2-rich fluids in equilibrium with melt in the environment where the xenoliths grew (Roedder 1965; Belkin et al. 1985; Frezzotti et al. 1991; Belkin and De Vivo 1993). Other xenoliths show evidence for immiscibility between silicate melt and hypersaline fluids (Roedder & Coombs 1967) or entrapment of both phases, though at different times (De Vivo et al. 1993).

Summary

Silicate MI contain information on the dissolved volatile concentrations in igneous rocks (Tables 2 and 3). A variety of analytical and thermometric methods can be used to extract information from MI, as regards magmatic volatile concentrations, the compositions of exsolved magmatic fluids and the pressure and temperature conditions under which magmas undergo crystallization. New techniques promise to increase the number of possible uses of MI, lengthening the first half of Table 1 and shortening its last half. For example, given improving microbeam techniques, MI may contribute new data on the stable-isotopic (H, O, S, Cl) composition of non-degassed magmas, and the effect of degassing on the isotopic composition of silicate melt. New microbeam dating methods may allow assessment of the time delay between crystallization (MI formation) and eruption. Combined with the ever-increasing data-set on volatile solubilities, MI may yield more reliable estimates of the depths to magma chambers than are currently available through mineral geobarometers. As such, MI are likely to remain one of the most useful and reliable methods for understanding the behavior of volatile components in igneous systems and will continue to provide insight for economic geologists, volcanologists and other geoscientists.

Acknowledgements

Discussions over the past 7 years have helped me to clarify my thinking about MI; I thank A.T. Anderson, C.R. Bacon, D.K. Bird, P. Fiske, G.A. Mahood, S. Newman, E. Roedder, H. Shinohara, T. Sisson, J. Stebbins, and P.J. Wallace for their input. The rest of my education about MI has been the legacy of excellent papers by A.T. Anderson, E. Roedder, R. Clocchiatti and others, as well as the interesting samples I've had the good fortune to study. I appreciate reviews of the manuscript and helpful comments by C. Bacon, K. Bargar, H. Belkin, B. Bodnar, J. Hedenquist, H. Shinohara, and S. Simmons.

Volcano Hazards Program | U.S. Geological Survey

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Volcano Hazards Program

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Volcano Activity Notifications

USGS Volcano Observatories release regular updates and notifications to communicate increases or decreases in volcanic activity and explain unusual or hazardous circumstances.

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