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Anatomy of a giant impact: Characterization of the K/T boundary event from distal ejecta

Wednesday, April 27, 2005
Bruce
Bohor (USGS, Denver & Univ. of Colorado, Boulder)

Giant terrestrial impacts are fairly rare in the geologic record, but some of them have had enormous effects on earth history. One of these is the asteroid impact 65 Mya that caused the extinction of >65% of the extant species, including the dinosaurs, and formed the basis for dividing the Cretaceous (K) from the Tertiary (T) Periods, as well as marking the boundary between the Mesozoic and Cenozoic Eras.

Using principles of forensic geology, the size, type and, ultimately, the location of the impact crater were discovered, although the latter involved some luck as well. Detailed analyses of the distal ejecta components revealed that the cratering mechanics involved two distinct stages (processes) of ejection, which resulted in far-reaching consequences to life on earth. These parameters may also be applicable to large impacts on other planets with atmospheres.

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