USGS volcano updates use two related but distinct scales. The Volcano Alert Level describes conditions and hazards relevant to people on the ground. The Aviation Color Code describes concern about volcanic ash in the atmosphere. Read both values, the issue time, and the notice text together; a single color is not a complete summary of a volcano’s hazards.
INTERACTIVE FIELD GUIDE
Two scales. Choose each independently.
The ground alert describes hazards for people on the ground. The aviation code describes concern about volcanic ash. There is no fixed one-to-one pairing.
VOLCANO ALERT LEVELGround hazards
NormalTypical background conditions or a return to that state.
AVIATION COLOR CODEVolcanic ash
GreenNo ash concern or a return to background conditions, as described by USGS.
These are separate assessments, not a combined MagmaAlert prediction. Read the original notice and its issue time.
The four Volcano Alert Levels
The terms move from typical background conditions toward a hazardous eruption. They summarize the observatory’s assessment in a particular notice; they are not a countdown or a prediction of an exact eruption time.
Normal
Typical background, non-eruptive activity—or a return to that state after elevated activity.
Advisory
Signs of unrest above the volcano’s known background, or decreased activity that still merits close monitoring.
Watch
Heightened or escalating unrest with increased eruption potential and an uncertain timeframe; it can also describe an eruption with limited hazards.
Warning
A hazardous eruption is imminent, underway, or suspected. Read the notice and follow local authorities’ instructions.
The four Aviation Color Codes
The aviation scale concerns ash that can affect aircraft. Green and Yellow broadly indicate background conditions and elevated unrest. Orange indicates heightened or escalating unrest, or an eruption with no or minor ash emissions. Red indicates an imminent, ongoing, or suspected eruption with significant ash emissions likely or occurring. The notice may include plume-height information when available.
Why the two labels may not match
Ground hazards and aviation hazards are different. For example, an eruption dominated by lava flows may create serious local hazards but little ash for aircraft; an ash plume can affect aviation even when ground hazards are more limited. USGS therefore does not treat a particular alert term and color as a guaranteed pair. Check both fields in the current notice and read its explanation.
A quick way to read a volcano update
- Check the volcano name and the notice’s issue time.
- Read the ground Volcano Alert Level and the Aviation Color Code separately.
- Look for the observed change, its location, and the evidence the observatory describes.
- Open the linked Volcano Activity Notice (VAN) for ground-focused status information or the Volcano Observatory Notice for Aviation (VONA) for aviation information.
- For safety decisions, follow the responsible observatory and local emergency authorities.
MagmaAlert presents selected public notices and links to their publishers. A missing, delayed, or simplified dashboard value should not be used to infer current conditions; open the original notice for its full context.
Primary sources
Written by the MagmaAlert team for general education. This guide paraphrases USGS material, is not produced or endorsed by the USGS, and is not an emergency alert or safety assessment. Send a correction if you find an error.