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The interaction of the Cretaceous/Tertiary Extinction Bolide with the atmosphere, ocean, and solid Earth

O'Keefe, John D. and Ahrens, Thomas J. (1982) 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. Special papers (Geological Society of America). No.190. Geological Society of America , Boulder, CO, pp. 103-120.

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The mechanics of large-scale (~10-km diameter) asteroidal, cometary, and meteoroid swarm impact onto a silicate Earth covered by water and a gas layer (atmosphere) demonstrate that only ~ 15% to ~ 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, ~ 10 to 10^2 times the bolide mass of water or rock can be ejected to the stratosphere: however, only ~0.1 bolide masses is in < 1 μm particles. The vaporized, melted, and (< 1 mm) solid ejecta transfer up to ~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-μm 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.

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Additional Information:© 1982 Geological Society of America. Accepted 22 June 1982. We thank the organizers of the Conference on Large Body Impacts and Terrestrial Evolution for inviting us, and we are grateful to Leon T. Silver for encouraging us to submit this paper. This research was supported under NASA Grant NSG 7129. We are grateful for the computational assistance of Michael Lainhart and Lynne Adler. We are indebted to the helpful reviews by D. Orphal and E. Jones. We thank David Stevenson for showing us the supersonic drag theory and receiving preprints from L. Alvarez, C. Emiliani and S. Gerstl. Contribution No. 3762, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.
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Caltech Division of Geological and Planetary Sciences3762
Series Name:Special papers (Geological Society of America)
Issue or Number:190
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Official Citation:Modeling the Dynamics of Large Body Impacts on Continents and Oceans: John D. O’Keefe and Thomas J. Ahrens The interaction of the Cretaceous/Tertiary Extinction Bolide with the atmosphere, ocean, and solid Earth Geological Society of America Special Papers, 1982, 190, p. 103-120, doi:10.1130/SPE190-p103
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56178
Deposited By: Tony Diaz
Deposited On:27 Mar 2015 19:12
Last Modified:10 Nov 2021 20:55

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