Soil radon measurements as a potential tracer of tectonic and volcanic activity

In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential
as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of
the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon
measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is
sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the
meteorological parameters. Soil samples were analyzed to characterize their uranium content. All
data have been summarized in a physical model which identifies the radon sources, highlights the
mechanism of radon transport and envisages how such a mechanism may change as a consequence of
seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m,
with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February
2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and
third had a volcanic origin. These results mark a significant step towards a better understanding of the
endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

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