There are about 20 supervolcanoes on Earth. But the term is criticized by researchers: experts do not see a serious danger.
Magma bubbles beneath the vineyards and thermal baths of southern Italy, forming one of the most active volcanic systems in the world in a region known as Campi Flegrei.
Outside of Naples, the Campi Flegrei is not a typical volcanic mountain, but rather a bowl-shaped depression dotted with craters. Stinking steam billows from vents, mud gurgles from pools, and small earthquakes shake the hundreds of thousands of residents living at the mouth of the volcano. Mythology says that Campi Flegrei, which means “burning fields” in Italian, is associated with the gates of hell.
It is also known as a supervolcano, a rare but unofficial name for volcanoes that have caused the most powerful eruptions in Earth’s history. The Campi Flegrei supereruption occurred about 39,000 years ago (as determined by rock records) and spewed gases and nearly a trillion gallons of molten rock, blocking sunlight and causing severe cooling. The most recent, much smaller eruption occurred in 1538 and created a mound of earth about 120 meters high.
Months of seismic activity at Campi Flegrei – more than 2,500 magnitude 4.3 earthquakes since September – have raised fears that the volcano could soon erupt again. But researchers say supervolcanoes don’t work that way and doubt this is a prophetic eruption.
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What does it mean to be a supervolcano?
“When a volcano is called a supervolcano, what it really means is that it has had a supereruption at least once in the past,” says Christopher Kilburn, a volcanologist at University College London. “But that doesn’t mean there will be more supereruptions in the future. . . . “Very, very, very large eruptions are much, much rarer.”
Scientists can’t see what’s happening beneath the surface of Campi Flegrei with the naked eye, but Kilburn said the recent activity could be underground molten rock and fluids realigning. These movements become visible on the surface as earthquakes.
“This alone does not mean there is an outbreak,” Kilburn said. The volcano has shown ground deformation and earthquakes in the past, but there have been no subsequent eruptions. But as activity resumes after a long time, “it’s natural to be a little worried that this could happen.”
There are only about 20 supervolcanoes on Earth
Of the more than 1,000 known volcanoes in the world, only about 20 are so-called supervolcanoes. Technically, they are the ones that obtain the highest score on the volcanic explosiveness index, which ranges from V0 (non-explosive) to V8 (colossal eruptions). Such a supereruption expels a volume of about 1,000 cubic kilometers or more, about a thousand times larger than Mount Saint Helens (V5), which caused landslides, fires, floods and more than 50 deaths in 1980.
The last eruption of V8 occurred about 27,000 years ago in Taupo, New Zealand. These violent volcanic eruptions usually leave behind a depression called a caldera, rather than a volcanic cone. According to Kilburn, this is because eruptions spew out a large amount of material (molten rock stored several kilometers below the surface) in a very short period of time. The ground becomes unstable and sinks.
If you don’t pay attention to these depressions, you can miss them, he says.
“You can drive a car through the caldera and come out the other side without realizing you’ve done just that, because the changes are quite smooth,” Kilburn said.
After the massive eruption ends, Kilburn says the volcano returns to “normal,” sometimes producing normal-sized eruptions at the bottom of the caldera. In other words, a supervolcano has nothing to do with “super” after it erupts, so the term is somewhat misleading.
Yellowstone is one of the most famous supervolcanoes in the world
Yellowstone, one of the world’s most famous supervolcanoes, measures 30 by 45 miles and attracts millions of tourists to its park. Its largest eruption took place 2.1 million years ago and expelled more than 2,400 cubic kilometers of material. As with many caldera systems, most Yellowstone eruptions since then have been much smaller.
Supervolcano is a made up word
Supervolcano is “a made-up word,” says volcanologist Michael Poland, senior scientist at the Yellowstone Volcano Observatory. “I think it’s misleading. I think it is being misapplied. I can’t stand that term. I wish it would go in the trash, but it’s too sexy.”
Like Superman or Superstar, Supervulkan also sounds too Hollywood for your taste. It involves an apocalyptic-type explosion, but as far as we know, no explosive volcanic eruption has ever caused a mass extinction, he said.
The largest volcanic explosion in the geological record is believed to have occurred about 74,000 years ago in Toba, Indonesia, and reached V8 on the volcanic explosiveness index. Some scientists initially speculated that the eruption nearly wiped out humanity because populations declined soon after, but archaeological evidence showed that Homo sapiens prospered further after the eruption.
“No explosive volcanic eruption that we know of has ever been linked to a mass extinction of plants or animals,” said Poland, who is also a scientist with the United States Geological Survey (USGS). “But that doesn’t mean it wouldn’t be devastating or difficult to survive.”
What would happen in a Yellowstone supereruption?
Many speculate what would happen if there were another supereruption in Yellowstone. According to the USGS, surrounding states would be affected by fast, hot avalanches of volcanic ash, pumice, gases and rocks. Falling ash could remain hundreds of kilometers away and be transported around the world. Small aerosol particles emitted by the volcano would reflect sunlight back into space, causing cooling on the Earth’s surface and affecting agriculture.
But scientists are skeptical that a supereruption could happen again in Yellowstone. According to the USGS, the volcano may not even have enough molten magma beneath its caldera to trigger an eruption.
Additionally, Kilburn doesn’t think “anyone believes there will be another supereruption” at Campi Flegrei in the near future. However, a smaller eruption could have a significant impact as more than 1 million people live in and around the area. Local authorities issue alerts and prepare evacuation plans based on the activity of the volcano.
Local authorities must “consider the possibility of an outbreak,” Kilburn said. “I’m not saying it’s likely, but they would be remiss to ignore that possibility.”
About the Author
Kasha Patel writes the weekly Hidden Planet column, which covers scientific topics surrounding Earth, from our inner core to the space storms headed toward our planet. It also reports on weather, climate and environmental issues.
We are currently testing automatic translations. This article was automatically translated from English to German.
This article was first published in English on November 10, 2023 on “Washingtonpost.com”; as part of a cooperation, it is now also available in translation for readers of the IPPEN.MEDIA portals.