Can we imagine a natural event capable to threaten the stability of the world’s economy, alter the climate as we know it, and even threaten the lives of millions of people? Volcanic super-eruptions, hundreds of times larger than volcanic eruptions witnessed by our interdependent human civilisation, are capable of such dangerous, widespread and diverse consequences. Despite their low probability of occurrence in relation to human life-span, super-eruptions increase in probability when transposed to the time-scales of civilizations.
The Campanian Ignimbrite (CI) erupted from the Phlegrean Fields on the Bay of Naples (Italy) 39,300 years ago, and it is considered the largest eruption of the Late Quaternary in Europe. Tephra ejected from the eruption blanketed over 3 million km2 from the eastern Mediterranean Sea to the Russian Plains. Recent studies indicate that the CI would have caused a volcanic winter, possibly lowering the temperature between 6-9 ºC in Eastern Europe and Northern Asia. It has been debated if the CI eruption, boosted by the coldest and driest Heinrich event, had an effect on the Middle to Upper Paleolithic transition altering the survival of the remaining Neanderthals in Europe.
Eruption Dynamics: a two-phase Event
Geological evidence indicates that the eruption had two phases and possibly had the following sequence:
1) a short, high-intensity Plinian explosive phase injecting gas and volcanic ash high into the stratosphere,
2) density-current transport affecting tephra dispersal and deposition near the source,
3) a caldera collapse, producing large and fast flows of hot gas and rocks (pyroclastic flow) that scaled mountain ridges of more than 1 km in height,
4) a significant portion of fine-grained material was lofted from the top of the propagating currents as co-ignimbrite plumes,
5) the finer ash of the co-ignimbrite phase dispersed downwind up to thousands of kilometres away from the eruption site.
Density current
Method
We applied a novel computational approach to reconstruct, for the first time, the two phases of the Campanian Ignimbrite super-eruption. We used the FALL3D tephra dispersal model in conjunction with a downhill simplex inversion method (DSM) to infer values of the eruption source parameters. We compare the tephra dispersal and volume results from reconstructing the CI eruption as a two-phase event (Method 1), with those form conventional simplified characterization as a single-phase event (Method 2). Finally, simulation results are validated against two independent tephra deposits.
Tephra Deposits
Tephra dispersal for each phase of the CI eruption
Simulation results for the tephra dispersal indicated that the eruption began with a short, high-intensity Plinian explosive phase (brown), followed by a longer co-ignimbrite phase (blue). The volume associated to the co-ignimbrite phase accounted for 75% of the total fallout volume (red).
Combined Tephra dispersal for both phases
The eruption lasted a total of 23 hours and blanketed a large region from the eastern Mediterranean Sea to the Russian Plains. The total erupted mass was 208 km3, a volume equivalent approximately to 8 Mount Everest.
Density Current Effect
The environmental stress that followed the CI eruption, aggravated by the precedential onset of the Heinrich Event 4, provides a link between this exceptional volcanic catastrophe and the extensively discussed Middle to Upper Palaeolithic transition. Settlements proximal to the source would have been abandoned in the immediate aftermath of the eruption due to tephra fallout and severe halogen acidification. Tephra fallout from our simulations, together with the attendant episode of Fenno-Scandinavian ice cap and peripheral tundra advance on land, reduced the area available for human settlement in Europe of up to 30% (ash fallout gap). We propose that after ecosystem recovery, several decades later, modern humans would have gravitated towards repopulating the tephra fallout gap rather that overcoming biogeographical frontiers (“Ebro frontier” model). Contrary to other theories, these results suggest that the CI eruption would have led to an instance of prolonged Neanderthal survival in South-Western Europe, especially in the Iberian Peninsula.
Effect on Middle to Upper Paleolithic transition
References
· Black, B., Neely, R. & Manga, M. Campanian Ignimbrite volcanism, climate, and the final decline of the Neanderthals. Geology 43, 1–4 (2015).
· Costa, A., Macedonio, G. & Folch, A. A three-dimensional Eulerian model for transport and deposition of volcanic ashes. Earth Planet. Sci. Lett. 241, 634–647 (2006).
· Costa, A. et al. Quantifying volcanic ash dispersal and impact of the Campanian Ignimbrite super-eruption. Geophys. Res. Lett. 39, L10310 (2012).
· Costa, A., Folch, A. & Macedonio, G. Density-driven transport in the umbrella region of volcanic clouds : Implications for tephra dispersion models. Geophys. Res. Lett. 40, 4823–4827 (2013).
· Engwell, S. L., Sparks, R. S. J. & Carey, S. Physical characteristics of tephra layers in the deep sea realm: the Campanian Ignimbrite eruption. Geol. Soc. London, Spec. Publ. 398, 47–64 (2014).
· Fedele, F., Giaccio, B. & Hajdas, I. Timescales and cultural process at 40,000 BP in the light of the Campanian Ignimbrite eruption, Western Eurasia. J. Hum. Evol. 55, 834–57 (2008).
· Folch, A., Costa, A. & Macedonio, G. FALL3D: A computational model for transport and deposition of volcanic ash. Comput. Geosci. 35, 1334–1342 (2009).
· Sparks, R. S. J. & Huang, T. C. The volcanological significance of deep-sea ash layers associated with ignimbrites. Geol. Mag. 117, 425–436 (1980).
· Sparks, R. S. J. et al. Super-eruptions: Global effects and future threats. (2005).
· Stringer, C. et al. Climatic stress and the extinction of the Neanderthals in: Clim. Stress extinction Neanderthals inNeanderthal Mod. humans Eur. Landsc. last Glaciat. Archaeol. results Stage 3 Proj. 233–240 (2004).
· Zilhão, J. The Ebro Frontier : A Model for the Late Extinction of Iberian Neanderthals. Neanderthals edge150th Anniv. Conf. Forbes’ Quarr. Discov. Gibraltar 111–121 (2000).
· Zilhão, J. Neandertals and moderns mixed, and it matters. Evol. Anthropol. 15, 183–195 (2006).