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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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News

February 26, 2026

Volcano Watch — Mauna Loa has lessons to teach during quiet times

February 17, 2026

Photo & Video Chronology — February 16, 2026 — Kīlauea episode 42 fountains and fallout

February 5, 2026

Volcano Watch — New Hawaii citizen science tool: Is Tephra Falling?

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Publications

March 2, 2026

Forecasting volcanic activity in Germany—A multi-criteria approach Forecasting volcanic activity in Germany—A multi-criteria approach

Igneous activity, including shallow intrusions and volcanism, has the potential to disrupt underground critical infrastructure. Notably, future underground infrastructure projects like high-level radioactive waste repositories must be sited in areas of extremely low disruption probability by igneous activity. In Germany, according to the Repository Site Selection Act of 2017...

Authors

A. Bartels, L.H. Rummel, F. Mayle

Volcano Hazards Program, Volcano Science Center

February 18, 2026

A comparison of non-contact methods for measuring turbidity in the Colorado River A comparison of non-contact methods for measuring turbidity in the Colorado River

Monitoring suspended-sediment concentration (SSC) is essential to better understand how sediment transport could adversely affect water availability for human communities and ecosystems. Aquatic remote sensing methods are increasingly utilized to estimate SSC and turbidity in rivers; however, an evaluation of their quantitative performance is limited. This study evaluates the performance...

Authors

Natalie K. Day, Tyler V. King, Adam R. Mosbrucker

Volcano Hazards Program, Volcano Science Center, Colorado Water Science Center, Idaho Water Science Center, Cascades Volcano Observatory

January 27, 2026

Toward a four-dimensional petrogenetic model of a distributed volcanic field on the southern edge of the Colorado Plateau Toward a four-dimensional petrogenetic model of a distributed volcanic field on the southern edge of the Colorado Plateau

A detailed characterization of the >3,000 square kilometer (km2) Springerville volcanic field, located on the southern tip of the Colorado Plateau in Arizona, United States, with its more than 501 volcanic units and widely distributed >420 cinder cones and lava flows, provides constraints toward an integrated petrogenetic model for the field. Large-volume effusive tholeiitic eruptions at...

Authors

Marissa E. Mnich, Christopher D. Condit

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).