Experimental approach to rootless eruptions using kitchen materials

Abstract

Rootless eruption is caused by lava flow entering inland water or wet sediment and forms craters and cones far from the actual vent. Since the rootless eruption can be significantly explosive, the possibility of rootless eruption is critical for hazard management; however, forecasting occurrence and explosiveness of a rootless eruption remains difficult because explosiveness is considered to correlate nonlinearly with the mass ratio of hot lava and water. Here, we show the nonlinear nature of this type of eruption roots from the nonlinearly determined area between lava and underlying wet sediment as a function of water content within the wet sediment by a series of analog experiments can be implemented in a kitchen. In our analog experiment, lava and wet sediment were replaced by heated syrup and mixture of baking soda (sodium bicarbonate) and cake syrup. From measurements of mass loss due to CO 2 gas emission during the heat-induced decomposition of baking soda, we estimated the reaction efficiency for various proportions of baking soda and cake syrup in the substrate. We observed a nonlinear dependence of CO 2 emission; the peak efficiency was achieved for the substrate with 15 and 35 g of baking soda and cake syrup, respectively. Considering physical properties such as density and viscosity, we found that the Rayleigh–Taylor instability between the poured heated syrup and the substrate can explain the observed nonlinear dependence of CO 2 emission. For natural settings, the results of this study suggest that both the availability of water and rheological properties of the substrate affect the occurrence and stability of hydrovolcanic eruptions.[Figure not available: see fulltext.].