Two supervolcanoes, a world apart, have the attention of scientists

Denise Chow
Updated Wed, November 1, 2023 

Two long-dormant “supervolcanoes” on two separate continents appear to be stirring to life. Well, maybe.

In recent months, more than a thousand minor earthquakes have rattled the area around the Campi Flegrei volcano in southern Italy, stoking fears that it may soon erupt again after nearly five centuries. Some 6,000 miles away, scientists have for decades recorded similarly small earthquakes and instances of ground deformation at the Long Valley Caldera, a volcano in eastern California that sits adjacent to Mammoth Mountain.

But does all this seismic unrest really portend a volcanic eruption? It sort of depends on whom you ask.

Most experts say there is no immediate threat of an eruption at either Long Valley or Campi Flegrei. Both volcanoes are calderas — sprawling depressions created long ago by violent “super-eruptions” that essentially collapsed in on themselves — which are often more challenging to forecast compared to the large mountain-shaped features that people typically imagine when they think of volcanoes.

Seismic unrest can be a sign that a volcano is waking up, but the full story is much more complex.

Both Campi Flegrei and the Long Valley Caldera are known as supervolcanoes, a term used to describe a volcano that at one time has erupted more than 240 cubic miles of material. Michael Poland, a geophysicist at the U.S. Geological Survey and the scientist-in-charge of the Yellowstone Volcano Observatory, said that while Campi Flegrei and Long Valley are capable of huge explosions, the supervolcano moniker can be misleading.

“The first thing people think is that there’s going to be a civilization-ending eruption,” Poland said. “You can have an impactful explosion at these places, but the vast majority are smaller eruptions with less explosive lava flows.”

That hasn’t quieted concern in the communities that border the caldera systems. The Italian city of Naples and its surrounding towns are all in close proximity to Campi Flegrei, and local government officials have been planning how to evacuate tens of thousands of people from the area, if needed.

Italy: Solfatara di Pozzuoli (Vincenzo Izzo / Sipa USA via AP file)

The last time Campi Flegrei erupted was in 1538, and one of the system’s biggest explosions occurred around 39,000 years ago.

In September, the former head of the Vesuvius observatory at Italy’s National Institute of Geophysics and Volcanology told Reuters that the earthquake swarms were causing ground uplift in the area, which could lead to structural damage in the port town of Pozzuoli, located roughly 20 miles outside of Naples.

Christopher Kilburn, a professor of volcanology and geophysical hazards at University College London, said the last period of seismic unrest at Campi Flegrei was in the 1980s. Kilburn said the ground in the town of Pozzuoli was lifted nearly 2 meters, or almost 6.5 feet, over two years.

Still, there was no big eruption.

Fast-forward to today, and Kilburn said there are some key differences with the seismic unrest that has been observed.

“The difference is that today, the uplift has been a bit more than 1 meter, but over 20 years, not two,” he said. “And so this whole uplift has lasted 10 times longer and it has been about 10 times slower.”

Still, Kilburn thinks the current activity at Campi Flegrei indicates that the structure of the volcano’s crust is changing. In a study published in June in the journal Communications Earth & Environment, Kilburn and his colleagues used a model to analyze the volcano’s behavior and found that the crust of Campi Flegrei is becoming weaker, making it more prone to rupturing.

But even if the crust reaches its breaking point, that wouldn't necessarily have catastrophic consequences, Kilburn said.

“If there’s a rupture, there is no guarantee that magma is going to erupt,” he said. “And that’s why with the observatory there, the official releases cover anything from just an increase in seismicity through to a small eruption, because we can’t really tell where we are in that just yet.”

Calderas are often difficult to study because they are vast depressions over top of huge magmatic systems. Campi Flegrei, for instance, stretches 7 to 9 miles across. The Long Valley Caldera in California is about 10 miles wide. And one of the most famous calderas in the world, at Yellowstone National Park, measures 30 miles by 45 miles, according to the U.S. National Park Service.

Coincidentally, the Long Valley Caldera also saw an uptick in earthquake activity in the 1980s and has been seismically stirring for decades, but scientists have been less concerned overall about a major eruption there in the foreseeable future. That's because there have been signs that the magma beneath it has been cooling.

Ettore Biondi, a research scientist in the division of geological and planetary sciences at the California Institute of Technology, has tried to understand what has been unfolding in recent decades at the Long Valley Caldera.

Biondi and his colleagues published a study last month in the journal Science Advances detailing a novel way of gathering acoustic sensing data with fiber-optic cables to capture snapshots of what is happening beneath the caldera's surface.

An eruption cannot be ruled out completely, but the researchers found that a solid rock structure is actually covering the magma chamber at the Long Valley Caldera, which is likely preventing big eruptions from occurring.

“That doesn’t imply that you can’t have smaller eruptions, but from a supervolcanic eruption perspective, I think as of now we are on the safe side,” Biondi said.

He added that this method of gathering high-resolution underground images could be used at other volcano systems around the world, and particularly at ones that are not well understood. The results could help scientists better anticipate what is happening at volcanoes when they start to stir.

“For certain volcanoes, we know very well what’s going on,” Biondi said. “For other volcanoes, we have no idea.”

The inability to create reliable eruption forecasts owes largely to the fact that volcano systems are so varied. The way one volcano comes to life is not necessarily how others around the world signal an eruption is imminent.

“We have to spend a lot of time on the volcanic system, monitoring it to understand what’s normal at that volcano, and then be able to recognize when something becomes abnormal,” said Poland, of the U.S. Geological Survey.

Yellowstone, for instance, is hit by an average of around 2,000 earthquakes every year, and that seismic activity is not considered out of the ordinary, he said.

At places like Campi Flegrei and the Long Valley Caldera, scientists have been putting in the work to understand what all the rumblings and geological changes really mean.

“Volcanoes are sort of like people — they all have their own personality,” Poland said. “A big part of volcanology and monitoring active volcanoes is getting to understand the personality of the specific volcanoes that you’re interested in. And some volcanoes are noisier than others.”

This article was originally published on NBCNews.com




What’s going on with Italy’s supervolcano?
Rebecca Olds
Thu, November 2, 2023 

In this photo taken on April 30, 2016, a woman takes a close look at a steaming fumarola at the Solfatara crater bed, in the Phlegraean Fields near Naples, Italy. Phlegraean Fields — Campi Flegrei in Italian — are a sprawling constellation of ancient volcanic centers. 

| Frances D’Emilio, Associated Press

In recent months, people who live at the base of supervolcano Campi Flegrei in a town known as Pozzuoli near Naples, Italy, have been shaken by rumblings and the fear of a possible eruption.

Campi Flegrei’s caldera spans 12 to 15 kilometers (about 7.5 to 9 miles) across, making it the largest active caldera in Europe, according to a 2023 article published in the journal Communications Earth and Environment.

Campi Flegrei is about 28 miles away from Pompeii, where Mount Vesuvius famously erupted in 79 C.E.

Christopher Kilburn, author of a study on Campi Flegrei and professor of volcanology and geophysical hazards at University College London, told NBC News that research suggests that recent seismic activity is weakening the Earth’s crust and making it more prone to rupturing.

More than 2,500 earthquakes have trembled through the area since August and they continue this month, reported The Wall Street Journal.

A local fisherman told the Journal, “We’re used to it, but that doesn’t mean we aren’t afraid.”

The stirrings around Campi Flegrei have prompted Italian officials to come up with an evacuation plan if the volcano erupts, which residents say they know won’t work because of the cramped streets, per the Journal.

So the town’s 500,000 residents — and another 800,000 people who live nearby — are watching and waiting.

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When did Campi Flegrei last erupt?

Campi Flegrei last erupted nearly 500 years ago in 1538, scientists say, after a previous dormant state of 3,000 years, per 2011 research published in Quaternary Science Reviews.

The last period of increased seismic activity was more recent — in the 1980s, Kilburn told NBC News.

How likely is Campi Flegrei to erupt?

Even with the recent earthquakes and the release of sulfuric gases that are common in Pozzuoli these days, Kilburn said that it doesn’t necessarily mean that Campi Flegrei will erupt, per NBC News.

“If there’s a rupture, there is no guarantee that magma is going to erupt,” he said. “And that’s why with the observatory there, the official releases cover anything from just an increase in seismicity through to a small eruption because we can’t really tell where we are in that just yet.”

A geology professor at the University of Napes Federico II, Alessandro Iannace, told The Wall Street Journal that while the chances of a catastrophic eruption are low right now, they aren’t zero.

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The main point of concern, Iannace explained to The Wall Street Journal, is the traffic jam that would occur during an evacuation.

“The difference is that in Yellowstone, if you think the eruption is coming, you can send the tourists home and close the park for four years,” Iannace told the Journal. “You can’t do that with Campi Flegrei. There are just too many people there.”
Are there supervolcanoes in the U.S.?

The caldera located in Yellowstone National Park is one of the most famous supervolcanos in the world. It’s significantly larger than the Campi Flegrei caldera, according to the U.S. National Park Service.

In addition to the one in Yellowstone, two other supervolcanos are found in the United States: Long Valley in eastern California and Valles Caldera in New Mexico, per the U.S. Geological Survey.

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Yellowstone may have already experienced its ‘largest and most cataclysmic event’

Residents on 'Edge' Facing 2.5K Earthquakes as Italian Supervolcano Rumbles: 'It's Nonstop'

David Chiu
Thu, November 2, 2023 


Italy has been preparing for a possible mass evacuation of tens of thousands of residents


GettyPozzuoli, the super active volcano of the Campi Flegrei. Italy's government has been preparing in the event of a mass evacuation due to volcanic activity in the Campi Flegrei area

Italy’s government has been preparing for a possible mass evacuation of tens of thousands of residents due to a supervolcano that has caused 2,500 earthquakes since September, several media outlets reported.

Residents in the city of Pozzuoli, which is outside of Naples, are concerned about the recent activity since they live in the volcanic area of Campi Flegrei. As reported by Reuters, a 4.2 magnitude earthquake occurred on Sept. 27 that, while it didn’t cause any major structural damage, provided the biggest tremor in the area in over four decades.

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"Even those small ones (quakes) make us afraid," resident Annamaria Scardi told Reuters. "We are worried because (we are supposed to) run away. But where do we go? Where? This is the situation. We're on edge."

“It’s nonstop earthquakes here,” said Luca Averna, per The Wall Street Journal. “We’re used to it, but that doesn’t mean we aren’t afraid.”

Related: 'Caring' Student, 21, Dies After Falling at Least 300 Feet While Climbing Ore. Volcano

As defined by the U.S. Geological Society, a supervolcano is defined as “a volcanic center that has had an eruption of magnitude 8 on the Volcano Explosivity Index (VEI), meaning that at one point in time, it erupted more than 1,000 cubic kilometers (240 cubic miles) of material.” Relatedly, a “supereruption” is a term that describes VEI 8 eruptions. According to the agency, the largest eruption at Yellowstone occurred 2.1 million years ago with a volume of 2,450 cubic kilometers.

Italy’s official tourism website characterizes Campi Flegrei as a “dormant supervolcano, one of the few on the earth's surface.” And according to NBC News, Campi Flegrei's last eruption took place in 1538.

Related: Pilot Relives How He Escaped Volcano Eruption by Jumping Into Sea: ‘I Hit the Water, It Went Black’

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A phenomenon known as bradyseism has been attributed to the increase of recent earthquakes in the Campi Flegrei area, The Wall Street Journal reported.

Christopher Kilburn, a professor of volcanology and geophysical hazards at University College London, told NBC News that he thinks that the activity at Campi Flegrei is due to a change in the structure of the volcano’s crust. However, he said, “If there’s a rupture [in the crust], there is no guarantee that magma is going to erupt.”

Meanwhile, the Italian government reviewed the situation last month, per Reuters, and would call for an evacuation if officials feel that buildings could be prone to collapse. Nello Musumeci, a civil protection minister, said that any evacuation would take place only in the event of “extreme necessity,” The Guardian reported.

Pamphlets have also been distributed to locals in Pozzuoli on what to do in case of an eruption and its aftermath. However, as resident Claudio Correale told The Wall Street Journal: “Everybody here knows the evacuation plan is inadequate. But it’s probably not even necessary, because everybody will have left by the time the volcano erupts.”

Resident Vincenzo Russo told Reuters that the threat of eruption has divided his family in that he wants to stay while his wife and children are looking to move to another town. "When you sleep at night, the nightmare is always there. You forget the situation and you're on the couch, and then the tremor is there with you,” he said.