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Most volcanoes provide warnings before an eruption. Magmatic eruptions involve the rise of magma toward the surface, which normally generates detectable earthquakes. It can also deform the ground surface and cause anomalous heat flow or changes in the temperature and chemistry of the groundwater and spring waters. Steam-blast eruptions, however, can occur with little or no warning as superheated water flashes to steam.
Notable precursors to an eruption might include:
These precursors do not indicate the type or scale of an expected eruption (that information is best obtained by mapping previous eruptions). Precursors can continue for weeks, months, or even years before eruptive activity begins, or they can subside at any time and not be followed by an eruption. Italy’s Campi Flegrei volcano has been showing signs of unrest for over 60 years.
Learn more:
Instruments to measure sulfur dioxide and carbon dioxide can be mounted in aircraft to determine the quantity of gas being emitted on a daily basis. Such instruments can also be used in a ground-based mode. An instrument that detects carbon dioxide can be installed on a volcano and configured to send data continuously via radio to an observatory. Sulfur dioxide in volcanic clouds can also be...
Volcanoes are inherently beautiful places where forces of nature combine to produce awesome events and spectacular landscapes. For volcanologists, they're FUN to work on! Safety is, however, always the primary concern because volcanoes can be dangerous places. USGS scientists try hard to understand the risk inherent in any situation, then train and equip themselves with the tools and support...
Hot lava samples provide important information about what's going on in a volcano's magma chambers. We know from laboratory experiments that the more magnesium there is in magma, the hotter it is. Chemical analysis, therefore, provides the means not only to determine the crystallization history of lava but also to establish the temperature at which it was erupted. For example, Kilauea's 1997 lavas...
There are 161 potentially active volcanoes in the United States. According to a 2018 USGS assessment, 57 volcanoes are a high threat or very high threat to public safety. Many of these volcanoes have erupted in the recent past and will erupt again in the foreseeable future. As populations increase, areas near volcanoes are being developed and aviation routes are increasing. As a result, more...
Sometimes, yes. A few large regional earthquakes (greater than magnitude 6) are considered to be related to a subsequent eruption or to some type of unrest at a nearby volcano. However, volcanoes can only be triggered into eruption by nearby tectonic earthquakes if they are already poised to erupt. This requires two conditions to be met: Enough "eruptible" magma within the volcanic system...
Not usually. Earthquakes associated with eruptions rarely exceed magnitude 5, and these moderate earthquakes are not big enough to destroy buildings and roads. The largest earthquakes at Mount St. Helens in 1980 were magnitude 5, large enough to sway trees and damage buildings, but not destroy them. During the huge eruption of Mount Pinatubo in the Philippines in 1991, dozens of light to moderate...
There is no definitive evidence that an eruption at one volcano can trigger an eruption at a volcano that’s hundreds of kilometers/miles away or on a different continent. There are a few historic examples of simultaneous eruptions from volcanoes (or volcanic vents) located within about 10 kilometers (6 miles) of each other, but it's difficult to determine whether one eruption caused the other...
Excluding steam eruptions, these volcanoes have shown activity: Mount St. Helens, Washington - Eruptions and/or lava dome growth occurred in the late 1700s, 1800-1857, 1980-1986, and 2004-2008. Lassen Peak, California - A series of steam blasts began on May 30, 1914. An eruption occurred 12 months later on May 21, 1915. Minor activity continued through the middle of 1917. Mount Hood, Oregon -...
Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma. Since it is lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually, some of the magma pushes through vents and fissures to the Earth's surface. Magma that has erupted is called lava. Some volcanic eruptions are explosive and others are not. The...
There are some very large, ancient, ‘inactive’ sinkholes in some areas of the U.S. that are thousands of years old. Alabama claims to have the largest recent collapse sinkhole. It is called the “Golly Hole” and is located in Shelby County in the central part of the state. It collapsed suddenly in 1972. The sinkhole is about 325 feet long, 300 feet wide, and 120 feet deep. Learn more: USGS Water...
Over geologic time, volcanic eruptions and related processes have directly and indirectly benefited mankind: Volcanic materials ultimately break down and weather to form some of the most fertile soils on Earth, cultivation of which has produced abundant food and fostered civilizations. The internal heat associated with young volcanic systems has been harnessed to produce geothermal energy. Most of...
View of episode 9 lava fountaining in Halema‘uma‘u at the summit of Kīlauea the evening of February 11, 2025. Lava fountain heights were decreased from the morning of February 11, when episode 9 began. At approximately 8:15 p.m.
View of episode 9 lava fountaining in Halema‘uma‘u at the summit of Kīlauea the evening of February 11, 2025. Lava fountain heights were decreased from the morning of February 11, when episode 9 began. At approximately 8:15 p.m.
USGS scientist Alex Iezzi atop Santa Maria overlooking an eruption of the Santiaguito lava-dome complex, Guatemala.
USGS scientist Alex Iezzi atop Santa Maria overlooking an eruption of the Santiaguito lava-dome complex, Guatemala.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor is one of five sensors on board NASA's Terra satellite. ASTER data and imagery are crucial tools for monitoring volcanoes for any clues of imminent eruptions, for studying volcanoes during an eruption, and for analyzing impacts after an eruption.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor is one of five sensors on board NASA's Terra satellite. ASTER data and imagery are crucial tools for monitoring volcanoes for any clues of imminent eruptions, for studying volcanoes during an eruption, and for analyzing impacts after an eruption.
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
Photogrammetry is the science of making precise measurements by the use of photography. USGS geologist Angie Diefenbach describes how she uses a digital camera and computer software to understand the growth rate of lava domes during a volcanic eruption.
Photogrammetry is the science of making precise measurements by the use of photography. USGS geologist Angie Diefenbach describes how she uses a digital camera and computer software to understand the growth rate of lava domes during a volcanic eruption.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
USGS volcano seismologist, Seth Moran, describes how seismology and seismic networks are used to mitigate volcanic hazards.
USGS volcano seismologist, Seth Moran, describes how seismology and seismic networks are used to mitigate volcanic hazards.
USGS technologist Rick LaHusen describes how the development and deployment of instruments plays a crucial role in mitigating volcanic hazards.
USGS technologist Rick LaHusen describes how the development and deployment of instruments plays a crucial role in mitigating volcanic hazards.
Volcanic ash is geographically the most widespread of all volcanic hazards. USGS geologist Larry Mastin describes how volcanic ash can disrupt lives many thousands of miles from an erupting volcano. The development of ash cloud models and ash cloud disruption to air traffic is highlighted.
Volcanic ash is geographically the most widespread of all volcanic hazards. USGS geologist Larry Mastin describes how volcanic ash can disrupt lives many thousands of miles from an erupting volcano. The development of ash cloud models and ash cloud disruption to air traffic is highlighted.
--fissures...fountains...and flows
by Matthew Patrick, USGS, Hawaiian Volcano Observatory
--fissures...fountains...and flows
by Matthew Patrick, USGS, Hawaiian Volcano Observatory
The May 18, 1980 eruption of Mount St. Helens triggered a growth in volcano science and volcano monitoring. Five USGS volcano observatories have been established since the eruption. With new technologies and improved awareness of volcanic hazards USGS scientists are helping save lives and property across the planet.
The May 18, 1980 eruption of Mount St. Helens triggered a growth in volcano science and volcano monitoring. Five USGS volcano observatories have been established since the eruption. With new technologies and improved awareness of volcanic hazards USGS scientists are helping save lives and property across the planet.
USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens. Loss of their colleague David A. Johnston and 56 others in the eruption cast a pall over one of the most dramatic geologic moments in American history.
USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens. Loss of their colleague David A. Johnston and 56 others in the eruption cast a pall over one of the most dramatic geologic moments in American history.
USGS Scientist-in-Charge of Yellowstone Volcano Observatory, Jake Lowenstern, answers the following questions to provide a tour of the Yellowstone Volcano Observatory: "What is YVO?", "How do you monitor volcanic activity at Yellowstone?", "How are satellites used to study deformation?", "Do you monitor geysers or any other aspect of the Park?", "Are earthquakes and
USGS Scientist-in-Charge of Yellowstone Volcano Observatory, Jake Lowenstern, answers the following questions to provide a tour of the Yellowstone Volcano Observatory: "What is YVO?", "How do you monitor volcanic activity at Yellowstone?", "How are satellites used to study deformation?", "Do you monitor geysers or any other aspect of the Park?", "Are earthquakes and
Mount St. Helens reawakened in late September 2004. Small magnitude earthquakes beneath the 1980-1986 lava dome increased in frequency and size, and a growing welt formed on the southeast margin of the previous lava dome and nearby portions of Crater Glacier.
Mount St. Helens reawakened in late September 2004. Small magnitude earthquakes beneath the 1980-1986 lava dome increased in frequency and size, and a growing welt formed on the southeast margin of the previous lava dome and nearby portions of Crater Glacier.
A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during a FLIR/maintenance flight on January 24, 2006.
A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during a FLIR/maintenance flight on January 24, 2006.
Augustine volcano viewed from the west.
Augustine volcano viewed from the west.
Instruments to measure sulfur dioxide and carbon dioxide can be mounted in aircraft to determine the quantity of gas being emitted on a daily basis. Such instruments can also be used in a ground-based mode. An instrument that detects carbon dioxide can be installed on a volcano and configured to send data continuously via radio to an observatory. Sulfur dioxide in volcanic clouds can also be...
Volcanoes are inherently beautiful places where forces of nature combine to produce awesome events and spectacular landscapes. For volcanologists, they're FUN to work on! Safety is, however, always the primary concern because volcanoes can be dangerous places. USGS scientists try hard to understand the risk inherent in any situation, then train and equip themselves with the tools and support...
Hot lava samples provide important information about what's going on in a volcano's magma chambers. We know from laboratory experiments that the more magnesium there is in magma, the hotter it is. Chemical analysis, therefore, provides the means not only to determine the crystallization history of lava but also to establish the temperature at which it was erupted. For example, Kilauea's 1997 lavas...
There are 161 potentially active volcanoes in the United States. According to a 2018 USGS assessment, 57 volcanoes are a high threat or very high threat to public safety. Many of these volcanoes have erupted in the recent past and will erupt again in the foreseeable future. As populations increase, areas near volcanoes are being developed and aviation routes are increasing. As a result, more...
Sometimes, yes. A few large regional earthquakes (greater than magnitude 6) are considered to be related to a subsequent eruption or to some type of unrest at a nearby volcano. However, volcanoes can only be triggered into eruption by nearby tectonic earthquakes if they are already poised to erupt. This requires two conditions to be met: Enough "eruptible" magma within the volcanic system...
Not usually. Earthquakes associated with eruptions rarely exceed magnitude 5, and these moderate earthquakes are not big enough to destroy buildings and roads. The largest earthquakes at Mount St. Helens in 1980 were magnitude 5, large enough to sway trees and damage buildings, but not destroy them. During the huge eruption of Mount Pinatubo in the Philippines in 1991, dozens of light to moderate...
There is no definitive evidence that an eruption at one volcano can trigger an eruption at a volcano that’s hundreds of kilometers/miles away or on a different continent. There are a few historic examples of simultaneous eruptions from volcanoes (or volcanic vents) located within about 10 kilometers (6 miles) of each other, but it's difficult to determine whether one eruption caused the other...
Excluding steam eruptions, these volcanoes have shown activity: Mount St. Helens, Washington - Eruptions and/or lava dome growth occurred in the late 1700s, 1800-1857, 1980-1986, and 2004-2008. Lassen Peak, California - A series of steam blasts began on May 30, 1914. An eruption occurred 12 months later on May 21, 1915. Minor activity continued through the middle of 1917. Mount Hood, Oregon -...
Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma. Since it is lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually, some of the magma pushes through vents and fissures to the Earth's surface. Magma that has erupted is called lava. Some volcanic eruptions are explosive and others are not. The...
There are some very large, ancient, ‘inactive’ sinkholes in some areas of the U.S. that are thousands of years old. Alabama claims to have the largest recent collapse sinkhole. It is called the “Golly Hole” and is located in Shelby County in the central part of the state. It collapsed suddenly in 1972. The sinkhole is about 325 feet long, 300 feet wide, and 120 feet deep. Learn more: USGS Water...
Over geologic time, volcanic eruptions and related processes have directly and indirectly benefited mankind: Volcanic materials ultimately break down and weather to form some of the most fertile soils on Earth, cultivation of which has produced abundant food and fostered civilizations. The internal heat associated with young volcanic systems has been harnessed to produce geothermal energy. Most of...
View of episode 9 lava fountaining in Halema‘uma‘u at the summit of Kīlauea the evening of February 11, 2025. Lava fountain heights were decreased from the morning of February 11, when episode 9 began. At approximately 8:15 p.m.
View of episode 9 lava fountaining in Halema‘uma‘u at the summit of Kīlauea the evening of February 11, 2025. Lava fountain heights were decreased from the morning of February 11, when episode 9 began. At approximately 8:15 p.m.
USGS scientist Alex Iezzi atop Santa Maria overlooking an eruption of the Santiaguito lava-dome complex, Guatemala.
USGS scientist Alex Iezzi atop Santa Maria overlooking an eruption of the Santiaguito lava-dome complex, Guatemala.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor is one of five sensors on board NASA's Terra satellite. ASTER data and imagery are crucial tools for monitoring volcanoes for any clues of imminent eruptions, for studying volcanoes during an eruption, and for analyzing impacts after an eruption.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor is one of five sensors on board NASA's Terra satellite. ASTER data and imagery are crucial tools for monitoring volcanoes for any clues of imminent eruptions, for studying volcanoes during an eruption, and for analyzing impacts after an eruption.
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
Photogrammetry is the science of making precise measurements by the use of photography. USGS geologist Angie Diefenbach describes how she uses a digital camera and computer software to understand the growth rate of lava domes during a volcanic eruption.
Photogrammetry is the science of making precise measurements by the use of photography. USGS geologist Angie Diefenbach describes how she uses a digital camera and computer software to understand the growth rate of lava domes during a volcanic eruption.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
USGS volcano seismologist, Seth Moran, describes how seismology and seismic networks are used to mitigate volcanic hazards.
USGS volcano seismologist, Seth Moran, describes how seismology and seismic networks are used to mitigate volcanic hazards.
USGS technologist Rick LaHusen describes how the development and deployment of instruments plays a crucial role in mitigating volcanic hazards.
USGS technologist Rick LaHusen describes how the development and deployment of instruments plays a crucial role in mitigating volcanic hazards.
Volcanic ash is geographically the most widespread of all volcanic hazards. USGS geologist Larry Mastin describes how volcanic ash can disrupt lives many thousands of miles from an erupting volcano. The development of ash cloud models and ash cloud disruption to air traffic is highlighted.
Volcanic ash is geographically the most widespread of all volcanic hazards. USGS geologist Larry Mastin describes how volcanic ash can disrupt lives many thousands of miles from an erupting volcano. The development of ash cloud models and ash cloud disruption to air traffic is highlighted.
--fissures...fountains...and flows
by Matthew Patrick, USGS, Hawaiian Volcano Observatory
--fissures...fountains...and flows
by Matthew Patrick, USGS, Hawaiian Volcano Observatory
The May 18, 1980 eruption of Mount St. Helens triggered a growth in volcano science and volcano monitoring. Five USGS volcano observatories have been established since the eruption. With new technologies and improved awareness of volcanic hazards USGS scientists are helping save lives and property across the planet.
The May 18, 1980 eruption of Mount St. Helens triggered a growth in volcano science and volcano monitoring. Five USGS volcano observatories have been established since the eruption. With new technologies and improved awareness of volcanic hazards USGS scientists are helping save lives and property across the planet.
USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens. Loss of their colleague David A. Johnston and 56 others in the eruption cast a pall over one of the most dramatic geologic moments in American history.
USGS scientists recount their experiences before, during and after the May 18, 1980 eruption of Mount St. Helens. Loss of their colleague David A. Johnston and 56 others in the eruption cast a pall over one of the most dramatic geologic moments in American history.
USGS Scientist-in-Charge of Yellowstone Volcano Observatory, Jake Lowenstern, answers the following questions to provide a tour of the Yellowstone Volcano Observatory: "What is YVO?", "How do you monitor volcanic activity at Yellowstone?", "How are satellites used to study deformation?", "Do you monitor geysers or any other aspect of the Park?", "Are earthquakes and
USGS Scientist-in-Charge of Yellowstone Volcano Observatory, Jake Lowenstern, answers the following questions to provide a tour of the Yellowstone Volcano Observatory: "What is YVO?", "How do you monitor volcanic activity at Yellowstone?", "How are satellites used to study deformation?", "Do you monitor geysers or any other aspect of the Park?", "Are earthquakes and
Mount St. Helens reawakened in late September 2004. Small magnitude earthquakes beneath the 1980-1986 lava dome increased in frequency and size, and a growing welt formed on the southeast margin of the previous lava dome and nearby portions of Crater Glacier.
Mount St. Helens reawakened in late September 2004. Small magnitude earthquakes beneath the 1980-1986 lava dome increased in frequency and size, and a growing welt formed on the southeast margin of the previous lava dome and nearby portions of Crater Glacier.
A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during a FLIR/maintenance flight on January 24, 2006.
A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during a FLIR/maintenance flight on January 24, 2006.
Augustine volcano viewed from the west.
Augustine volcano viewed from the west.