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

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. Plain Language Summary: The observation of thick basaltic lava flows has long been explained by vertical inflation. Here we explore an additional mechanism that could also create thick lava flows, where a sequence of thinner lobes that are emplaced on top of each other could fuse into one larger flow. Our analysis suggests the formation of thick lobes and flows by merging can occur if the lobes are emplaced relatively close to each other in time. Key Points: Lava lobes can heat and melt underlying lobes if erupted in close enough successionBased on the time between successive eruptions, there are three regimes for lava lobe cooling: fused, in parallel, and in sequenceMacroscopic structures may not reflect the original lobe thicknesses [ABSTRACT FROM AUTHOR]