The assignment of official hazard alert levels is the responsibility of national or regional volcano observatories under the umbrella of the World Organization of Volcano Observatories (WOVO). The following discussion of volcanic hazard alert levels is adapted from the WOVO website, with permission.
In a volcanic crisis, there is often worldwide interest in the volcano's hazard alert levels. With the exception of color codes for aviation, though, there is currently no standardized international volcano alert levels system. This is due to: (a) wide variation in the behavior of individual volcanoes and in monitoring capabilities, and (b) the different needs of populations, including different languages and symbolism of colors used. National volcano observatories have developed alert level protocols that are regionally variable and differ significantly in detail. The WOVO site contains links to the regional volcano observatories and the alert systems they utilize.
Organizations with interest in natural hazards are strongly cautioned against posting global volcano hazard alerts or eruption "forecasts" that do not originate from volcano observatories or regional agencies with both responsibility for and familiarity with those volcanoes. Posting of hazard alert levels can have major public safety and economic implications, and should not be done lightly. The data needed to provide alert levels come from onsite and remote monitoring instrumentation and are best evaluated by staff of regional volcano observatories who are the most familiar with activity at their volcanoes. The responsible observatories and organizations are listed on the WOVO website, and readers are directed to these organizations for information on current volcano alert levels.
Currently, there is no WOVO-endorsed source of worldwide Volcanic Alert Levels, with the exception of aviation color codes. For those seeking a near real-time overview of current reported activity that incorporates direct observatory sources WOVO recommends the Weekly Activity Reports compiled by the Smithsonian Institution’s Global Volcanism Program (GVP) and the U.S. Geological Survey.
Many instances of aircraft flying into volcanic ash clouds have demonstrated the life-threatening and costly damages that can be sustained. Consequently, a universal volcanic alert level system for aviation has been developed (as part of the International Airways Volcano Watch, a universal warning system coordinated by the International Civil Aviation Organization, a UN specialist agency). This system uses four color codes, designed to help pilots, dispatchers, and air-traffic controllers quickly find the status of numerous volcanoes that might endanger aircraft.
The color codes reflect conditions at or near a volcano and are not intended to indicate hazards posed downwind by drifting ash - all discernible ash clouds are assumed to be highly hazardous and to be avoided. Furthermore, the aviation color code should not be extrapolated to represent hazards posed on the ground, which might be quite different.
Not all observatories currently provide information in this format, but where they do, the aviation color code is currently defined as below.
AVIATION COLOR CODES RECOMMENDED BY THE INTERNATIONAL CIVIL AVIATION ORGANIZATION |
|
GREEN |
Volcano is in normal, non-eruptive state. or, after a change from a higher level: Volcanic activity considered to have ceased, and volcano reverted to its normal, non-eruptive state. |
YELLOW |
Volcano is experiencing signs of elevated unrest above known background levels. or, after a change from higher level: Volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase. |
ORANGE |
Volcano is exhibiting heightened unrest with increased likelihood of eruption. or, Volcanic eruption is underway with no or minor ash emission. [specify ash-plume height if possible] |
RED |
Eruption 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] |