The flanks of a volcano often attract settlement due to rich agricultural soil which are created by falling volcanic ash and volcanic rock. It is the high population density caused by this that can explain why two-thirds of all volcanically related deaths have been recorded in Indonesia. In 1815 a massive eruption shook the Tambora volcano. The height of the mountain was reduced by 1,400 m, leaving a caldera 12 km in diameter. About 12,000 people died immediately after the event, although a further 80,000 persons eventually perished through the disease and famine which followed the destruction of crops by volcanic ashfall over a wide area of Indonesia.
Volcanic eruptions are the source of multiple hazards.
World-wide they have been responsible for killing, on average, about 650 people per year in the 20th century up to 1982 and it is estimated that more than a million people have been killed by volcanic eruptions in the past 2,000 years. Most deaths occur on few eruptions. For example 29,000 people died in the port of Saint Pierre on the island of Martinique in the Caribbean after an eruption in 1902. There are only 2 known survivors from the whole town. The historical record however probably does not provide a reasonable guide to future risk from volcanic hazards.