How dangerous are volcanoes?

Volcanic eruptions are some of the most feared natural disasters, but often they cause no significant damage Eruptions don't usually make headlines unless they have caused major loss of life or property, or are so large that they have a global impact on the atmosphere. Many people, therefore, do not realize how frequently eruptions occur and how widespread they are on our planet. There are about 600 potentially active volcanoes in the world, plus a whole lot more hidden under the seas. On average, about 50 volcanoes have eruptions each year and a dozen or more may be active in any given month. Some of these not-talked-about eruptions may be spectacular to watch – or too dangerous to go near!

Just how often do volcanoes cause major loss of life? On average, a really catastrophic eruption happens a few times per century, though our statistics are limited by rather incomplete historical records, particularly for volcanoes in the New World and in very remote locations.

Table 4.1 shows the death tolls for the most notable eruptions during the last millennia. We can gather some interesting facts from this information, such as: (1) many of the world's most dangerous volcanoes are located in the Ring of Fire; (2) pyroclastic flows (nuées ardentes) and mudflows are by far the most deadly products of a volcanic eruption; and (3) eruptions often kill by indirect means, such as by triggering tsunamis or by destroying vital crops leading to widespread starvation.