Volcanoes of the World

The Earth has many hundreds of volcanoes that have been active in recent geological time, scattered across the continents and the ocean floor. They are not spread evenly: most lie along the boundaries of the tectonic plates, and a large share encircle the Pacific Ocean in the belt known as the Ring of Fire. Others rise from hot spots in the Earth's mantle, far from plate edges, and a great many remain hidden as submarine volcanoes beneath the sea.

Several individual volcanoes are well known from history and ongoing activity. Vesuvius, near Naples in Italy, is remembered for the eruption in the year 79 that buried the Roman towns of Pompeii and Herculaneum. Also in Italy, Etna on Sicily is one of the most active volcanoes in the world, and nearby Stromboli has erupted so persistently that it has been nicknamed the lighthouse of the Mediterranean. The same volcanic region of southern Italy includes Ischia and the Campi Flegrei. In the United States, Mount St. Helens erupted dramatically in 1980 in the Pacific Northwest.

Volcanoes also differ in form. Steep, cone-shaped stratovolcanoes, built from alternating layers of lava and ash, include many of the famous explosive peaks, while broad, gently sloping shield volcanoes are built from runny lava flows. Because eruptions can endanger nearby populations, active volcanoes are monitored by observatories that track ground movement, gases and small earthquakes in an effort to forecast when an eruption may occur.

Frequently asked questions

Which volcano destroyed Pompeii?

Mount Vesuvius, near Naples in Italy. Its eruption in the year 79 buried the Roman towns of Pompeii and Herculaneum under ash and debris.

What is a stratovolcano?

A steep, cone-shaped volcano built from alternating layers of lava and ash. Many of the world's most famous and explosive volcanoes are of this type.

How are dangerous volcanoes watched?

Volcano observatories monitor ground movement, volcanic gases and small earthquakes, using these signs to help forecast possible eruptions.