The 39 ka Campanian Ignimbrite (CI) super-eruption was the largest volcanic eruption of the past 200 ka in Europe. Tephra deposits indicate two distinct plume forming phases, Plinian and co-ignimbrite, characteristic of many caldera-forming eruptions. Previous numerical studies have characterized the eruption as a single-phase event, potentially leading to inaccurate assessment of eruption dynamics. To reconstruct the volume, intensity, and duration of the tephra dispersal, we applied a computational inversion method that explicitly accounts for the Plinian and co-ignimbrite phases and for gravitational spreading of the umbrella cloud. To verify the consistency of our results, we performed an additional single-phase inversion using an independent thickness dataset. Our better-fitting two-phase model suggests a higher mass eruption rate than previous studies, and estimates that 3/4 of the total fallout volume is co-ignimbrite in origin. Gravitational spreading of the umbrella cloud dominates tephra transport only within the first hundred kilometres due to strong stratospheric winds in our best-fit wind model. Finally, tephra fallout impacts would have interrupted the westward migration of modern hominid groups in Europe, possibly supporting the hypothesis of prolonged Neanderthal survival in South-Western Europe during the Middle to Upper Palaeolithic transition.

The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under the project NEMOH (REA grant agreement n° 289976). A.C. acknowledges the European Research Project MED-SUV (grant agreement 308665). The simulation runs were performed using the MareNostrum supercomputer at the Barcelona Supercomputing Center in Barcelona, Spain. We are extremely grateful to the BSC Scientific Visualization group for producing the artwork and multimedia included in this work; in particular we thank G. Marin, D. Garcia, F.M. Cucchietti, and L. Calvo. We thank X. Rubio and J. Zilhão for providing critical insights to the Middle to Upper Palaeolithic transition, and V.C. Smith, J.L. Pelegrí and F. Artigas for comments that greatly improved the manuscript.

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