Volcanic hazard

A schematic diagram shows some of the many ways that volcanoes can cause problems for those nearby.

Volcanic hazards are threats to life and/or infrastructure due to volcanic activity.

According to John Ewert and Ed Miller in a 1995 publication, "a great majority of the world's potentially active volcanoes are unmonitored". Of the historically active volcanoes in the world, less than one fourth are monitored. Only twenty-four volcanoes in the entire world are thoroughly monitored for activity. They also state that "seventy-five percent of the largest explosive eruptions since 1800 occurred at volcanoes that had no previous historical eruptions".