Tidal modulation of eruptive activity at open-vent volcanoes: evidence from Stromboli, Italy

The role of Earth tides as a relevant controlling factor of a variety of geological processes, including seismicity and volcanism, is widely debated. Stromboli Volcano, Italy, is well known for its persistent explosive activity and represents an ideal setting to investigate tidal effects on the energy release and eruptive behaviour of volcanoes. Herein, we report new evidence that tidal stresses may modulate the timing of eruptive activity at volcanoes in an open-vent state. We report statistically significant correlations of the peak eruption frequencies to fortnightly tidal maxima (i.e. full and new moon) during a 17-month-long period of activity in 2010-2011: in fact, the number of explosive events per hour increases by >85% during tidal maxima with respect to the average values. We suggest that tidally induced cycles of compression-decompression of country rocks controls fluctuating magma supply rate from the shallow plumbing system and, thus, eruption frequency.