GEOPHYSICS: Three Strikes and You're Out

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Science  27 Sep 2002:
Vol. 297, Issue 5590, pp. 2171c
DOI: 10.1126/science.297.5590.2171c

A large bolide hit the Yucatan Peninsula of Mexico about 65 million years ago, as revealed by the Chicxulub impact crater and the layers of debris at the Cretaceous-Tertiary (K-T) stratigraphic boundary in North America, Europe, Africa, New Zealand, and the Pacific and Atlantic Oceans. The K-T impact event was a global catastrophe that probably led to the demise of the dinosaurs and other organisms whose lifestyles were disrupted by the impact and by post-impact effects such as wildfires and nuclear winter-like conditions.

Kring and Durda have modeled the energetics and trajectories of heterogeneous particles, including gravity and shape explicitly, from their launch in the vapor plume or ejecta curtain to their return to a rotating Earth. They find that some (12%) of the vapor plume ejecta escapes from Earth, while most of the remaining material falls to the surface in daily pulses over 3 days. Although debris is distributed globally, the highest concentrations occur near Chicxulub and its antipode, roughly where India was situated at the end of the Cretaceous. The repeated intense heating of the atmosphere in these regions would likely have ignited multiple wildfires, ensuring the destruction of fauna and flora. — LR

J. Geophys. Res. 107, 10.1029/2001je001532 (2002).

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