The ascent of single Taylor bubbles suspended in a range of Newtonian liquids, scaled to mimic basaltic magmas, within vertical and inclined tubes has been studied experimentally over the range 0° to 70° (where 0° is vertical and 90° is horizontal). Using measurements of Taylor bubble parameters (ascent velocity and film thickness) and morphology, alongside dimensionless numbers, we show that inclination has a clear effect on bubble behaviour and morphology. Notably, ascent velocity peaks at inclinations of 40 to 50°, with proportional velocity increases of ~40-90% with respect to vertical ascent values, before decreasing again. This work provides a basis for the expansion of existing theoretical framework to accommodate for conduit inclination in volcanic scenarios.

Basaltic volcanism is the dominant mode of volcanism on Earth and exhibits a range of activity, from passive degassing to the most common explosive style: strombolian volcanism. Strombolian volcanism is driven by gas slugs, making it vital to consider the effects of variable magmatic rheology and internal vent geometry on slug flow dynamics. Emerging experimental technologies play a major role in developing our understanding of the natural complexity of such basaltic systems. This study examines slug ascent within particle-free and particle-containing media experimentally across a range of inclinations. Dimensionless parameters are derived to describe specific flow characteristics at laboratory and volcanic scales, and to demonstrate the viability of current theoretical framework. Slug ascent is shown to be dependent on its morphology, which is a function of inclination, liquid viscosity, and related controlling characteristics i.e. particle fraction. Maxima for ascent velocities and associated dimensionless parameters occur within the range 40—60°.