|
Alert Level |
Criteria |
Interpretation |
|
No Alert |
Background, quiet |
No eruption in foreseeable
future |
|
1 |
Low level seismic, fumarolic,
other unrest |
Magmatic, tectonic, or
hydrothermal disturbance; no eruption imminent |
|
2 |
Moderate level of seismic,
other unrest with positive evidence for involvement of magma |
Probable magma intrusion; could
eventually lead to an eruption |
|
3 |
Relatively high and increasing
unrest, including numerous low frequency volcanic earthquakes,
accelerating ground deformation, increasing fumarolic
activity. |
Increasing likelihood of an
eruption, possibly explosive, probably within days to weeks. |
|
4 |
Intense unrest, including
harmonic tremor and/or many "long-period" (i.e., low
frequency) earthquakes and/or dome growth and/or small
explosions |
Magma close to or at the
earth’s surface. Hazardous explosive eruption likely, possibly
within hours or days. |
|
5 |
Hazardous eruption in progress.
Hazards in valleys and downwind. |
|
