The shallow degassing system of Stromboli volcano: insights from geochemical and geophysical data

We present a combined analysis of geochemical and geophysical data collected at Stromboli volcano during the 2005-2007 transition from mild-high explosive to effusive activity. Soil radon concentrations have been compared with the main geophysical parameters. The coherent trend of all considered data allow us to infer the presence, at Stromboli, of an efficient shallow degassing system feds by volatiles in a steady-state regime. Increments were observed during two distinct periods, characterized by high explosive activity and related to the periodical refilling of the shallow magmatic system. Acquired data support the idea that the active volcanic system is capable to restore its typical activity after phases of conduit overpressures followed by an increase in seismic activity eventually accompanied by structural adjustment. The observed decoupling between radon activity and geophysical parameters (infrasonic activity and seimic tremor) that follow the above phases define a relationship between the local stress field and the Stromboli plumbing system. The data presented in this contribution give us the opportunity to better understand the interplay among the radon signal and the cited geophysical parameters during changes in volcanic activity that prelude a major eruptive cycle.