Some Lava Flows May Not Have Been as Thick as They Appear

Abstract

Individual lava flows in flood basalt provinces are composed of sheet pāhoehoe lobes and the 10–100 m thick lobes are thought to form by inflation. Quantifying the emplacement history of these lobes can help infer the magnitude and temporal dynamics of prehistoric eruptions. Here we use a phase-field model to describe solidification and remelting of sequentially emplaced lava lobes to explore additional processes that may lead to thick flows and lobes. We calibrate parameters using field measurements at Makaopuhi lava lake. We vary the lobe thicknesses and the time interval between eruptions to study the interplay between these factors and their impact on the thermal evolution of flows. Our analysis shows that if the time between emplacements is sufficiently short, remelting may merge sequentially emplaced lobes—making lava flows appear thicker than they actually were—which suggests that fused lobes could be another mechanism that creates apparently thick lava flows.