Every year, an average of more than 50 volcanoes erupt around the world. For instance, the Cumbre Vieja volcano on La Palma, one of Spain’s Canary Islands, off the coast of Morocco, is currently erupting, and has thus far destroyed 500 buildings and caused the evacuation of two villages.
Many eruptions are minor, but occasionally a historic blast causes massive amounts of damage. Pyroclastic flow — a fast-flowing current of hot ash, lava, and gasses — and mudflow can bury farms, towns, and forests for miles around a volcano. Tsunamis, triggered by avalanches of debris pouring into the ocean, can wreck coastal settlements, destroy ships, and damage fisheries.
And volcanic eruptions can wreak havoc not only on the area directly around the blast, but on the entire world. Ash clouds that enter the stratosphere during an eruption are known to cause shifts in the climate that sometimes last for years and have been implicated in devastating famines throughout history. Some are even credited with ending ancient civilizations and empires. (Here are 25 ancient civilizations destroyed by natural disasters.)
24/7 Wall St. has compiled a list of the most devastating volcanic eruptions in history, using data from the U.S. Geological Survey and other sources. Many of these have caused millions of dollars worth of damage, as well as loss of life and homes, as people are forced to relocate to unaffected areas. Eruptions were chosen for the list based on the extent of the property damage and fatalities they cause, their impact on the environment, and their sheer force.
The force of eruptions is measured on a scale called the Volcanic Explosivity Index (VEI), which takes into account how much material is ejected from the volcano, as well as the height at which it is ejected into the atmosphere and the duration of the eruption. The highest VEI ever recorded is a 7, which is 10 times more powerful than a VEI of 6. Many of the eruptions on the list are ranked as a 6 or 7, making them some of the biggest natural disasters in history. (Here is the worst natural disaster in every state.)