Effect of relative lava-water motion on the spreading and fragmentation of submarine lavas

Abstract:

Understanding the conditions behind the spreading and morphology of lava flows are key for estimating the effusion rates and investigating the dynamics of volcanic eruptions under submarine conditions. The spreading of lava during submarine eruptions primarily depends on the competing effects of the flow rate and the rate of solidification. While the initial effusion rates are governed by the subsurface plumbing architecture, the rate of solidification is a function of heat exchange between the surface of lava and the water. Using analog high temperature laboratory experiments with re-melted igneous rock, we investigate the effect of relative motion between lava flow and water on the lava cooling time scales. We use a range of water speed (up to 12.5 cm s^-1) in our experiments to simulate a range of relative motion between lava and seawater. Using our experimental time-temperature data along with transient heat transfer modeling, we quantify the convective heat transfer coefficients (up to 1.74 x 10³ Wm^-2K^-1) corresponding to the heat flux from lava to seawater at a given water speed. We find that overall the heat flux from the surface of lava to water increases with increasing speed of water. Using scaling analysis, and thermal properties of lava and seawater, we discuss the implications of our findings on the formation of lava flow morphology and hyaloclastite during submarine volcanic eruptions.