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The map displays volcanoes, earthquakes, monitoring instruments, and past lava flows.

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Volcano Hazards Program

Find U.S. Volcano

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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Volcano Activity Notifications

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

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

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

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

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

New open access articles on Mauna Loa 2022 eruption

New open access articles on Mauna Loa 2022 eruption

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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
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Volcano Hazards Program, Volcano Science Center

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
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Volcano Hazards Program, Volcano Science Center

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
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Volcano Hazards Program, Volcano Science Center
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Petrologic and Stratigraphic Studies

Silicate MI can record a variety of magmatic processes that control the evolution of igneous systems. The following subsections briefly list relevant tools and techniques (+ appropriate references) that have been used to study mixing, crystallization, and other phenomena of interest to workers undertaking a study of a magma-hydrothermal system.

MAGMA MIXING AND CRYSTAL FRACTIONATION

Silicate MI may be useful indicators of magma mixing, particularly when a rock has undergone some alteration or extensive crystallization of the groundmass. Under such circumstances, the MI may remain as reliable indicators of melt compositions during magmatic crystallization. Hervig & Dunbar (1992) studied both the Bishop and Bandelier magmatic systems, and used MI as evidence that magma mixing was an important process in producing the zonation within both of these magma bodies. Their data for MI of the Lower Bandelier tuff can be divided into two groups. Matrix glass plots within the less-differentiated group; this is inconsistent with crystal fractionation, wherein the matrix should represent the most differentiated composition. The data were interpreted to indicate mixing between low- and high-Ti melts. In earlier studies, Anderson (1976) and Rhodes et al. (1979) used MI as evidence for mixing events during the formation of andesitic magmas and ocean-floor basalts, respectively. Halsor (1989) studied large clear MI within plagioclase from andesites erupted at Toliman volcano in Guatemala. He concluded that MI were not in equilibrium with either bulk rock or matrix liquid, and that a mixing event caused rapid growth of the plagioclase and entrapment of large MI.

Crystallization and fractionation may be recorded by the compositions of a suite of MI trapped at different times. As opposed to mixing trends, which are linear on trace-element scatter plots, crystallization will result in data trends that are curved for compatible elements. Differentiation may be observed by analysis of MI within a single crystal or a group of phenocrysts. Lu et al. (1992) used trace-element concentrations in MI to calculate the amount of crystal fractionation during crystallization of the Bishop tuff magma. Vaggelli et al. (1993) used changes in MI compositions between cores and rims of clinopyroxene crystals as evidence for crystal fractionation in recent Vesuvius lavas.

EXPERIMENTAL PETROLOGY

Because MI approach constant-volume closed systems, they can be used as experimental pressure vessels for high-temperature petrological experiments. In effect, most homogenization experiments are exercises in experimental petrology. Pressure in the inclusion is a function of temperature (Fig. 4) and can be varied by means of a heating stage or furnace. Ideally, one can determine the solidus and liquidus of magmas by heating naturally crystallized inclusions. Clocchiatti & Massare (1985) used silicate MI within plagioclase as experimental vessels that they could monitor as a function of equilibration temperature. By doing experiments at different temperatures on separate groups of MI, they were able to replicate melt and phenocryst compositions obtained with high-pressure experimental apparata on similar tholeiite compositions. Roedder (1976) presented similar thermometric data on MI from lunar and Hawaiian basalts, though without EPMA analyses of the "run products." Roedder (1972) performed laboratory experiments on MI to estimate magmatic conditions during formation of Ascension Island trachytes.

STRATIGRAPHIC CORRELATIONS

One of the most recent uses of MI has been the correlation of tonsteins, or bentonized ash-beds within ancient lithologic sequences. Because the volcanic ash has been completely altered to clay, whole rock compositions and glass shard compositions cannot be used for stratigraphic correlations. However, Delano et al. (1994) were able to use MI to differentiate a variety of individual units and to define regional-scale stratigraphic time-planes. Even though they studied Ordovician rocks, the inclusions were still glassy and seemingly unaltered. Economic geologists can use MI to define the stratigraphy of mineralized terrains and to correlate units in highly altered areas. Potentially, MI can be used to study the mass balance of bentonite-style (or any other kind of) alteration or to characterize the volatile concentrations in ancient eruptive sequences (Webster et al. 1994).