Crashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minutePC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
In the U.S. Geological Survey (USGS) system, a volcano has two separate ratings: a word-based Volcano Alert Level for hazards affecting people and infrastructure on the ground, and an Aviation Color Code for airborne volcanic-ash conditions. The labels are status summaries, not universal evacuation orders or precise countdowns to an eruption.
Use the level to find the latest official Volcano Activity Notice (VAN), read which hazards are occurring or possible, and then follow instructions from the local emergency authority responsible for your area. Aviation operators should use the accompanying Volcano Observatory Notice for Aviation (VONA) and relevant aviation advisories.
What the two alert systems measure
The USGS framework describes volcanic conditions in two dimensions because the danger to people on the ground can differ from the danger to aircraft. Lava, lahars, ashfall, volcanic gases, rockfall and other hazards may threaten communities while producing little ash at flight levels. Conversely, an eruption can send significant ash into the atmosphere while ground hazards near the volcano remain limited.
Free tools Windows power users keep installed
One-click scans. No signup required.
| System | Primary audience | What it characterizes | Read next |
|---|---|---|---|
| Volcano Alert Level (word) | People, infrastructure and emergency managers on the ground | Overall volcanic status, unrest and ground-hazard context | Volcano Activity Notice (VAN) and local emergency instructions |
| Aviation Color Code | Pilots, dispatchers, air-traffic services and aviation authorities | Conditions involving volcanic ash in the atmosphere | Volcano Observatory Notice for Aviation (VONA) and aviation advisories |
The word and color often change together, but they are not interchangeable. Neither system is a universal global standard: other countries and observatories may use different names, colors or action criteria. The definitions below are the USGS meanings for volcanoes within its area of responsibility.
#1 Best Overall
USGS Volcano Alert Levels: what each word means
NORMAL
NORMAL means the volcano is in its typical background, non-eruptive state. A volcano can still have ordinary seismicity, gas release or other background processes at this level. NORMAL does not mean the volcano has no hazards under any circumstances; it means monitoring shows no activity above the established background for that volcano.
After a period at a higher level, observatories may return the status to NORMAL when elevated activity has ended and conditions have returned to background.
ADVISORY
ADVISORY means unrest is elevated above known background. Scientists have detected changes such as increased earthquakes, deformation, gas emissions or other signals, but the level alone does not say that an eruption is certain or imminent.
ADVISORY can also follow a higher level when activity has decreased substantially but remains above background or could increase again. Continue reading notices rather than treating the word as either an all-clear or an evacuation command.
WATCH
WATCH means unrest is heightened or escalating, with increased potential for an eruption but uncertain timing. It can also describe an eruption that is underway but currently poses limited hazards.
Rank #2
WATCH is therefore not a time estimate. It does not mean an eruption will begin within a set number of hours or days. The accompanying notice should explain which observations prompted the change, what hazards are possible and where they may occur.
WARNING
WARNING means a hazardous eruption is imminent, underway or suspected. This is the highest ground-facing level in the USGS scale, but the word alone still does not identify the affected valleys, roads, communities or hazard types.
A WARNING may involve lava flows, lahars, pyroclastic activity, heavy ashfall, volcanic gases or combinations of hazards. Read the current VAN and obey local evacuation, shelter, road-closure and access instructions immediately.
UNASSIGNED
UNASSIGNED indicates that there is insufficient information to assess the volcano’s current status. It is not a reassuring low tier and should not be interpreted as equivalent to NORMAL. Look for an observatory explanation and rely on local authorities if information is incomplete.
Aviation Color Codes: what GREEN, YELLOW, ORANGE and RED mean
GREEN
GREEN indicates typical background, non-eruptive conditions for aviation purposes.
Rank #3
YELLOW
YELLOW indicates elevated unrest above known background. It may also be used after a higher code when activity has decreased significantly but monitoring continues for a possible renewed increase.
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →ORANGE
ORANGE indicates heightened or escalating unrest with increased eruption potential and uncertain timing, or an eruption with no or minor volcanic-ash emissions.
RED
RED means significant ash emission into the atmosphere is likely with an imminent eruption, or that an eruption is underway or suspected with significant ash emissions. Aviation notices may include an estimated ash-plume height when that information is available.
These colors focus on airborne ash and aircraft safety. They are not color-coded public evacuation orders. A community can face serious lava or lahar danger while the aviation code remains ORANGE, and aircraft can face major ash danger while ground hazards near the volcano remain limited.
Why the word and color can differ
The two ratings answer different questions, so a mismatch is possible and meaningful.
Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →| Example pairing | What it can indicate |
|---|---|
| WARNING / ORANGE | A hazardous eruption is imminent, underway or suspected on the ground, but ash emissions pose limited aviation hazards. |
| WATCH / RED | Ground hazards remain limited at that point, while significant ash emissions could affect aircraft. |
Do not average the two ratings or assume one is a translation of the other. For a person near the volcano, the word-based level and its VAN matter most. For an aircraft operator, the color code, VONA and aviation advisories are the critical information.
What to do when a volcano alert changes
No single action table applies to every volcano. Wind, eruption style, topography, drainage channels, infrastructure and your distance from the vent all change the risk. Use this sequence whenever you see a new level or color.
- Identify the volcano and update time. Confirm that the notice applies to the volcano near you and check when it was issued. Conditions can change quickly.
- Read the accompanying notice, not just the label. A VAN explains the activity, potential or current hazards and likely outcomes for people on the ground. A VONA provides aviation-specific information.
- Match the hazard to your location. Determine whether the notice discusses lava, lahars, ashfall, airborne ash, gases, ballistic rocks or another threat that can reach your community, route or workplace.
- Check local emergency-management instructions. Look for official evacuation zones, shelter or masking guidance, road closures, restricted areas and transport information from the authority responsible for the affected area.
- Act on the local instruction. If officials order evacuation, leave by the specified route and follow their timing. If they order sheltering or access restrictions, comply even if the alert word alone sounds less severe.
- Monitor subsequent official updates. Use the USGS Volcano Notification Service or your observatory’s official channels for notices, but do not treat an email or text alert as a replacement for the full notice or a local emergency warning.
If you are flying, operating an aircraft or dispatching flights, consult the VONA and aviation authorities rather than relying on a ground-focused public summary.
How observatories decide when to change a level
Volcano observatories monitor around the clock with seismometers, cameras, satellite observations and other instruments. They look for signals of magma movement, changes in deformation or gas output, and evidence of active lava or ash.
There are no fixed numerical thresholds that automatically advance every volcano from one level to the next. Hawaiian Volcano Observatory geologist Natalia Deligne wrote, “Knowing exactly when to change the Volcano Alert Level and Aviation Color Code can be challenging.” She also wrote, “We do not have set thresholds: each situation is different.”
Scientists consider the volcano’s monitoring record, its past unrest and eruption patterns, and the physical processes they believe are occurring. A change is based on scientific judgment and multiple observations rather than a simple countdown clock. The notice should explain why the level changed and what scientists think may happen next based on the current consensus.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.VANs, VONAs and official updates
Volcano Activity Notice (VAN)
A VAN is issued when the Volcano Alert Level changes or when significant activity occurs within an existing level. It provides information about ground hazards such as lava flows, lahars, ashfall and airborne ash, volcanic gases and other relevant threats.
Volcano Observatory Notice for Aviation (VONA)
A VONA is the aviation-specific notice. It is issued for a change in Aviation Color Code or significant activity within the current code. It is designed to provide the information aviation decision-makers need, including ash observations and, when possible, plume-height estimates.
Observatory scientists prepare these notices from monitoring networks, direct observations and satellite sensors. Read the date, time, volcano name, current level or code, stated hazards and expected developments in each notice.
Common misunderstandings to avoid
- “ADVISORY means an eruption is about to happen.” It means unrest is above background; it does not establish certainty or imminence.
- “WATCH gives a time-to-eruption estimate.” The potential is increased, but timing remains uncertain.
- “WARNING automatically tells everyone to evacuate.” WARNING signals a hazardous eruption, while the local authority determines who must evacuate, where to go and by which route.
- “RED is the most dangerous level for everyone.” RED is about significant airborne ash and aviation risk. Ground hazards may be more serious under a different color.
- “UNASSIGNED means nothing is happening.” It means there is not enough information to assign a status.
- “The alert label is all I need.” The notice contains the location, hazard type, timing and expected outcomes needed for a practical decision.
A quick interpretation guide
| If you see | Interpret it as | Your next step |
|---|---|---|
| NORMAL / GREEN | Background conditions for the relevant system | Keep ordinary awareness and use official notices for any change. |
| ADVISORY / YELLOW | Unrest above background, or a monitored decline after higher activity | Read the notice and identify whether your location is exposed to a stated hazard. |
| WATCH / ORANGE | Heightened potential with uncertain timing, or an eruption with limited ash or ground hazards | Prepare to follow local instructions and monitor updates closely. |
| WARNING / RED | Hazardous eruption on the ground and/or significant ash danger to aviation, depending on the dimension | Follow local emergency or aviation instructions immediately; use the relevant VAN or VONA for details. |
| UNASSIGNED | Status cannot be assessed from available information | Seek clarification from the observatory and local authorities; do not assume low risk. |
The USGS alert system is a concise way to describe changing volcanic conditions, not a substitute for a current hazard notice. The safest interpretation is always specific: which volcano, which hazard, which location, which authority and which update time.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
