GREEN: Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
NORMAL: Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.More information on color/alert definitions
AVO Shishaldin GREEN/NORMAL - Prolonged data outage resolved. Aviation Color Code assigned at GREEN and Volcano Alert Level at NORMAL. Complete report text
Mathematical models developed by the USGS forecast various aspects of how a volcanic ash plume will interact with wind—where, how high, and how fast ash particles will be transported in the atmosphere, as well as where ash will fall out and accumulate on the ground. AVO runs these models when a volcano is restless by assuming a reasonable hypothetical eruption, to provide a pre-eruptive forecast of areas likely to be affected. During an ongoing eruption, AVO will update the forecast with actual observations (eruption start time and duration, plume height) as they become available. Click on individual graphics to learn more.