Dozens of people have died, hundreds are missing and many more homes were destroyed after separate volcanic eruptions in Hawaii and Guatemala that made headlines worldwide in recent months. And although those volcano eruptions are not part of a trend, experts have said, the volcanoes in question are far from the only dangerous ones in the world.
When assessing which volcanoes are the most dangerous in the world, however, several factors come into play, including population density surrounding active volcanoes, the types of magma that emerge during eruptions and each volcano’s eruption history. For example, an explosive volcanic eruption in a remote area is not as dangerous as one in a populous region that requires mass evacuations. And volcanoes that go a long time without erupting pose a higher risk for eruption because of mounting pressure inside them.
Magma content is one way to assess a particular volcano’s danger level, according to Stanley Mertzman, a geosciences professor at Franklin & Marshall College in Lancaster, Pa. Mertzman says experts will look at the level of silica, a rock-forming compound that affects the thickness of lava and a volcano’s overall shape, according to the USGS. Silica can indicate how dangerous an eruption can be because it tends to crystallize into chains in cooling lava, increasing its viscosity, in turn creating thicker magma that can make a volcano erupt more explosively.