An experimental assessment of the ignition of forest fuels by the thermal pulse generated by the Cretaceous–Palaeogene impact at Chicxulub

Abstract

Abstract:A large extraterrestrial body hit the Yucatán Peninsula at the end of the Cretaceous period. Models suggest that a substantial amount of thermal radiation was delivered to the Earth's surface by the impact, leading to the suggestion that it was capable of igniting extensive wildfires and contributed to the end-Cretaceous extinctions. We have reproduced in the laboratory the most intense impact-induced heat fluxes estimated to have reached different points on the Earth's surface using a fire propagation apparatus and investigated the ignition potential of forest fuels. The experiments indicate that dry litter can ignite, but live fuels typically do not, suggesting that any ignition caused by impact-induced thermal radiation would have been strongly regional dependent. The intense, but short-lived, pulse downrange and at proximal and intermediate distances from the impact is insufficient to ignite live fuel. However, the less intense but longer-lasting thermal pulse at distal locations may have ignited areas of live fuels. Because plants and ecosystems are generally resistant to single localized fire events, we conclude that any fires ignited by impact-induced thermal radiation cannot be directly responsible for plant extinctions, implying that heat stress is only part of the end-Cretaceous story.

The first day of the Cenozoic

“…4E) may reflect airfall with mixing into the overlying Unit 1F by bioturbation or reworking. Wildfires can be spawned in 2 ways by a large impact: directly by the impact plume or by reentering ejecta (56,73,74). For Chicxulub, the plume is considered to emit sufficient thermal radiation to ignite flora up to 1,000 to 1,500 km from the impact site (73).…”

Earth's Impact Events Through Geologic Time: A List of Recommended Ages for Terrestrial Impact Structures and Deposits

“…Thus far, the only convincing case for impact as the trigger of a mass extinction and severe, global-scale pa-leoenvironmental effects remains the giant Chicxulub impact on the Yucatán Peninsula in Mexico, which has been stratigraphically, (micro-)paleontologically, geochemically, and in terms of precise U-Pb and Ar-Ar ages linked with the Cretaceous/Paleogene boundary at *66.05 Ma (e.g., Hildebrand et al, 1991;Kring and Boynton, 1991;Toon et al, 1997;Smit, 1999;Kring, 2007;Schulte et al, 2010;Renne et al, 2013Renne et al, , 2018DePalma et al, 2019). Some of the hazardous paleoenvironmental effects caused by the Chicxulub impact (see Kring, 2007 for a summary) include a roughly Richter magnitude 10.5 earthquake that, in turn, triggered a large-scale tsunami and, in paleolakes and lagoons, forceful seiches (e.g., Smit and Romein, 1985;Bourgeois et al 1988;DePalma et al, 2019); the global distribution of airborne distal impact ejecta (e.g., Smit, 1999;Claeys et al, 2002); shock-heating of the atmosphere and widespread wildfires caused by the fallout of hot ejecta (e.g., Wolbach et al, 1985;Melosh et al, 1990;Kring and Durda, 2002;Durda and Kring, 2004;Robertson et al, 2013;Belcher et al, 2015); an almost instantaneous phase of ''impact winter'' caused by atmospheric dust blocking the sunlight (e.g., Vellekoop et al, 2014Vellekoop et al, , 2016Brugger et al, 2017), followed by a superimposed, slower greenhouse effect in response to the voluminous release of atmospherically active gases (e.g., water vapor, CO 2 , and SO x ) from the carbonate-and sulfate-dominated target rock (Kring et al, 1996;Pope et al, 1997;Pierazzo et al, 1998;Kring, 2007); and the acidification of ocean water and leaching of soil due to acid rain (e.g., Prinn and Fegley, ...…”

No Evidence for a Large Atmospheric CO2 Spike Across the Cretaceous‐Paleogene Boundary

“…A recent model for the vaporization of target carbonate bedrock at Chicxulub suggests a modest 54 ppm rise in atmospheric CO 2 (Artemieva & Morgan, 2017). Global wildfires may have caused CO 2 to increase by 315 ppm (Toon et al, 2016), but the extent of these fires is contentious and may have been far less (Belcher, 2009;Belcher et al, 2003Belcher et al, , 2004Belcher et al, , 2005Belcher et al, , 2009Belcher et al, , 2015Harvey et al, 2008;Morgan et al, 2013).…”