Lava flows destroy everything in their path	Falling volcanic ash can collapse buildings and block roads.	Lahars from volcanic eruptions destroy bridges and disrupt rivers.

Volcanic eruptions are one of Earth's most dramatic and violent agents of change. Not only can powerful explosive eruptions drastically alter land and water for tens of kilometers around a volcano, but tiny liquid droplets of sulfuric acid erupted into the stratosphere can change our planet's climate temporarily. Eruptions often force people living near volcanoes to abandon their land and homes, sometimes forever. Those living farther away are likely to avoid complete destruction, but their cities and towns, crops, industrial plants, transportation systems, and electrical grids can still be damaged by tephra, lahars, and flooding.

Volcanic activity since 1700 A.D. has killed more than 260,000 people, destroyed entire cities and forests, and severely disrupted local economies for months to years. Even with our improved ability to identify hazardous areas and warn of impending eruptions, increasing numbers of people face certain danger. Scientists have estimated that by the year 2000, the population at risk from volcanoes is likely to increase to at least 500 million, which is comparable to the entire world's population at the beginning of the seventeenth century! Clearly, scientists face a formidable challenge in providing reliable and timely warnings of eruptions to so many people at risk.

Some Effects of Volcanic Activity

Fatalities Caused by Volcanic Activity

Historical volcanic disasters since A.D. 1700 that killed more than 300 people

Photo Gallery: Effects of Volcanic Activity

| Lahars | Pyroclastic Flows |

URL of thisdocument: http://volcanoes.usgs.gov/Hazards/What/hazards.html
Last modified: October 16, 1998