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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.

Learn more about NVEWS

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

Volcano Watch — The 1969 Maunaulu eruption: 12 lava fountaining episodes

Volcano Watch — The 1969 Maunaulu eruption: 12 lava fountaining episodes

Photo & Video Chronology — January 12, 2026 — Kīlauea episode 40

Photo & Video Chronology — January 12, 2026 — Kīlauea episode 40

Volcano Watch — Hau’oli Makahiki Hou: a round-up of fireworks from Kīlauea’s fountains

Volcano Watch — Hau’oli Makahiki Hou: a round-up of fireworks from Kīlauea’s fountains

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Publications

The magmatic-hydrothermal system of the Three Sisters volcanic cluster, Oregon, imaged from field gravity measurements The magmatic-hydrothermal system of the Three Sisters volcanic cluster, Oregon, imaged from field gravity measurements

From 2019 to 2024, gravity surveys were conducted at the Three Sisters volcanic cluster (TSVC), measuring 246 gravity sites using a spring relative gravimeter. We calculated the residual Bouguer anomaly and identified three main zones with negative anomalies, ranging from −4 to −8 mGal, located southwest and west of South Sister, within an area that has been uplifting for the past two...
Authors
Helene Le Mevel, Nathan Lee Andersen, Annika E. Dechert, Josef Dufek
By
Volcano Hazards Program, Volcano Science Center

The anatomy and lethality of the Siberian Traps large igneous province The anatomy and lethality of the Siberian Traps large igneous province

Emplacement of the Siberian Traps large igneous province (LIP) around 252 Ma coincided with the most profound environmental disruption of the past 500 million years. The enormous volume of the Siberian Traps, its ability to generate greenhouse gases and other volatiles, and a temporal coincidence with extinction all suggest a causal link. Patterns of marine and terrestrial extinction...
Authors
Seth D. Burgess, Benjamin A. Black
By
Volcano Hazards Program, Volcano Science Center

Mitigation of human cognitive bias in volcanic eruption forecasting Mitigation of human cognitive bias in volcanic eruption forecasting

Modern operational eruption forecasting methods rely heavily on human judgment in the face of uncertainty and are thus susceptible to myriad cognitive biases and errors by the scientist-forecasters. Recent developments in the behavioral sciences have elucidated cognitive biases across a wide spectrum of human behaviors and found ways to mitigate them. These insights have led to...
Authors
Heather M. Wright, J. D. Pesicek, Stephen A. Spiller
By
Volcano Hazards Program, Volcano Science Center
View All
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About Melt Inclusions

Silicate-melt inclusions (MI) are small (~1-300 µm) blebs of silicate melt that are trapped within igneous phenocrysts (Fig. 1). They are glassy or crystalline, and are found within both extrusive and intrusive rocks. Because they can form at high pressures and are contained within relatively incompressible phenocryst hosts, they may retain high concentrations of volatile elements that normally escape from magmas during degassing. As such, analysis of these inclusions provides direct information on the volatile contents of magmatic systems.

Figure 1. Transmitted-light photomicrographs of inclusions in quartz.

 

Figure 1. Transmitted-light photomicrographs of inclusions in quartz. (A) Silicate MI with negative crystal shape that reflects the bipyramidal habit of the host quartz. Note large (shrinkage?) bubble. From the Dolomite Mts. (Clochiatti 1975). (B) Multiple elongate silicate MI, most without bubbles, in quartz from Mont Dore (from Clocchiatti 1975). Field is 700 µm across. (C) Crystallized MI in quartz from Pantelleria (from Lowenstern & Mahood, 1991). Letter "q" shows quartz host, whereas "i" denotes inclusion. (D) The same MI after heating the host quartz for several hours at 850°C and atmospheric pressure. The inclusion is glassy and contains one very small bubble. (E) Three glassy, bubble-free MI of various sizes from Plinian fallout of the tuff of Pine Grove, Utah. (F) An empty inclusion (void) in quartz from the Plinian fallout of the tuff of Pine Grove. Such features are interpreted here to be leaked fluid inclusions that originally contained magmatic fluid/vapor, but no silicate melt (see section on Evidence for Trapped Fluids.

 

A number of recent papers have used silicate MI to understand magma degassing, to characterize the compositions of immiscible fluids separating from magmas, and to study petrogenetic processes such as magma mixing and crystal fractionation. Their use has allowed greater understanding of igneous geochemistry and magmatic processes (Table 1). This paper reviews the nature and characteristics of silicate MI, the tools and methods for their analysis, and some important findings of recent studies.

Several previous reviews have also addressed the general topic of MI and the interested reader is referred to these works. Clocchiatti (1975) reviewed optical and thermometric studies of MI in quartz and provides abundant observational and experimental data on the behavior of MI. Sobolev & Kostyuk (1975) synthesized the considerable volume of Russian literature on MI accumulated prior to 1975. Roedder (1979) gave a thorough discussion of silicate MI, their origins, and the methods of study and work to that date. Much of this information is repeated in his later, more general volume on fluid inclusions (Roedder 1984). Roedder (1992) summarized evidence for immiscible fluids in the magmatic environment. Johnson et al. (1994) discussed MI, and the information they provide about the pre-eruptive volatile contents of four magmatic systems; Kilauea, Mt. St. Helens, the Bishop tuff, and Mt. Pinatubo.

My review focuses on inclusions from andesitic to rhyolitic magmas and concentrates on those studies with information useful to economic geologists and hydrothermal geochemists who seek understanding of fluids emanating from igneous systems. The review consists of two parts; it begins with a primer on the characteristics of MI and methods by which they can be studied. The second half concentrates on recent studies and applications for petrologists and economic geologists.

Table 1. Data Obtainable and Not Obtainable from Silicate-Melt Inclusions

I. DATA OBTAINABLE FROM MI

1. Dissolved volatile concentrations in ore-forming and other magmas; H2O, CO2, Cl, S, F, B, Li and ore metals (See Table 2).

2. Minimum pressure of crystallization (e.g., Anderson et al. 1989).

3. Approximate temperature during crystallization (See Roedder 1984).

4. Evidence for exsolved fluids during crystallization of phenocrysts (e.g., Lowenstern 1994a).

5. Approximate (and partial) composition of coexisting exsolved fluids (e.g., Anderson et al. 1989; Wallace & Gerlach 1994; Lowenstern 1994b).

6. Evidence for magma mixing (e.g., Anderson 1976).

7. Composition of the melt phase in granites (Frezzotti 1992).

8. Time-scale of magmatism/volcanism (e.g., Bogaard & Schirink 1994).

II. DATA NOT OBTAINABLE FROM MI

1. The composition of the bulk magma (i.e., melt + phenocrysts + exsolved fluid).

2. Maximum pressure (depth) of entrapment.

3. Fate of fluids exsolved from the magma; mechanisms for fluid egress from magma.

4. Role of magma in formation of epithermal ore deposits (at least little direct information is available from silicate MI).

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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.

Learn more about NVEWS

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. 

Get Latest Updates

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.

View Assessments

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.

Learn More

News

Volcano Watch — The 1969 Maunaulu eruption: 12 lava fountaining episodes

Volcano Watch — The 1969 Maunaulu eruption: 12 lava fountaining episodes

Photo & Video Chronology — January 12, 2026 — Kīlauea episode 40

Photo & Video Chronology — January 12, 2026 — Kīlauea episode 40

Volcano Watch — Hau’oli Makahiki Hou: a round-up of fireworks from Kīlauea’s fountains

Volcano Watch — Hau’oli Makahiki Hou: a round-up of fireworks from Kīlauea’s fountains

View All

Publications

The magmatic-hydrothermal system of the Three Sisters volcanic cluster, Oregon, imaged from field gravity measurements The magmatic-hydrothermal system of the Three Sisters volcanic cluster, Oregon, imaged from field gravity measurements

From 2019 to 2024, gravity surveys were conducted at the Three Sisters volcanic cluster (TSVC), measuring 246 gravity sites using a spring relative gravimeter. We calculated the residual Bouguer anomaly and identified three main zones with negative anomalies, ranging from −4 to −8 mGal, located southwest and west of South Sister, within an area that has been uplifting for the past two...
Authors
Helene Le Mevel, Nathan Lee Andersen, Annika E. Dechert, Josef Dufek
By
Volcano Hazards Program, Volcano Science Center

The anatomy and lethality of the Siberian Traps large igneous province The anatomy and lethality of the Siberian Traps large igneous province

Emplacement of the Siberian Traps large igneous province (LIP) around 252 Ma coincided with the most profound environmental disruption of the past 500 million years. The enormous volume of the Siberian Traps, its ability to generate greenhouse gases and other volatiles, and a temporal coincidence with extinction all suggest a causal link. Patterns of marine and terrestrial extinction...
Authors
Seth D. Burgess, Benjamin A. Black
By
Volcano Hazards Program, Volcano Science Center

Mitigation of human cognitive bias in volcanic eruption forecasting Mitigation of human cognitive bias in volcanic eruption forecasting

Modern operational eruption forecasting methods rely heavily on human judgment in the face of uncertainty and are thus susceptible to myriad cognitive biases and errors by the scientist-forecasters. Recent developments in the behavioral sciences have elucidated cognitive biases across a wide spectrum of human behaviors and found ways to mitigate them. These insights have led to...
Authors
Heather M. Wright, J. D. Pesicek, Stephen A. Spiller
By
Volcano Hazards Program, Volcano Science Center
View All
Was this page helpful?