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The interaction of the Cretaceous/Tertiary extinction bolide with the atmosphere, ocean, and solid Earth

John D. O'Keefe and Thomas J. Ahrens
The interaction of the Cretaceous/Tertiary extinction bolide with the atmosphere, ocean, and solid Earth (in Geological implications of impacts of large asteroids and comets on the Earth, Leon T. Silver (editor) and Peter H. Schultz (editor))
Special Paper - Geological Society of America (1982) 190: 103-120

Abstract

The mechanics of large-scale (approximately 10-km diameter) asteroidal, cometary, and meteoroid swarm impact onto a silicate Earth covered by water and a gas layer (atmosphere) demonstrate that only approximately 15% to approximately 5% of the energy of 15 to 45 km/s bolides is taken up directly during the passage through the ocean and atmosphere, respectively. Upon impact with the Earth, approximately 10 to 10 (super 2) times the bolide mass of water or rock can be ejected to the stratosphere: however, only approximately 0.1 bolide masses is in < 1 mu m particles. The vaporized, melted, and (< 1 mm) solid ejecta transfer up to approximately 40% of their energy to the atmosphere and possibly oceanic surface water, giving rise to a short, possibly lethal (to large animals) heating pulse. The initial high-speed ejecta that lofted to and above the stratosphere early in the cratering flow is enriched in bolide material and has concentrations of extraterrestrial material in the range of those measured (0.01 to 0.2) in the Cretaceous/Tertiary (C/T) boundary layer. We suggest that the origin of the C/T boundary layer is this ejecta, which is heavily shocked and in the < l-mu m range and, hence, once entrained in the stratosphere may be spread worldwide. Penetration of the atmosphere by the bolide creates a temporary hole in the atmosphere surrounded by strongly shocked air. The resultant inward and upward flow of the shocked atmosphere backward along the bolide trajectory lofts the vapor, fine-melted and solid ejecta to heights greater than 10 km. The larger, millimeter- to centimetersize, melt droplets that are lofted by this mechanism reenter the atmosphere and may represent microtektites and tektites. Sufficient impact-induced vapor, melted and comminuted silicate is ejected to stratospheric heights to markedly reduce the light levels at the Earth"s surface. The short-term effects of heating, followed by dust and possibly water-cloud deck induced worldwide cooling, provide several mechanisms to cause severe environmental stress to biota and possibly give rise to the varied and massive extinctions that occurred at the C/T boundary.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 190
Title: The interaction of the Cretaceous/Tertiary extinction bolide with the atmosphere, ocean, and solid Earth
Title: Geological implications of impacts of large asteroids and comets on the Earth
Author(s): O'Keefe, John D.Ahrens, Thomas J.
Author(s): Silver, Leon T.editor
Author(s): Schultz, Peter H.editor
Affiliation: Calif. Inst. Technol., Seismol. Lab., Pasadena, CA, United States
Affiliation: Calif. Inst. Technol., Dep. Geol. Planet. Sci., Pasadena, CA, United States
Pages: 103-120
Published: 1982
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Meeting name: Conference on geological implications of impacts of large asteroids and comets on the Earth
Meeting location: Snowbird, UT, USA, United States
Meeting date: 19810919Oct. 19-22, 1981
References: 43
Accession Number: 1983-039467
Categories: Geomorphology
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 1983
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