The Earth's crust, on which we live and depend, is in large part the product of millions of once-active volcanoes and tremendous volumes of magma, some of which did not make it to the Earth's surface. Volcanic ash increases soil fertility for forests and agriculture by adding nutrients and acting as mulch. Groundwater heated by hot magma can be tapped for geothermal energy. This hot groundwater has also concentrated valuable minerals, including copper, tin, gold and silver, which are mined throughout the world.

Scientists have estimated that at least 200,000 people have lost their lives as a result of volcanic eruptions during the last 500 years. The 1902 eruption of Mount Pelée in Martinique was the deadliest volcanic eruption in the Caribbean with nearly 30,000 deaths.

This eruption occurred in 1912 at Novarupta in Alaska. An estimated 15 cubic kilometers of magma was explosively erupted during a 60-hour period starting on June 6th, 1912. Fortunately there were no casualties and little property damage due to the isolation and sparse population of the region affected.

An eruption occurs when magma rises from a storage reservoir within the Earth and reaches the surface of the Earth. As it rises, the magma has to push its way through existing rocks, often causing swelling of the ground and small earthquakes.