The Mud Volcanoes of Salse di Nirano

The mud volcanoes of Salse di Nirano are situated on the bottom of a wide, sub-circular depression covering a surface of about 10 ha, where the Plio-Pleistocene "Argille grigio-azzurre" Formation crops out. Many mud erupting bodies of various size and shape are found in the area. The caldera-like shape of this small valley may result from progressive ground subsidence owing to the continuous depletion of mud which, once ejected, flows into an underlying stream. Measurements of helium and radon Rn-222 isotopes, present in the emission gases, were carried out in order to record possible correlations with local seismicity. Observations carried out since 1986 confirmed that the eruptive activity of these pseudo-volcanic bodies is actually influenced by the release of seismic energy from foci located in the mid-Apennine region.