Dozens of volcanoes are always active
At any given time, approximately 40–50 volcanoes worldwide are in some state of eruption or elevated unrest. The Smithsonian Institution's Global Volcanism Program tracks this continuous activity through its weekly Volcanic Activity Report, compiled from observatory reports, satellite observations, and aviation advisories.
Most of this activity receives little public attention because it occurs at remote volcanoes, involves effusive (non-explosive) eruption styles, or produces effects confined to the immediate summit area. The events that make headlines are the exceptions — explosive eruptions that affect aviation, generate pyroclastic flows reaching populated areas, or produce ash fall over cities.
Persistent eruptions in the spotlight
Several volcanoes maintain long-running eruptions that fluctuate in intensity but never fully cease. Kilauea in Hawaii, Stromboli and Etna in Italy, Dukono and Semeru in Indonesia, and Sakurajima in Japan are among the most consistently active volcanoes on Earth. Their activity provides continuous data for volcanic research and testing of monitoring technologies.
For communities living near persistently active volcanoes, eruptions are not rare emergencies but recurring features of life. Alert level systems help these communities distinguish between baseline activity (which can be lived with) and escalations (which require evacuation or protective action). The challenge is maintaining public attention and preparedness during long periods of routine activity.
Elevated unrest and what it means
Volcanic unrest — increased seismicity, ground deformation, gas emissions, or thermal output without eruption — can precede eruptions by days, weeks, months, or even years. Observatories raise alert levels when unrest increases, but elevated unrest does not always lead to eruption. Many unrest episodes end without an eruption, making the decision of when to order evacuations one of the most difficult calls in natural hazard management.
Aviation color codes (green, yellow, orange, red) provide standardized communication about volcanic hazards to aviation. When a volcano is at orange or red, pilots are alerted to potential ash clouds in the region. These codes appear in EONET events and are tracked by PlanetSentry, providing users with the same information available to airline dispatchers and air traffic controllers.
How PlanetSentry tracks volcanic events
Volcanic events on PlanetSentry come primarily from EONET, which captures eruptions and elevated activity detected by satellite thermal sensors, reported by volcanic observatories, or identified through aviation advisories. Each volcanic event on the globe represents confirmed activity significant enough to be cataloged by NASA's Earth Observatory Natural Event Tracker.
The event feed provides a curated view — not every volcano is displayed, only those with activity sufficient to generate satellite-detectable signatures or formal observatory reports. For users wanting comprehensive volcanic monitoring, the Smithsonian GVP weekly reports and the USGS Volcano Hazards Program provide deeper coverage for US and global volcanoes respectively.