Understanding USGS Volcano Alert Levels

When monitoring volcanic activity, the United States Geological Survey (USGS) employs a standardized, two-part alert system. This system consists of Volcano Alert Levels (intended to inform people on the ground) and Aviation Color Codes (intended to inform the aviation sector about airborne ash hazards).

At MagmaAlert, you will constantly see these statuses shifting. Understanding what they mean is crucial for interpreting the data correctly.

This is the baseline state for most monitored volcanoes. It indicates that the volcano is exhibiting typical background activity in a non-eruptive state. For volcanoes that have recently erupted, returning to Normal means that all monitoring data (seismic, deformation, gas) have returned to pre-eruption background levels.

An Advisory indicates that a volcano is showing signs of elevated unrest above its known background level. This could mean an increase in small earthquakes (seismic swarms) or slight ground deformation indicating magma movement deep underground. An Advisory does not guarantee an eruption will happen, but it warrants closer monitoring by scientists.

A Watch is issued when a volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain. Alternatively, it is issued when an eruption is underway but poses limited hazards. For example, Kīlauea is frequently at an Orange Watch when it is safely erupting within the confines of its summit crater, away from communities.

A Warning signifies a highly hazardous eruption is either imminent, underway, or suspected. This alert level indicates significant danger to life and property on the ground, or a massive ash plume threatening aviation routes. When a Warning is issued, local authorities take immediate action, and residents in hazard zones must be prepared to follow emergency instructions.

Source data for alert definitions is provided by the USGS Volcano Hazards Program. MagmaAlert processes these alerts in real-time to ensure you have the latest information.