The Shiva hypothesis: impacts, mass extinctions, and the Galaxy.
Abstract
The author reports on the current state of the debate on the impact theory as explanation of the huge mass extinctions in Earth history. First, he presents the case of the well-known extinction at the K/T boundary 65 million years ago, which may be related to the impact of a huge asteroid or comet causing the crater of Chicxulub on the Yucatan peninsula with a diameter of 200 km. Radiometric dating of the crater puts this event right at 65 million years ago. The author then describes the evidence for the 5 major and about 20 minor mass extinctions over the past 540 million years. He discusses the correlation of cratering with extinctions, and the various claims for a periodicity pattern in the extinction history. Finally, he examines the various hypotheses about a Galactic cause of the impacts. Most of these hypotheses postulate a disturbance of the Oort comet cloud by some form of Galactic local tidal field affecting the solar system.
- Publication:
-
Planetary Report
- Pub Date:
- February 1998
- Bibcode:
- 1998PlR....18....6R
- Keywords:
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- Earth History: Impact Phenomena;
- Oort's Cloud: Tidal Effects