Not that we should need reminding of their lethal potential, of course. In the last 500 years, volcanic eruptions have been responsible for the deaths of more than 275,000 people, research suggests, many of whom were killed by related secondary hazards such as tsunamis and starvation resulting from crop failure.
While the past few decades have witnessed relatively few deaths related to volcanoes, this can mostly be put down to luck rather than improved warning systems or disaster management planning. Simply put, major eruptions haven’t occurred near major population centres.
Despite this, there are certainly several volcanoes across the globe that pose a huge risk to human life. But how can we assess which are the most dangerous? A number of factors are important including the volcano's eruption history, the type of eruption it tends to produce, and, significantly, its proximity to human populations.
Here are our deadliest picks:
Mount Vesuvius, Italy
Famed for the catastrophic eruption of 79 A.D. that destroyed the Roman city of Pompeii, Vesuvius certainly deserves to be considered one of the most dangerous volcanoes on Earth. While it has been quiet since 1944, it has produced several large, explosive eruptions in the past few thousand years. These eruptions also have a tendency to generate destructive pyroclastic flows—fast-moving streams of scalding hot gas and volcanic matter which can reach speeds of up to 430 miles per hour. Furthermore, Vesuvius lies right next to the city of Naples, while more than 6 million people live within 100 kilometers (62 miles) of the mountain, according to the Global Volcanism Program.
Mount Merapi, Indonesia
Merapi is one of Indonesia’s most active volcanoes and has been continuously erupting in some form since 1548. A whopping 24.7 million people live in the densely populated areas surrounding the volcano, with the city of Yogyakarta (population 2.4 million) lying just 17 miles away. Furthermore, thousands of people live in villages dotted across the flanks of the mountain. Much like Vesuvius, one of the biggest threats Merapi poses is its ability to produce pyroclastic flows and lahars—destructive currents of mud or other debris—which have devastated lands surrounding the volcano throughout history and caused many fatalities . Recently, a series of eruptions in late 2010 killed more than 350 people and displaced over 250,000 local villagers.
Campi Flegrei, Italy
Naples certainly drew the short straw when it comes to location, because on the opposite side of the city to Vesuvius, is Campi Flegrei—an 18-mile wide volcanic area, or supervolcano, which lies mostly beneath the waters of the adjacent bay. The supervolcano—who’s name translates as "burning fields"—has not erupted since 1538. But recent signs suggest it may be reawakening from its slumber. For example, one recent study suggested it was entering a "critical state" which could pave the way for an eruption (although we are still no closer to knowing when this will occur). When it does happen, the effects are likely to be devastating. Campi Flegrei could be capable of producing an eruption 100 to 1,000 times greater than that of Mount. St. Helens in 1980. And roughly one million people live inside what is essentially the crater of the supervolcano, meaning they would likely be killed instantly. Furthermore, an eruption has the potential to produce an ash cloud which could blot out the sun and cool the planet.
Popocatépetl, which in the Aztec language means “smoking mountain,” is North America’s second highest volcano, lying just over 40 miles south-east of Mexico City—one of the largest urban areas in the world with a population of more than 20 million people. Popocatépetl has gone through numerous periods of activity in recent times—and throughout much of its history—although massive eruptions have been few and far between. However, its tendency to produce large plumes of ash, which coat the mountainside and can mix with water, increases its potential for producing dangerous lahars that could flow into surrounding populations.
Mount Rainier, United States
Mount Rainier, which rises 4,392 meters above the Cascade Mountains, poses a risk for a number of reasons. According to the U.S. Geological Survey, its next eruption could produce volcanic ash, lava flows and pyroclastic flows, which combined with its high elevation and proximity to the Seattle-Tacoma metropolitan area, could make for a potentially lethal combination. In addition, any eruption could melt the snow and ice at its summit, creating huge lahars which become rapidly flowing slurries of mud and boulders. Furthermore, Rainier’s composition means it often produces explosive, debris-producing eruptions.
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