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

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

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

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

Volcano Watch — What do small earthquakes beneath Kīlauea summit mean for the ongoing eruption?

Volcano Watch — What do small earthquakes beneath Kīlauea summit mean for the ongoing eruption?

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

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
By
Volcano Hazards Program, Volcano Science Center

Luminescence dating of hydrothermal explosions in the Yellowstone Plateau volcanic field Luminescence dating of hydrothermal explosions in the Yellowstone Plateau volcanic field

Hydrothermal explosions are a significant geological hazard in some active volcanic systems; however, the timing and triggering mechanisms of these explosions are poorly constrained. This study applies luminescence dating techniques to hydrothermal explosion deposits in the Yellowstone Plateau volcanic field to constrain explosion chronologies and evaluate potential triggering mechanisms...
Authors
Karissa Cordero, Nathan Brown, Lauren N. Harrison, Shaul Hurwitz
By
Volcano Hazards Program, Volcano Science Center
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Dissolved Volatile Concentrations in Melt Inclusions

One of the primary goals of most modern studies of MI has been to determine the amounts of dissolved volatiles present within crystallizing magmas. Most studies have concentrated on volcanic rocks, as they are often pristine and unaffected by post-entrapment phenomena such as leaking and crystallization. Table 2 lists studies that have determined the concentrations of dissolved volatiles in MI from silicic magmas such as dacites and rhyolites, compositions typically associated with hydrothermal ore-forming systems.

Table 2. Volatile concentrations in a variety of recently studied silicic magmas, as determined by analysis of silicate MI.

UNIT
REFERENCE

SiO2 in melt (wt.%)

H2O (wt.%)

F (wt.%)

Cl (wt.%)

S (ppm)

CO2 (ppm#)

Taupo Vol. Zone, NZ

Dunbar et al. (1989)

.h

.

.

.

.

.

   Taupo, 2ka

"

73

4.3

0.0045

0.17

<200

-

   Hatepe, 2ka

"

76

4.3

0.0043

0.17

<200

-

   Okaia, ~22ka

"

-

5.9

0.047

0.21

<200

-

Pine Grove, USA 22Ma

Lowenstern (1994b)

77

6.0 - 8.0

0.358

0.062

<60

Up to 970

Taylor Creek, USA

Webster & Duffield (1994)

70

<2.0

0.15- 3.9

0.23-0.37

-

-

Galeras, Col. 1991-92

Stix et al. (1993)

-

-

0.02 -0.1

0.09-0.25

50

-

Toba, Indonesia, 75ka

Newman & Chesner (1989)

76

5.2-5.7

-

-

-

<100

Santa Maria 1902

Palais & Sigursson (1989)

69

-

-

0.139

200

-

Santa Maria 1902

Roggensack et al. (1993) Ý

73

4.2

-

0.13

300

-

Mt. St. Helens 1530

Palais & Sigursson (1989)

71

-

-

0.077

70

-

Mt. St. Helens 1980

Rutherford et al. (1985)

73.5

4.6±1.0

-

0.10±.03

100±100

-

Nevado del Ruiz, 1985

Layne et al. (1992)

70-74

1.6- 3.3

0.05-0.14

0.01-0.18

-

-

Lower Bandelier Tuff

Dunbar & Hervig (1992a)

  .

  .

.  

.  

. 

. 

   Plinian

"

76-77

4.0- 5.5

0.2-0.3

0.2-0.25

-

-

   Basal Ignimbrite

"

76-77

3.0- 4.0

0.1-0.2

0.15-0.25

-

-

   Main Body Ignimbrite

"

76-77

2.0- 3.0

0.05-0.15

0.1-0.25

-

-

Katmai, AK USA 1912

Lowenstern, 1993

77

3.4- 4.2

-

-

-

<50

Katmai, AK USA 1912

Westrich et al. 1991

.

.

.

.

.

.

   Rhyolite

"

77

3.8

0.063

0.193

<65

-

   Dacite

"

77

2.3

0.064

0.179

120

-

   Andesite

"

74

1.0

0.053

0.169

170

-

Crater Lake, OR, USA

Bacon et al. (1992)

.

.

.

.

.

.

   Climactic: 6450 ybp

"

73

3.9

0.04

0.188

-

<25

   Cleetwood Flow, OR

"

.

5.3

0.03-0.05

0.09-0.14

-

<25

   Llao Rock, OR

"

.

3.8- 4.7

0.03-0.07

0.18-0.21

-

<25

Mt. Pinatubo Phillip.

Wallace & Gerlach (1994)

.

.

.

.

.

.

June 15, 1991

Gerlach et al. (1997)

.

.

.

.

.

.

Bishop tuff CA US 740ka

. .

.

.

.

.

.

.

  Plinian

Anderson et al. (1989)

77

5.1- 6.8

-

0.08

-

up to 190

  Early Ignimbrites

Skirius et al. (1990)

77

5.0- 6.9

-

-

-

up to 213

  Mono Lobe ignimbrite 

.

77

3.6- 4.5

-

-

-

up to 660

  Plinian

Dunbar & Hervig (1992b)

77

3.5- 6.0

0.05

0.07

-

-

  ignimbrites

.

77

2.0- 4.0

0.05

0.07

-

-

  Plinian

Wallace et al. (1994)

77

6.0±0.4

-

-

-

60±40

  Early Ignimbrite

"

77

6.5±0.3

-

-

-

120±60

  Mono Lobe ignimbrite

"

77

4.6±0.4

-

-

-

150-1100

Juniper Mtn. Volcanic

.

.

.

.

.

.

.

Center, ID, USA

Manley (1994)

75

.

.

.

.

.

  Badlands (lava)

"

77

1.4- 3.8

0.09-0.23

0.06-0.11

-

-

  Badlands (sub-Plinian)

"

76

1.7- 3.6

0.12-0.17

0.08-0.13

-

-

  Carter Spring (lava)

"

77

1.4-3.1

0.14-0.51

0.08-0.13

-

-

  " " (fountain-fed)

"

.

0.6-2.1

0.12-0.21

-

-

-

Peralkaline Rhyolites

.

.

.

.

.

.

.

  Pantelleria, Italy

Lowenstern & Mahood ('91)

70*

1.4- 2.1

-

~0.9

-

<100

  Pantelleria, Italy

Kovalenko et al. (1994)

69-70*

up to 4.3%

0.10-0.26

0.60-1.20

-

-

  Fantale, Ethiopia

Webster et al. (1993)

71*

4.6- 4.9

0.30

0.30

-

-

  Olkaria, Kenya

Wilding et al. (1993)

70*

0.3- 3

-

-

-

-

Note: Data presented as X000-Y000 indicates range of values in original publication. Data presented with '±' shows 1s as listed in original publication. Dash indicates data not reported.
# CO2 by IR spectroscopy (FTIR). In studies with CO2 data, H2O data are also by FTIR.
ÝPersonal communication (1994).
*Peralkaline rocks: Molar (Na2O+K2O)/Al2O3 >> 1.0

Though not all silicic melts have been shown to contain high H2O concentrations, most seem to have at least 4 wt.% dissolved H2O in the melt. Some magmas are zoned in H2O before eruption (Bishop and Bandelier tuffs), whereas others are homogeneous (1912 Valley of 10,000 Smokes rhyolite, Taupo). Carbon dioxide has been detected in several systems (Pine Grove, Bishop tuff, Pinatubo), though others contain virtually none (Crater Lake, 1912 Valley of 10,000 Smokes rhyolite). Chlorine and F are highly variable in concentration, and their abundances appear to be correlated with tectonic setting (higher Cl/F in arcs relative to continental settings). Sulfur is generally very low (<100 ppm) in high-silica rhyolitic melts with < 1.0 wt.% FeO, although there is experimental evidence that oxidized, high-temperature silicic melts can contain higher concentrations of S as dissolved sulfate (Luhr 1990). Table 3 summarizes current understanding of volatile concentrations in silicic melts, based on analyses of silicate MI.

Table 3. Summary of recent studies of volatile concentrations and saturation pressures in unleaked MI from high-silica rhyolites.

Volatile Species

Typical Concentrations

Additional Information

H2O

Rarely <3% and rarely > 7%

Lower concentrations common in leaked MI

CO2

Up to 1000 ppm, though some systems contain very little (<25 ppm)

Concentration highly dependent on degree of pre-entrapment degassing

Cl

600 ppm to 2700 ppm

Peralkaline rhyolitic and some mafic MI contain > 3000 ppm

F

400 ppm to 1500 ppm

Continental systems may contain much higher concentrations: > 1 wt.%

S

Usually < 200 ppm; often <60 ppm

Concentrations are much higher in andesites and basalts

Saturation Pressure

Generally between 1 and 4 kbar

 

Calculated as minimum pressure at which MI was trapped, given H2O and CO2 concentrations.

Data on magmatic volatiles have the following applications. 1) They provide constraints on the amounts of magma-derived volatiles likely in ore-forming systems and on the general compositions of exsolving fluids. 2) They can demonstrate the relative importance of decompression-related degassing versus crystallization-induced degassing on the fluid-release history of a magma (Lowenstern 1994b). For example, if a magma is shown to have been volatile saturated at a given depth, the mass of exsolved fluid produced during further ascent can be calculated (Shinohara & Kazahaya 1995). 3) They give reliable estimates of the dissolved concentrations of ore-metals in magmas prior to degassing. Prior to the study of MI, economic geologists had to depend solely on analyses of degassed intrusions and extrusive rocks to characterize the metal and volatile composition of potential ore-forming magmas. 4) They may be used as geobarometers to determine the minimum pressures at which crystals grew (Anderson et al. 1989; Lowenstern 1994b).

Care must be used when interpreting data from MI, as they represent only a single phase within the magma reservoir: the melt phase. To estimate the total amount of volatiles in a magma reservoir, one must have constraints on the relative amount of melt, crystals and exsolved fluid (Gerlach et al., accepted; Wallace et al. 1994). Though MI yield constraints on the composition of fluids in equilibrium with the magma, one must also recognize that the composition of exsolved fluid may change as it ascends from the magma, cools and interacts with the surrounding environment (Hedenquist 1995).

Volcano Hazards Program | U.S. Geological Survey Skip to main content
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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.

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News

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

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

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

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

Volcano Watch — What do small earthquakes beneath Kīlauea summit mean for the ongoing eruption?

Volcano Watch — What do small earthquakes beneath Kīlauea summit mean for the ongoing eruption?

View All

Publications

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

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
By
Volcano Hazards Program, Volcano Science Center

Luminescence dating of hydrothermal explosions in the Yellowstone Plateau volcanic field Luminescence dating of hydrothermal explosions in the Yellowstone Plateau volcanic field

Hydrothermal explosions are a significant geological hazard in some active volcanic systems; however, the timing and triggering mechanisms of these explosions are poorly constrained. This study applies luminescence dating techniques to hydrothermal explosion deposits in the Yellowstone Plateau volcanic field to constrain explosion chronologies and evaluate potential triggering mechanisms...
Authors
Karissa Cordero, Nathan Brown, Lauren N. Harrison, Shaul Hurwitz
By
Volcano Hazards Program, Volcano Science Center
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