There are still about 500 active volcanoes in the world
Most active volcanoes are in a great belt around the Pacific Ocean and around the Solomon Islands, New Guinea and Indonesia. There is also a group in the Mediterranean that includes Etna and Vesuvius, and there is a chain running from Tristan da Cunha through the Azores to Iceland.
These are some of the weak spots in the Earth's crust, through which molten rock, or magma, occasionally bursts. In Indonesia alone, there are nearly 30 volcanoes still giving off gases.
Many eruptions occur without causing much damage to mankind but in the last 150 years there have been at least two catastrophic eruptions. In 1883, at Krakatoa, in the Sundra Straits between Java and Sumatra, 36,000 people were killed. Nearly 20 years later, 30,000 people were killed when Mount Pelee in Martinique erupted.