Effects of vapor bubbles and velocity on the cooling rates of lava and pyroclasts during submarine eruptions

Understanding the conditions behind the formation of pyroclast microtextures and lava flow morphologies is key to investigate the dynamics of submarine volcanic eruptions. Clast microtextures and lava flow morphologies depend on their eruption rate and the rate of solidification. The solidification time scale is a function of heat exchange between lava and the external water, however, the effects of lava flow or clast velocity along with two-phase (liquid water+vapor bubbles) water boiling regime on the solidification time scales are poorly constrained. Using high temperature laboratory experiments, we investigate the effect of relative motion between external water and lava on its cooling time scale. A range of water speed (0-12.5 cm s-1) was used in the experiments while keeping the experimental sample stationary. This simulated a range of relative speed between lava and ambient water. Using heat transfer modeling, we find that sample-to-water heat flux overall increases with increasing water speed, along with coefficient of heat transfer up to ~1.72 × 10 Wm-2 K-1. We discuss the implications of such high heat flux from the surface of lava to external water on the formation of solid lava crusts under submarine conditions.