Waves of bubbles in basaltic magmas and lavas

Initially homogeneous uspensions of bubbles in basaltic magmas and lava flows may become unstable and form rising waves or layers of bubbles. We derive a set of model equations for the two-phase (bubble-liquid) system and present the results of a linear stability analysis and numerical simulations. Periodic vesicle layers are preserved in Columbia l•iver flows with a spacing of •1 m; the prediction of the Stability analysis combined with a simple model for solidification of the lava suggests that vesicle layers may represent waves of bubbles formed within the flow. The spacing of layers is determined by a balance between the growth of bubbles and hydrodynamic self-diffusion. Vesicular layers preserved in Columbia l•iver flows may thus form by hydrodynamic processes and do not require the repeated injection of fresh volatile-rich magma or a periodic nucleation of bubbles. Waves of bubbles may also develop in magma chambers and conduits and could play a role in eruption dynamics.