Volcano warning schemes

USGS Volcano Warning Scheme for the United States

The United States Geological Survey (USGS) has adopted a common system nationwide for characterizing the level of unrest and eruptive activity at volcanoes. The new volcano alert-level system is now used by the Alaska Volcano Observatory, the Cascades Volcano Observatory, the Hawaiian Volcano Observatory, the Long Valley Observatory, and the Yellowstone Volcano Observatory.

Under the new 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 a minor eruption underway that poses limited hazards; and, "Warning", if a highly hazardous eruption is underway or imminent (Table 1). 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.

Summary of Volcanic-Alert Levels

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.

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.

Warning system for Cascade Range volcanoes in Washington and Oregon

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

References

* [http://volcanoes.usgs.gov/Products/Warn/WarnSchemes.html Volcano Hazard Program warning scheme page]
* [http://www.avo.alaska.edu/activity/avoreport.php?view=info&id=488&type=info&month=September&year=2006 AVO information release about new warning scheme]