Compare volcanoes
Choose two to four US-monitored volcanoes that USGS currently lists at an elevated alert level and see what USGS reports for each, side by side.
Last successful collection 2026-10-23 14:04 UTC · Source: USGS Hazard Notification System (HANS)
Categories, not measurements. A colour code or alert level is a USGS category. It is not a number, and it does not measure how large an eruption is or how much risk a volcano poses.
US-monitored volcanoes only, elevated only. Volcanoes at a normal level and volcanoes outside US monitoring are not listed. This is not an emergency alert service.
1. Choose 2 to 4 volcanoes
2 of 4 selected.
2. Compare
They are at different aviation colour codes (Great Sitkin ORANGE, Ahyi Seamount YELLOW). The codes are ordered categories, not measurements of eruption size or risk.
Great Sitkin
- Green
- Yellow
- Orange (this volcano)
- Red
- Aviation colour codeDiffers
- ORANGE
- Ground alert levelDiffers
- WATCH
- Monitored byDiffers
- Alaska Volcano Observatory
- Coordinates (USGS registry)
- 52.08° N, 176.11° W
- Latest USGS notice
- 2026-10-22 19:49 UTC
Ahyi Seamount
- Green
- Yellow (this volcano)
- Orange
- Red
- Aviation colour codeDiffers
- YELLOW
- Ground alert levelDiffers
- ADVISORY
- Monitored byDiffers
- Northern Mariana Islands
- Coordinates (USGS registry)
- 20.44° N, 145.03° E
- Latest USGS notice
- 2026-10-22 23:16 UTC
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The link names the volcanoes by USGS identifier. If one later drops off the elevated list, the page says so.
Colour codes and alert levels: two scales
Aviation colour code
GREEN, YELLOW, ORANGE or RED. Written for pilots and airlines: it describes the hazard a volcano poses to aircraft, mainly from airborne ash.
Ground alert level
NORMAL, ADVISORY, WATCH or WARNING. Written for communities and emergency managers: it describes the hazard on the ground near the volcano.
USGS reports both for every volcano, and they usually move together (GREEN with NORMAL, YELLOW with ADVISORY, ORANGE with WATCH, RED with WARNING), but each is its own assessment for its own audience. This page shows both exactly as USGS supplies them.
- REDWARNING
- A hazardous eruption is imminent, underway or suspected.
- ORANGEWATCH
- Unrest is heightening or escalating and an eruption is possible, or an eruption is underway with limited hazards.
- YELLOWADVISORY
- Unrest is above the volcano’s known background level. It does not mean an eruption is imminent.
- GREENNORMAL
- Typical background activity. Not listed here unless USGS reports it as elevated.
Summarised from USGS alert-level definitions; the notice linked for each volcano is the authoritative statement. USGS alert levels (opens in new tab)