Rome airport is threatened by gas eruptions

Cracks in the subsurface of the Tiber delta cause gases to rise from the deep underground

Gas crater at the Fiumcino airport two weeks after the first eruption © Ciotoli et al.
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Only a few hundred meters away from Rome Fiumcino airport, a crater suddenly opened in August 2013, from which gas is rising to this day. Now it turns out that the entire Tiber delta is interspersed with a network of cracks in the ground. Through these gaps, gases and gas-rich liquid from the depth can penetrate upwards. The risk of further gas outbreaks is therefore very high - even on the airport grounds, as Italian researchers warn in the journal "Geophysical Research Letters".

On August 24, 2013, a strange phenomenon in Italy caused astonishment: just 800 meters from Rome Fiumcino airport, gas suddenly began to shoot up from the ground. The eruption gave rise to a small, water-filled crater in which wild bubbling gas bubbles rose. Over time, the crater was getting bigger, after a month he already had a diameter of three meters. In September, a further gas eruption occurred in a nearby closed down well, further outgassing followed.

The proximity to the airport and the city of Rome made local authorities worried, especially since there are no signs that these outgassings stop in the foreseeable future. Giancarlo Ciotoli from the State Institute for Environmental Protection in Rome and his colleagues have therefore studied the emerging gas and geology of this area - also to be able to estimate future risks for the airport and the city.

Carbon dioxide from great depth

The analyzes revealed that the gas rising from the subsurface is predominantly carbon dioxide, mixed with small proportions of methane. Such a composition is typical of volcanic and geothermal active areas, the researchers said. However, the gas eruptions are just over 30 miles from the nearest volcanic area. "A gas emission from deep underground layers are unusual and unexpected for the coastal plain of the Tiber, " say Ciotoli and his colleagues. Because actually the thick sediment cover of the estuary would have to prevent gas-rich liquids from rising up from the depth.

That the gas must come primarily from deeper rock layers, the researchers determined based on the isotopic signature of the gas. It contains a significantly higher proportion of the carbon isotope C-13 than the surface or only in low-depth layers. The carbon dioxide must therefore either come from the mantle or from deeply buried limestone. display

High risk in the entire Tiber delta

But how did it get to the surface? As the geological investigations have shown, the subsoil of the Tiber delta is less dense than expected. Instead, the researchers discovered a whole network of active structural weaknesses and faults that could cause gases and gas-rich liquids to reach the surface.

"The existence of several outgassings in this area, combined with the sometimes high levels of CO2 in the soil, suggests that there are gas rich sediments throughout the Tiber Delta, " Ciotoli and his colleagues said. But that means there is a risk of gas outbreaks across the area. Also Fiumcino airport and its runways are not excluded. "High CO 2 and methane concentrations can also occur within the airport area, after all, the runways are located only about 700 meters from the ongoing since August gas outbreak. (Geophysical Research Letters 2014; doi: 10.1002 / 2013GL058132)

(Wiley, 10.01.2014 - NPO)