Mount Etna and the 1971 eruption - Rheological features of the 1971 Mount Etna lavas

Abstract

Rheological studies on the 1971 Mount Etna lavas indicate they underwent rapid transition from Newtonian to non-Newtonian fluids near their point of emission and that the non-Newtonian regime may be coincidental with high mechanical energy/low heat energy regime further from the boccas. Darcy's equation quantifies the surface roughness of channels using the Chezy coefficient and is plotted against Reynolds number on a Stanton diagram. The relation is linear, and the critical value Re$_{\text{c}}$ is not exceeded, proving wholly laminar flow. The lava underwent a divergent, twin spiral motion involving two dimensional laminar flow. Convergent, twin spiral motion occurred only where lava passed through a constriction at a relatively high velocity.