Page "Volcano warning schemes of the United States" Paragraph 2

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.