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Self-shielding of thermal radiation by Chicxulub impact ejecta; firestorm or fizzle?

Tamara J. Goldin and H. Jay Melosh
Self-shielding of thermal radiation by Chicxulub impact ejecta; firestorm or fizzle?
Geology (Boulder) (December 2009) 37 (12): 1135-1138

Abstract

As hypervelocity ejecta from the Chicxulub (Yucatan, Mexico) impact fell back to Earth, the surface may have received a deadly dose of thermal radiation sufficient to ignite global wildfires. Using a two-phase fluid flow code, which includes ejecta and air opacities in a radiative transfer calculation, we modeled the atmospheric reentry of spherules arriving at distal sites. The models predict a pulse of thermal radiation at the surface peaking at 5-15 kW/m (super 2) , analogous to an oven set on "broil" (approximately 260 degrees C). Previous calculations, which ignored spherule opacity, yielded >10 kW/m (super 2) sustained over >20 min and such an extended pulse is thought to be required for wood ignition. However, the new modeling suggests that fluxes only exceed the solar norm for approximately 30 min and are only >5 kW/m (super 2) for a few minutes. Previous models failed to consider the self-shielding effect of settling spherules, which block an increasing proportion of downward thermal radiation emitted by the later-arriving spherules. Such self-shielding may have prevented widespread wildfire ignition, although the thermal pulse may have been sufficient to ignite localized fires and kill fauna lacking temporary shelter. An opaque cap of submicron dust in the upper atmosphere could, however, override the self-shielding effect.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 37
Serial Issue: 12
Title: Self-shielding of thermal radiation by Chicxulub impact ejecta; firestorm or fizzle?
Affiliation: University of Arizona, Lunar and Planetary Laboratory, Tucson, Az, United States
Pages: 1135-1138
Published: 200912
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 30
Accession Number: 2010-007908
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
N19°40'00" - N21°38'60", W90°22'00" - W87°30'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201005
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