Combining spherical-cap and Taylor bubble fluid

Basaltic activity is the most common class of volcanism on Earth, characterized by magmas 12 of sufficiently low viscosities such that bubbles can move independently of the melt. Following 13 exsolution, spherical bubbles can then expand and/or coalesce to generate larger bubbles of 14 spherical-cap or Taylor bubble (slug) morphologies. Puffing and strombolian explosive activity are 15 driven by bursting of these larger bubbles at the surface. Here, we present the first combined model 16 classification of spherical-cap and Taylor bubble driven puffing and strombolian activity modes on 17 volcanoes. We furthermore incorporate the possibility that neighboring bubbles might coalesce, 18 leading to elevated strombolian explosivity. The model categorizes behavior in terms of the 19 temporal separation between the arrival of successive bubbles at the surface and bubble gas volume 20 or length, with the output presented on visually intuitive two-dimensional plots. The categorized 21 behavior is grouped into the following regimes: puffing from a) cap bubbles; and b) non22 overpressurised Taylor bubbles; and c) Taylor bubble driven strombolian explosions; each of these 23 regimes is further subdivided into scenarios whereby inter-bubble interaction does/doesn't occur. 24 The model performance is corroborated using field data from Stromboli (Aeolian Islands, Italy), 25 Etna (Sicily, Italy) and Yasur (Vanuatu), representing one of the very first studies, focused on 26 combining high temporal resolution degassing data with fluid dynamics, as a means of deepening 27 our understanding of the processes which drive basaltic volcanism. 28