There are approximately 20 supervolcanoes on Earth. But the term is criticized by researchers: experts do not see an acute danger.
Magma boils beneath the vineyards and spas of southern Italy, forming one of the world’s most active volcanic systems in a region known as Campi Flegrei.
Outside Naples, the Campi Flegrei is not a typical volcanic mountain, but rather a bowl-shaped depression dotted with craters. Stinky vapors billow from vents, mud bubbles from pools, and small earthquakes shake the hundreds of thousands of residents who live in the volcano’s mouth. Mythology says that the Campi Flegrei, which in Italian means “burning fields”, are 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 gas and nearly a trillion liters of molten rock, blocking sunlight and triggering 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 may soon erupt again. But researchers argue that supervolcanoes don’t work that way and doubt 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 due to realignment of underground molten rock and fluids. These movements become visible on the surface as earthquakes.
“This alone does not mean there is an epidemic,” Kilburn said. The volcano has shown ground deformations and earthquakes in the past, but no eruptions have followed. But as activity resumes after a long time, “it’s natural to be a little worried that this might 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 these are those that have the highest score in the volcanic explosiveness index, which ranges from V0 (non-explosive) to V8 (colossal eruptions). Such a supereruption ejects a volume of about 1,000 cubic kilometers or more, about a thousand times larger than Mount St. Helens (V5), which caused mudslides, fires, floods, and more than 50 deaths in 1980.
The last V8 eruption occurred about 27,000 years ago in Taupo, New Zealand. Such violent volcanic eruptions typically leave behind a depression called a caldera, rather than a volcanic cone. According to Kilburn, this is because eruptions eject 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 it, because the changes are quite subtle,” 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 the “super” after the eruption, 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 x 45 miles and attracts millions of tourists to its park. Its largest eruption took place 2.1 million years ago and ejected more than 2,400 cubic kilometers of material. As with many caldera systems, most Yellowstone eruptions since then have been much smaller.
Supervolcano is an invented word
Supervolcano is “a made-up word,” says volcanologist Michael Polonia, senior scientist at the Yellowstone Volcano Observatory. “I think it’s misleading. I think it was misapplied. I can’t stand that term. I wish it would end up in the trash bin, but it’s too sexy.
Like Superman or Superstar, Supervulkan also seems too Hollywood for his tastes. This implies an apocalyptic 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 approximately 74,000 years ago in Toba, Indonesia, and reached V8 on the Volcanic Explosivity Index. Some scientists initially hypothesized that the eruption nearly wiped out humanity because populations declined shortly afterward, but archaeological evidence has shown that Homo sapiens thrived 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 Polonia, who is also a scientist with the US 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 was another Yellowstone supereruption. Surrounding states would be hit by fast, hot avalanches of volcanic ash, pumice, gas and rock, according to the USGS. The 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 the Earth’s surface to cool and affecting agriculture.
But scientists are skeptical that a supereruption could happen again in Yellowstone. According to the USGS, the volcano may not have enough molten magma beneath its caldera to trigger an eruption.
Additionally, Kilburn doesn’t believe “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 the area and surrounding areas. Local authorities issue warnings and prepare evacuation plans depending on volcano activity.
Local authorities must “consider the possibility of an epidemic,” Kilburn said. “I’m not saying it’s likely, but they would be remiss if they ignored that possibility.”
About the author
Kasha Patel writes the weekly Hidden Planet column, which covers scientific topics affecting Earth, from our inner core to the space storms headed toward our planet. He also deals with 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 collaboration it is now also available in translation for readers of the IPPEN.MEDIA portals.