Ground terms
USGS uses one nationwide system to characterize conditions at U.S. volcanoes: quiet, unrest, or eruption. Notices come from the regional volcano observatories. A Volcano Activity Notice is issued when the ground alert level changes. The ground terms, in the sense of that page, are:
| Term | Meaning for people on the ground |
|---|---|
| Normal | Typical background, noneruptive state, or a return to that state after a higher level. |
| Advisory | Elevated unrest above the known background, or activity that has decreased from a higher level and is still being watched. |
| Watch | Heightened or escalating unrest with increased potential of eruption, timeframe uncertain, or an eruption underway that poses limited hazards. |
| Warning | A hazardous eruption is imminent, underway, or suspected. |
| Unassigned | Not enough information to assess the volcano’s status. |
Watch includes the phrase “timeframe uncertain.” That is USGS saying the level is not a date. Warning means a hazardous eruption is imminent, underway, or suspected. It is still an observatory notice about a volcano that is already in that state, not a prediction issued by this website.
Aviation colors are a second scale
The same USGS page has ranked colors for airborne ash, separate from the ground terms. A Volcano Notice for Aviation is issued when the aviation color code changes. The color definitions live on that USGS page. This site does not show the current color or the current ground term for any volcano.
What you will not find in the catalog
The Smithsonian snapshot behind the volcano map has a last-eruption year and an evidence code. Those fields are not Normal, Advisory, Watch, or Warning. The preparedness page is about following an official notice and an evacuation order. The VEI page compares eruptions that have already been sized. None of the three is a live alert level.