Geochemistry, Mineralogy, Volcanology Research Spotlight

Deep Drilling Reveals Puzzling History of Campi Flegrei Caldera

Results show that caldera collapse attributed to a super eruption almost 40,000 years ago was smaller than what scientists expected. So what might have really happened?

Source: Geochemistry, Geophysics, Geosystems


At least 10% of the global population lives within 100 kilometers of a historically active volcano. Some of these people live near a collapsed volcano, like the residents of Naples neighboring the Campi Flegrei caldera. Although a caldera may appear to be more safe than a volcanic cone, the potential danger for natural hazard is not gone.

A collapse is often triggered by rapid magma loss from the magma chamber, usually following an eruption, so the hollow cone of the volcano caves in on itself. However, calderas can remain active. Two massive eruptions in the past caused the Campi Flegrei caldera to collapse: the Campanian Ignimbrite, which occurred 39,000 years ago, and the Neapolitan Yellow Tuff, which occurred 15,000 years ago.

But scientists—and residents around the caldera—fear another eruption to come. Right now, the alert for the Campi Flegrei caldera has been raised from “base” volcanic activity to “attention” status.

Researchers examine drill cores to trace the history of the Campi Flegrei caldera.
Drilling workers and scientists recover a cored sample for further geological and biological analyses. Credit: Claudio Serio

To get an accurate understanding of the caldera, De Natale et alturned to scientific drilling. The Campi Flegrei Deep Drilling Project (CFDDP) drilled to a depth of 501 meters in western Naples, the morphological limit of Campi Flegrei caldera.

Drilling gives scientists a precise view into the deep structures of the caldera, its geothermal characteristics, and its magma chemistry. All these can reveal clues to how the caldera formed. The researchers took samples from different depths of the drill site and measured argon isotopes periodically so that they could estimate the age of various layers.

The scientists combined the isotopic ages, fossil findings, and historical sea level records to assess the history of the volcano and how Campi Flegrei changed over time. The deeper layers between 250 and 501 meters do not contain fossils, meaning that the volcano was well above sea level more than 35,000 years ago. In the shallower layers, the scientists found microfossils that indicate an ocean environment, confirming that sometime between 17,000 and 35,000 years ago, the volcano collapsed.

Researchers assess the mechanics behind a large eruption in the Campi Fegrei caldera almost 40,000 years ago.
A satellite view of the Campi Flegrei caldera, the largest volcanic feature along the Bay of Naples. Credit: Jesse Allen and Robert Simmon, NASA

The rock types and ages at the drill site also reveal a curious finding: The amount of collapse attributed to the older and larger Campanian Ignimbrite eruption is smaller than the collapse that occurred after the eruption of the Neapolitan Yellow Tuff. Although there could be many reasons for the smaller collapse after the mega eruption, the authors discuss an alternative hypothesis: that the Campanian Ignimbrite did not erupt from Campi Flegrei (which was just involved as a peripheral eruption vent), but rather from fractures to the north of the caldera. This hypothesis would explain the low-level collapse in the caldera because the magma chamber would have remained intact.

Additional results from the drill site reveal that further caldera collapse won’t extend into the central city of Naples. However, the authors conclude that there is a complex mechanism that drove the caldera collapse that requires further study to better predict future eruptions in this major metropolitan area of Italy. (Geochemistry, Geophysics, Geosystems, doi:10.1002/2015GC006183, 2016)

—Alexandra Branscombe, Freelance Writer

Citation: Branscombe, A. (2017), Deep drilling reveals puzzling history of Campi Flegrei caldera, Eos, 98, Published on 01 February 2017.
© 2017. The authors. CC BY-NC-ND 3.0
  • Photomaineac

    If I were to panic every time someone predicts a volcano to POP, I would live in fear every day!

    I predict that technology will cause more problems than every volcano on Earth!

    • Dave McLeod

      I disagree…One volcano no matter how far we have advanced will take us back to the Stone age. Olympus Mons on Mars is the possible culprit for blowing out its atmosphere. We do not have anything that capable on earth…But a volcano has potential as a planet killer. Minimal an extinction or great dying culprit at the very least on a catastrophic supervolcano eruption. Right now under the Pacific the largest super volcano ever to form is coming together. It will be millions of years before we ever have to worry about it…But that being said…Could very well be Earth’s Apocalypse of life on this planet. A hyper eruption think a supervolcano eruption on methamphetamine could destroy the atmosphere as well leaving earth lifeless and waterless. We won’t ever see it…A supervolcanic eruption however may happen within the next century or two and could very well knock us down hard in the tech department.

    • Dave McLeod

      I don’t disagree with you about the dangers of taking technology to far….The particle accelerator, dark matter research, and even autonomy could destroy us without even realizing we as gods gave the keys to our kingdom to our creations by mixing AI and robotics or defenses. That terminator or matrix rubbish that some people think could never really happen is entirely feasible no more than ten to twenty years ahead.

  • NH Native

    Just a thought here, does it seem smart to drill into a caldera? I don’t think so. I remember when James Watts wanted to drill in Yellowstone, thank God he didn’t.

    • Jeremy Hale

      You’re not wrong, and many geologists and vulcanologists agree with you. They started this drill in 2010, and it came with a lot of criticism that they could possibly set the caldera off.

    • Dave McLeod

      The pin prick drill and fill below wouldn’t be effective enough to cause destabilizing of the Caldera or allow enough venting of any applicable amount to even help vent a Caldera from eruption pressures. Keep in mind they are not even drilling near the magma source. It is to far down to the chamber and would be to hot and melt all bits but a solid diamond. However….As the other person said there are two hypothesis to this. Just remember they haven’t actually punctured the magma chamber or created a hole wide enough to fracture. Now if they decided to frack the bore hole with pressurized water it could cause enough to cause an eruption through earthquakes of synthetic origin.

      In truth fracking a super volcanoes forcing it to pop in its infancy with little melt as in the 10% factor may be worthwhile to consider before it reaches a dangerous eruptive state. Just a personal theory though.

    • Giuseppe De Natale

      Yellowstone is a National Park. We drilled into an old steel factory, now abandoned. If a drilling would be enough to cause an eruption, then all the urbanized area lying on the volcano (about 600.000 people) should be evacuated just now. Drillings at active volcanoes, generally for geothermal purposes, are very common (at Campi Flegrei, about 50 geothermal exploration drillings, down to 3 km of depth, have been made, starting since 1939). Several times they also casually intercepted a magma chamber (the last time in Iceland in 2009) and nothing occurred. In Iceland, they realized that only after three days from the contact. Anyway, we absolutely do not want to even go close to the magma, and measuring temperatures during drilling can surely avoid that, also in case of a very shallow magma batch (which we would have detected anyway by recent tomography and other analyses). In contrast, this is the most risky volcanic area worldwide, so it is absolutely compelling to understand in detail the behavior of this volcano. Drilling is the most effective way.