Giant Meteor Impacts and Great Eruptions: Dinosaur Killers?

Abstract

the way for new, different organisms has generated both great enthusiasm and controversy (Alvarez et al. 1980, 1988, Alvarez 1983, 1986, 1987, Silver and Schultz 1982). An extension of this concept proposes that comet showers are the force behind pulses of extinction and renewal every 26-50 million years (Davis et al. 1984, Hut et al. 1987, Rampino and Stothers 1984, Raup and Sepkoski 1984, Whitmire and Jackson 1984). An alternative scenario offers giant periodic volcanic eruptions as the cause of extinction (Courtillot et al. 1988, Cox 1988, Duncan and Pyle 1988, McLean 1988, Officer et al. 1987). It has even been suggested that giant impacts or comet showers may combine with or trigger periods of intense volcanism to create global catastrophes (Alvarez 1986, Cox 1988, Officer et al. 1987, Rampino and Stothers 1988). The various hypotheses of impact and volcanic events have been used to explain the extinction of dinosaurs and their flying pterosaur relatives approximately 65 million years ago. In the geologic record this corresponds to the boundary between the Cretaceous and Tertiary periods (the K-T boundary), at the end of the Mesozoic era. However, the evidence provided by a series of natural tests challenges both the impact and volcanic scenarios for dinosaur extinction. Multiple giant impacts and periods of supervolcanism earlier in the Mesozoic appear to have had no discernible effect on the dinosaurs and