¹ The last eruption is a catalogue record, not evidence of an eruption currently in progress.
Satellites & ash clouds
Understanding the map layers
Ash clouds & dispersion
VAAC centres publish ash-cloud locations and altitude ranges, with forecasts for 6, 12 and 18 hours. We map the structured fields from the NOAA NWS bulletin service. Each area has its own valid time. We do not calculate our own dispersion from surface winds.
NOAA distributes advisories from the nine VAAC centres. A current advisory or drawable area is not available for every volcano.
VIIRS detects unusually strong thermal radiation. We show detections within 20 km of catalogue volcanoes with available radiative-power and confidence values. Fires and industry can also be heat sources. Clouds, resolution and satellite overpasses limit detection. Missing points do not confirm inactivity.
Aqua / MODIS · band 31 · brightness temperature in kelvin. Clouds and atmosphere affect the image; not a direct lava temperature.
The OMPS satellite layer shows retrieved total SO₂ columns for an assumed plume altitude. The CAMS model separately shows the predicted distribution at future valid times, where available up to five days from model start. The two layers use different units. SO₂ can also come from non-volcanic sources.
Total SO₂ columns show neither an individual volcano’s daily emission rate nor directly the concentration at ground level.
Ash advisories are checked every 15 minutes; satellite metadata and heat detections hourly. Provider acquisition and valid times matter: a new retrieval is not a new measurement.