Nav: Home

Gas causing ground to rise near Bay of Naples volcano

July 12, 2016

New work by Italian geochemists seems to indicate that the current ground movement around one of the world's most dangerous volcano systems may be due to gas pressure, and not because of a surge of volcanic magma. This work was recently presented at the Goldschmidt conference in Yokohama, Japan (30 June 2016).

The Campi Flegrei (Phlegraean Fields), just across the Bay of Naples from the famous Vesuvius volcano, is amongst the most dangerous volcanos on Earth. In the past it has been capable of a "VEI 7" eruption (Volcanic Explosivity Index of 7, meaning that it has produced an explosive eruption even bigger than the famous Krakatoa eruption of 1883). However, this was around 40,000 years ago. The last eruption, "VEI 2" occurred in 1538 AD.

Because of the geological instability in the area, the land in this area can rise and fall by several metres over just a few years, a phenomenon known as Bradyseism. The last few years have seen the ground in the area begin to rise again, with a 38 cm rise recorded since late 2005*. There have been worries that this may presage an eruption.

The last serious geological unrest in the area was in 1982-84, which saw ground levels rise by up to 1.8m. Most scientists think that the movement in this period was caused by mixed magmatic- hydrothermal activity (although some recent papers in the geochemical literature have suggested a major role for hydrothermal processes supported by deep magmatic gases, with pressurised water causing the land to rise). On the other hand, consensus exists that the current activity is caused by molten magma movement and accumulation under the Campi - which carries a greater risk of an eruption. Now however, a group of Geochemists from Second University of Naples and the Vesuvius Observatory think that the consensus has got it exactly the wrong way round.

Lead researcher, Professor Roberto Moretti (Seconda Università degli Studi di Napoli) commented:

"Everyone accepts the geochemical evidence that current activity has different causes to that of 1982-84. Most geochemists are now showing that the 1982-84 movement was caused by hydrothermal activity and the current activity is caused by magma, but we think that it's exactly the other way round. We have checked geochemical records going back over more than 30 years, and our ongoing interpretation - looking at released gases and physical signals - seem to be consistent with current activity being hydrothermal, with the support of deep magmatic gases, rather than due to magma migration or growth of a shallow (3-4 km deep) magma chamber. We believe that this magma dynamics characterized the 1982-84 episode.

This is apparently better news, at least for now; activity in which magma moves upward and accumulates tends to be associated with an increased chance of an eruption. However the change from hydrothermal to magmatic activity can take place at any time, so we're not in a position to say that everything is well under the Campi Flegrei. The Campi Flegrei is still a very volatile place. What it does show is the difficulty in interpreting the data, even from one of the most-studied volcanic areas in the world. Reconciling all of the data is a major issue, despite our efforts.

Achieving such a unique and consistent interpretation would probably require direct access to underground geochemical, geophysical and geochemical information in the areas of interest. However, there is still a debate over the safety of drilling in such a volatile area".

Commenting, Professor Jon Blundy (University of Bristol) said:

"Interpreting the causes of ground movement at restless volcanoes is an enduring problem for volcanologists. Both hot gases (steam) and magma are candidate causes, but with quite different implications for future eruptive activity. Moretti and others make a compelling case for gas, rather than magma, as the cause of the latest bradyseisms at Campi Flegrei. Their methods could be used at other restless volcanoes where there is evidence of ground uplift"
-end-


Goldschmidt Conference

Related Magma Articles:

Volcanic crystals give a new view of magma
Volcanologists are gaining a new understanding of what's going on inside the magma reservoir that lies below an active volcano and they're finding a colder, more solid place than previously thought, according to new research published June 16 in the journal Science.
Thermal history of magma may help scientists hone in on volcanic eruption forecasts
A new study analyzed crystals of the mineral zircon -- zirconium silicate -- in magma from an eruption in the Taupo Volcanic Zone in New Zealand about 700 years ago to determine the magma's history.
Crystals once deep inside a volcano offer new view of magma, eruption timing
Volcanologists are gaining a better understanding of what's going on inside the magma reservoir that lies below New Zealand's Mount Tarawera volcano.
Forget the red hot blob: Volcanic zircon crystals give new view of magma
The classic red teardrop of magma underneath a volcano peak is too simplistic.
Deep magma reservoirs are key to volcanic 'super-eruptions', new research suggests
Large reservoirs of magma stored deep in the Earth's crust are key to producing some of the Earth's most powerful volcanic eruptions, new research has shown.
New study documents aftermath of a supereruption, and expands size of Toba magma system
The rare but spectacular eruptions of supervolcanoes can cause massive destruction and affect climate patterns on a global scale for decades -- and a new study has found that these sites also may experience ongoing, albeit smaller eruptions for tens of thousands of years after.
Copper-bottomed deposits
Researchers at UNIGE have studied over 100,000 combinations to establish the depth and number of years required for magma to produce a given amount of copper.
The Deccan Traps: Double, double magma trouble
A new study suggests that roughly 65 million years ago, not just one plume of magma, but two, fueled the mass eruption along the Deccan Traps, an event that contributed to one of the greatest extinction events on Earth.
The secret of the supervolcano
Researchers have now found an explanation for what triggered the largest volcanic eruption witnessed by mankind.
Modeling magma to find copper
About 70 percent of the copper comes from deposits formed several million years ago during events of magma degassing within the Earth's crust just above subduction zones.

Related Magma Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".