Alert Level

Criteria

Interpretation

0

Background, quiet

No eruption in foreseeable future.

1

Low level seismicity, fumarolic, ground deformation and other parameters.

Magmatic, tectonic or hydrothermal disturbance; no eruption imminent.

2

Low to moderate level of seismicity, persistence of local earthquakes. Ground deformation measurements above baseline levels. Increased water and/or ground probe hole temperatures, increased bubbling at Main Crater Lake. Increased acidity and volcanic gas flux in the Main Crater lake.

A) Probable magmatic intrusion; could eventually lead to an eruption.

B) If trend declines, volcano may soon go to level 1

3

Relatively high unrest manifested by seismic swarms including the occurrence of low frequency earthquakes and/or volcanic tremor (some events felt). Sudden or increasing changes in temperature or bubbling activity or volcanic gas emission or crater lake acidity. Bulging of the edifice and fissuring may accompany seismicity.

Eruption is imminent.

A) If trend is one of increasing unrest, eruption is possible within days to a few weeks.

B) If trend is one of decreasing unrest, volcano may soon go to level 2

4

Intense unrest, continuing seismic swarms, including harmonic tremor and other “low frequency earthquakes,” that are usually felt, profuse steaming along existing and new vents and fissures. Extreme ground deformation and fissuring, lava fountaining or lava flows, may occur.

Hazardous explosive eruption is possible within days.

5

Explosive eruption column, may be accompanied by base surges or volcanic tsunami; activity accompanied by explosion earthquakes, felt volcano-tectonic earthquakes and intense volcanic tremor.

Hazardous eruption in progress. Extreme hazards to communities on Volcano Island and lakeshore towns and ashfalls on downwind sectors.