Volcano warning schemes of the United States

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In October 2006, the United States Geological Survey (USGS) adopted a nationwide alert system for characterizing the level of unrest and eruptive activity at volcanoes. The system is now used by the Alaska Volcano Observatory, the California Volcano Observatory (California and Nevada), the Cascades Volcano Observatory (Washington, Oregon and Idaho), the Hawaiian Volcano Observatory and the Yellowstone Volcano Observatory (Montana, Wyoming, Colorado, Utah, New Mexico and Arizona).

United States Geological Survey Scientific agency of the United States government

The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology, geography, geology, and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility.

Alaska Volcano Observatory

The Alaska Volcano Observatory (AVO) is a joint program of the United States Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). AVO was formed in 1988, and uses federal, state, and university resources to monitor and study Alaska's volcanology, hazardous volcanoes, to predict and record eruptive activity, and to mitigate volcanic hazards to life and property. The Observatory website allows users to monitor active volcanoes, with seismographs and webcameras that update regularly. AVO now monitors more than 20 volcanoes in Cook Inlet, which is close to Alaskan population centers, and the Aleutian Arc due to the hazard that plumes of ash pose to aviation.

California Volcano Observatory volcano observatory in Eastern California

The California Volcano Observatory (CalVO) is the volcano observatory that monitors the volcanic and geologic activity of California and Nevada. It is a part of the Volcano Hazards Program of the United States Geological Survey, a scientific agency of the United States government.

Contents

Under this system, the USGS ranks the level of activity at a U.S. volcano using the terms "normal", for typical volcanic activity in a non-eruptive phase; "advisory", for elevated unrest; "watch", for escalating unrest or an eruption underway that poses limited hazards; and, "warning", if a highly hazardous eruption is underway or imminent. These levels reflect conditions at a volcano and the expected or ongoing hazardous volcanic phenomena. When an alert level is assigned by an observatory, accompanying text will give a fuller explanation of the observed phenomena and clarify hazard implications to affected groups.

Both ground and aviation alerts are provided for volcanoes in the U.S. Volcanic-alert icons.jpg
Both ground and aviation alerts are provided for volcanoes in the U.S.

Summary of Volcanic Activity Alert Notification System

NormalTypical background activity of a volcano in a non-eruptive state
  • After a change from a higher level: Volcanic activity considered to have ceased, and volcano reverted to its normal, non-eruptive state.
AdvisoryElevated unrest above known background activity
  • After a change from a higher level: Volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
WatchHeightened/escalating unrest with increased potential for eruptive activity (timeframe variable) OR a minor eruption underway that poses limited hazards.
WarningHighly hazardous eruption underway or imminent.

Aviation color codes

CodeDescription
GreenVolcano is in its normal "dormant" state
  • After a change from a higher level: Volcanic activity considered to have ceased, and volcano reverted to its normal, non-eruptive state.
YellowVolcano is exhibiting signs of elevated unrest above known background levels.
  • After a change from a higher level: Volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
OrangeVolcano is exhibiting heightened unrest with increased likelihood of eruption,
or,
Volcanic eruption underway with no or minor ash emission (specify ash-plume height if possible).
RedEruption is forecast to be imminent with significant emission of ash into the atmosphere likely,
or,
Eruption is underway with significant emission of ash into the atmosphere (specify ash-plume height if possible).

Earlier volcano warning schemes for the United States

Prior to October 2006, three parallel Volcano warning schemes were used by the United States Geological Survey and the volcano observatories for different volcano ranges in the United States. They each have a base level for dormant-quiescent states and three grades of alert.

Volcano A rupture in the crust of a planetary-mass object that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface

A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

Color Code Conditions, Long Valley Caldera and Mono-Inyo Craters Region, California

Developed in 1997 to replace a previous 5-level system devised in 1991.

CodeNarrativeLevels
GreenNo immediate riskLevels from Quiescent to Strong Unrest
YellowWatchIntense Unrest
OrangeWarningAccelerating intense unrest: eruption likely within hours to days
RedEruption in progressLevels 1 (Minor eruption) to 4 (Massive explosive eruption)

Level of Concern Color Codes for volcanoes in Alaska

The Alaska Volcano Observatory (AVO) used the following color-coded system to rate volcanic activity. It was originally established during the 1989-90 eruption of Redoubt Volcano.

ClassDescription
GreenVolcano is in its normal "dormant" state.
YellowVolcano is restless. Seismic activity is elevated. Potential for eruptive activity is increased.
OrangeSmall ash eruption expected or confirmed. Plume(s) not likely to rise above 25,000 feet above sea level.
RedLarge ash eruptions expected or confirmed. Plume likely to rise above 25,000 feet above sea level.

All five classifications are spelled as proper nouns, i.e., Level of Concern Color Code Orange not Level of concern color code Orange or any other variation. On its website the AVO spells the alert color in all capitals, but this is not otherwise necessary outside their system.

A proper noun is a noun directly associated with an entity and primarily used to refer to that entity, such as London, Jupiter, Sharon, or Microsoft, as distinguished from a common noun, which is a noun directly associated with a class of entities and primarily used to refer to instances of a specific class.

Warning system for Cascade Range volcanoes in Washington and Oregon

Introduced following the May 18, 1980, eruption of Mount St. Helens.

Mount St. Helens US American volcano

Mount St. Helens is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It is 50 miles (80 km) northeast of Portland, Oregon and 96 miles (154 km) south of Seattle, Washington. Mount St. Helens takes its English name from the British diplomat Lord St Helens, a friend of explorer George Vancouver who made a survey of the area in the late 18th century. The volcano is located in the Cascade Range and is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire that includes over 160 active volcanoes. This volcano is well known for its ash explosions and pyroclastic flows.

CodeNarrativeLevels
No Alert"Information Statements" may be issued about unusual but non-threatening events
Alert Level OneNotice of Volcanic UnrestSignificant anomalous conditions are recognized that could be indicative of an eventual hazardous volcanic event.
Alert Level TwoVolcano AdvisoryMonitoring and evaluation indicate that processes are underway that have significant likelihood of culminating in hazardous volcanic activity but when the evidence does not indicate that a life- or property-threatening event is imminent.
Alert Level ThreeVolcano AlertMonitoring and evaluation indicate that precursory events have escalated to the point where a volcanic event with attendant volcanologic or hydrologic hazards threatening to life and property appears imminent or is underway.

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Mount Redoubt Volcanic cone in the United States

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The National Volcano Early Warning and Monitoring System is a U.S. federal program within the U.S. Geological Survey for monitoring volcano activity and providing early warning to threatened areas. It was authorized by the John D. Dingell, Jr. Conservation, Management, and Recreation Act on March 12, 2019.

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