Chiodini, G. CO2/CH4 ratio in fumaroles a powerful tool to detect magma degassing episodes at quiescent volcanoes.
It could be oozing out of the interior of the planet through erupting or even quiescent volcanoes, or through hot springs.
However, recent events at Mayon in 2013 with 5 casualties (Venzke 2013) and Ontake in 2014 with at least 57 casualties (Kato et al. 2015) demonstrate that the impact of localised phreatic eruptions is not to be underestimated by the authorities and that the risk at frequently visited, apparently quiescent, volcanoes might be higher than anticipated.
We apply the code to two small waveform datasets recorded at an active (Mount St. Helens) and at a quiescent (Mount Vesuvius) volcano.
Proximity to an active volcanic district, including quiescent Vesuvius Volcano, provides an easily identifiable stratigraphic marker (Campania Grey Tuff or CGT), up to 55 m thick, emplaced 39 ky cal BP by a large-volume explosive pyroclastic eruption.
During the quiescent stage the volcano's mouth would be obstructed, whereas in the eruptive stage it would be almost continuously open.
During the quiescent stage the volcano's mouth would be obstructed, whereas in the eruptive stage it would be almost continually open.
The application of manned aircraft, however, is limited to quiescent states of volcanoes to avoid risks to the operators.
This observation supports the conclusions that although fumaroles are the most visible surface manifestations of thermal activity, they are not necessarily the biggest contributors to the total CO2 output from quiescent, Solfatara-stage volcanoes, where CO2 is mainly released in silent, invisible form through soil emissions.
Our test site is Furnas volcano, a quiescent polygenetic volcano located in the eastern part of São Miguel island, in the Azores, an archipelago of nine volcanic islands located in the North Atlantic Ocean at the triple junction between American, Eurasian, and Nubian plates (Searle 1980).
The type of explosive activity may be defined on the basis of the information derived from the past behavior of the volcano, currently quiescent since 1944.
