Gas monitoring at volcanic fields outside Naples, Italy, exposes
multiple sources of carbon dioxide emissions

Date:
March 7, 2023
Source:
Geological Society of America
Summary:
The Phlegraean volcanic fields just west of Naples, Italy, are
among the top eight emitters of volcanic carbon dioxide in the
world. Since 2005, the Solfatara crater -- one of many circular
depressions in the landscape left by a long history of eruptions
--has been emitting increased volumes of gas. Today it emits
4,000-5,000 tons of carbon dioxide each day, equivalent to the
emissions from burning ~500,000 gallons of gasoline.

Researchers estimate that as much as 20%--40% of the current carbon
dioxide emissions are from the dissolution of calcite in the rocks,
while 60%--80% is from underground magma.


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FULL STORY ==========================================================================
The Phlegraean volcanic fields just west of Naples, Italy, are among the
top eight emitters of volcanic carbon dioxide in the world. Since 2005,
the Solfatara crater -- one of many circular depressions in the landscape
left by a long history of eruptions -- has been emitting increased
volumes of gas. Today it emits 4,000-5,000 tons of carbon dioxide
each day, equivalent to the emissions from burning ~500,000 gallons of gasoline. In a new paper published ahead of print in Geologyon Thursday, researchers estimate that as much as 20%- 40% of the current carbon
dioxide emissions are from the dissolution of calcite in the rocks,
while 60%-80% is from underground magma.


========================================================================== "Estimating the source of the carbon dioxide is important to
properly reconstruct what is happening in the magmatic system and the hydrothermal system," says Gianmarco Buono, a volcanologist at Italian
National Institute of Geophysics and Volcanology and lead author of
the study. "Our aim is to provide a tool to better discriminate the contribution of magmatic and non-magmatic carbon dioxide that can
also be applied to other systems." When magma moves toward Earth's
surface, the decreasing pressure on the magma results in degassing --
the release of gases that were previously trapped inside the magma --
including water vapor, carbon dioxide, and sulfur dioxide.

Scientists monitor volcanoes for unrest and possible eruptions using
a variety of observations -- detecting earthquakes and tremors related
to magma movement, taking detailed measurements of ground deformation,
and assessing the types and volumes of gases released at the surface
from fumaroles -- openings in the earth that emit steam and other gases.

Eruptions are often preceded by increased fluxes of gas, but that does
not mean that every increase in gas emissions will be followed by an
eruption. It is also possible for carbon dioxide to come from sources
besides magma.

Interaction between hot underground fluids and host rocks can also
release carbon dioxide.

The Italian National Institute of Geophysics and Volcanology has been monitoring gas emissions from Solfatara crater since 1983, providing
a long record of the changes in volume and composition of the gases
released there. By comparing ratios of nitrogen, helium, and carbon
dioxide in the emissions, researchers had previously established that
the gases were coming from deep sources of magma.

"We focused mainly on geochemical variation, especially for carbon
dioxide, helium, and nitrogen, because they are non-reactive species. They contain information about what is happening in the magma," explains Buono.

But when the region started experiencing increased unrest in 2005, the
data began to deviate from the chemical fingerprints of the magmas, a
trend that continued to increase over time alongside rising temperatures
in the shallow hydrothermal system. The unrest continued, and in 2012
the alert level was raised from green to yellow, indicating that there
is heightened activity but not an imminent threat of eruption.

In addition to small earthquakes and higher gas emissions, the region also experienced deformation of the ground surface. Circulation of hot fluids underground could explain the rising temperatures, ground deformation,
and increased gas emissions -- interaction of hot acidic fluids with
calcite in the rocks also releases carbon dioxide. Drill cores of the
rocks from previous studies reveal that calcite in the rocks has similar composition to the gas emissions. The researchers estimate that 20%-40%
of the carbon dioxide at the Solfatara crater site was from removal of
the calcite in the host rock.

* RELATED_TOPICS
o Earth_&_Climate
# Global_Warming # Volcanoes # Air_Quality # Climate #
Forest # Natural_Disasters # Geochemistry # Air_Pollution
* RELATED_TERMS
o Carbon_dioxide o Fossil_fuel o Carbon_monoxide o
Ocean_acidification o Forest o Carbon_dioxide_sink o
Greenhouse_gas o Caldera

========================================================================== Story Source: Materials provided by Geological_Society_of_America. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Gianmarco Buono, Stefano Caliro, Antonio Paonita, Lucia Pappalardo,
Giovanni Chiodini. Discriminating carbon dioxide sources during
volcanic unrest: The case of Campi Flegrei caldera (Italy). Geology,
2023; DOI: 10.1130/G50624.1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230307144354.htm

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