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[1] Pressurized gas drives explosive volcanic eruptions. Existing models can predict the amount and pressure of gas in erupting magma, but application and testing of such models is currently limited by the accuracy of input parameters from natural systems. Here, we present a new methodology, based on a novel integration of 1) high-speed imaging and 2) shock-tube modeling of volcanic activity in order to derive estimates of sub-second variations in the pressure, mass, and volume of gas that drive the dynamics of unsteady eruptions. First, we validate the method against laboratoryscale shock-tube experiments. Having validated the method we then apply it to observations of eruptions at Stromboli volcano (Italy). Finally, we use those results for a parametric study of the weight of input parameters on final outputs. We conclude that Strombolian explosions, with durations of seconds, result from discrete releases of gas with mass and pressure in the 4-714 kg and 0.10-0.56 MPa range, respectively, and which occupy the volcano conduit to a depth of 4-190 m. These variations are present both among and within individual explosions. Citation: Taddeucci, J., M. A. Alatorre-

Roccamonfina volcano (Roman Magmatic Province) sits at the margin of the NE-trending Garigliano graben. The most important episodes in the volcano’s history (630–50 ka bp ) have been controlled by tectonic activity associated with the graben’s master-faults. Roccamonfina volcano comprises two main parts: a stratovolcano developed inside the graben, and a complex of centres developed on the south-eastern horst. The summit of the stratovolcano is truncated by a horse-shoe shaped caldera (dimensions 6.5 km by 5.5 km) with the longest axis trending NW. The caldera opens towards the SE along NE-trending faults, which belong to the same system as the graben faults. Stratigraphical evidence indicates that caldera collapse was not caused by explosive eruptive events emplacing ignimbrites, or by sector collapse preceding ignimbrite eruptions. Geomorphological and structural observations, together with geophysical evidence, suggest that collapse of the volcano summit occurred as a mechanical re-adjustment to the high rate of the Garigliano graben extension during a climax of the regional tectonism at around 400 ka bp . The present elliptical shape of the collapsed area is due to the superposition of a linear NE-trending graben structure in the east, and a sector collapse in the west.

27We reconstructed the evolution of the volcanic activity within the central 28 Garrotxa monogenetic Volcanic

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