6 volcanic eruptions worth fearing

Volcanic activity has been increasingly in the news over the last few years, and a massive eruption could have devastating global effects

(Image credit: Illustrated / Getty Images)

By Devika Rao, The Week US, Justin Klawans, The Week US

last updated 11 October 2024

There were six low-intensity earthquakes recorded beneath Mount Adams in Washington state in September 2024. Usually, "earthquakes at this volcano are located at a rate of about 1 earthquake every 2-3 years," said the U.S. Geological Survey Cascades Volcano Observatory (CVO). Mount Adams is the second-largest volcano in Washington but the largest active one in the state by area and volume.

"We are now working to gather more data to assess if this is really something unusual or just a volcano talking to us a bit more than it normally does," Jon Major, the scientist in charge at CVO, said to LiveScience. While not an eruptive volcano, the USGS still considers Adams a high-threat because flowing lava can pose a danger.

Volcanic activity has been increasingly in the news over the last few years. Italy's Mount Etna, one of the world's most active volcanoes, blew its top in August of 2023. The eruption soon "evolved into a 'lava fountain'" that produced a "volcanic cloud dispersed in a southerly direction" and forced the temporary closure of a local airport, CNN said. In 2022, Hawaii's Mauna Loa volcano — the largest active volcano on Earth — erupted for the first time in nearly 40 years. While these particular eruptions seemed to be contained, other volcanoes around the world could pose even more danger should an explosion occur. Indeed, Nature said, a massive eruption could have devastating effects "across transport, food, water, trade, energy, finance and communication in our globally connected world." Here are six other volcanoes worth fearing:

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Effects of a major eruption: If Katla goes off, its eruption will be 10 times stronger than nearby Eyjafjallajokull, which exploded in 2010, causing billions of dollars in economic damage and leaving millions of travelers stranded. A Katla eruption could have a "notable impact on the climate due to the emission of sulfur dioxide (SO₂), which can form sulfate aerosols in the atmosphere, reflecting sunlight and potentially causing temporary global cooling," said Perlan, a natural history museum in Reykjavík, Iceland. While eruptions are common in the volcano-rich Iceland, Katla's larger ash plume would shoot higher in the air and spread over larger areas of Europe for a longer period, with much more devastating effects on air travel and economic trade. Overall, an eruption could "harm agriculture, water supplies and air quality, potentially leading to health issues, particularly respiratory problems," Perlan added. As far back as 2014, there were concerns that an eruption could cause a "tsunami that propagates along the south coast of Iceland and out to sea," said a 2014 study published in the journal Natural Science — though the effects and potential damage of this are unclear.

Effects of a major eruption: Effects of a major eruption: When Cumbre Vieja last erupted in 2021, "lava poured out of the volcanic ridge, and flowed to the sea, engulfing 3000+ dwellings, said NASA's Jet Propulsion Laboratory. While thousands of people were evacuated, the damage from the eruption was not as severe as it could have been. Scientists had warned that a major eruption of Cumbre Vieja could cause the entire western flank of the volcano to fall into the sea, creating a "mega-tsunami" wherein "waves hundreds of meters high" would radiate "out into the Atlantic," the New Zealand Herald said. However, subsequent studies of the "potential consequences of a collapse at Cumbre Vieja have significantly downplayed the risk" of such an outcome.. In a 2021 report for the U.S. Geological Survey, the Hawaiian Volcano Observatory said that the theory of an eruption-prompted mega-tsunami "does not hold up to rigorous examination."

Effects of major eruption: Straddling the Andes Mountains, Cotopaxi began roaring back to life in the mid-2010s and has been rumbling on and off consistently since last year. While these eruptions have been mostly minor, a major seismic event "would produce more than 100 million cubic meters of ash — a column at least 12 miles high," volcanologist Patricia Mothes said to The Atlantic in 2017. If this were to occur, it would likely mean that "200,000 people in Cotopaxi's shadow alone would be directly or moderately affected," Mothes added. Some estimates have said that a major eruption would be even more devastating — Phys.org said in 2015 that up to 325,000 people would be immediately at risk if Cotopaxi blew its top, as the volcano's snowcapped peak would likely melt and cause massive flooding throughout the region.

Effects of major eruption: Famous for wiping out Pompeii and Herculaneum in 79 A.D., Vesuvius would do much greater damage if it erupted again today. "Given its potential, Vesuvius could endanger more than 3 million people and wipe out the city of Naples," said HowStuffWorks. The region also has a "'squatter' dilemma, with over 700,000 people residing illegally on its slopes," at risk. Vesuvius's next eruption will likely be an "incredibly forceful explosion …marked by flying rock and ash at speeds of up to almost 100 miles per hour."

Effects of a major eruption: The third-tallest active volcano in the Northern Hemisphere, Popocatépetl is only 40 miles west of Mexico City, whose metropolitan area has an estimated 22 million inhabitants, and just 30 miles east of Puebla, a city of around six million. A large eruption could send "a city-sized cloud of ash 20 centimeters thick" to "descend upon the buildings of Mexico City," Pacific Standard said. The deadly cloud would then "clog Mexico City's drainage lines, poisoning its water supplies and ceasing electricity transmission via short-circuiting," and the devastation would be accompanied by "1,000-degree lahars and pyroclastic flows" that would reach most of the towns in the immediate area.

Effects of a major eruption: When the Yellowstone Caldera, or "supervolcano," in Yellowstone National Park erupts again, "its effects would be worldwide," the U.S. Geographical Survey said. In the U.S., the closest states to Yellowstone, including Montana, Idaho and Wyoming, could be "affected by destructive pyroclastic flows, which are a mix of lava blocks, pumice, ash and volcanic gas that flows around a volcano after an eruption," said The Hill. "Much of the rest of the country could be blanketed in falling volcanic ash — in some places, it could be more than three feet deep." Globally, the volcano could also "impact the global climate by emitting ash and gas into the stratosphere, which could block sunlight and lower global temperatures for a few years," Michael Poland from the Yellowstone Volcano Observatory said to LiveScience. The resulting catastrophe could "shut down transportation, collapse buildings, short-out the electrical grid and cause massive agricultural failure," the University of British Columbia's Johan Gilchrist said to CBC Radio.

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Devika Rao has worked as a staff writer at The Week since 2022, covering science, the environment, climate and business. She previously worked as a policy associate for a nonprofit organization advocating for environmental action from a business perspective.