Two recent supereruptions (magnitude (M) scale ≥ 8), the Young Toba Tuff (YTT), Sumatra, and the Los Chocoyos (LCY), Guatemala, are found to be statistically synchronous at ca. 74 ka and near antipodal. Such planetwide synchroneity of supereruptions is shown to be statistically non-random implying a causal link. We propose that the seismic energy release from the YTT supereruption may have initiated eruption from the contemporaneous “perched” LCY magma system. This near-equatorial supereruption “double-whammy” may be the more compelling source of the significant environmental impacts often attributed to a singular YTT eruption.

Large Igneous Provinces (LIPs) are among the greatest magmatic events in Earth history withvolumes in excess of ∼500,000 km3 of predominantly basaltic lavas covering hugecontinental and ocean regions (>100,000 km2). Field observations suggest that lava flowfields in LIPs are made largely of sheet pāhoehoe lava lobes and the 10-100 m thick flows areformed by inflation. Understanding the emplacement history of these lava lobes can help usinfer the magnitude and temporal dynamics of past events.We use a phase-field model to describe solidification and re-melting of sequentially emplacedlava flows. We calibrate model parameters using field measurements at Makaopuhi lava lakeand perform extensive numerical simulations by varying the thickness of individual flow and thetime intervals between eruptions. These results help quantify the complex interplay betweenthermal evolution, flow thickness and emplacement frequency. If flows are thick enough andthe interval between emplacement short enough, reheating and re-melting may remove thetextural record of flow contacts – making flows appear thicker than they actually were. Guidedby field observations in Columbia River Basalt and Deccan Traps, we illustrate how the finalmorphology of sequentially emplaced lava is controlled by both the time scale of emplacementintervals and the time scale of cooling. We summarize our results to provide theoreticalconstraints on the thickness and emplacement intervals of individual LIP lava flows.