The Volcanic Rival

Is he in heaven? Is he in hell? That demmed, elusive Pimpernel?' Baroness Orczy

In 1972, Peter Vogt, a volcano specialist at the U.S. Naval Research Laboratory in Washington, D.C., called attention to the huge volcanic outpourings that had occurred in India at the time of the K-T boundary and wondered if the resulting injection of poisonous trace elements into the atmosphere might not have been the cause of the mass extinction.2 Volcanism indeed makes an attractive rival to the Alvarez theory, as it is the only process other than impact that meets the dual criteria of being lethal and global. Furthermore, volcanoes erupt today and it is easy to project their effects backward in time. In conformity with Hutton's teachings, present volcanic activity might well be the key to past extinction.

In 1978, Dewey McLean of Virginia Tech proposed that the carbon dioxide accumulations at the end of the Cretaceous had caused changes in oceanic circulation and global climate (perhaps a kind of greenhouse effect) that in turn led to the mass extinction.3 In 1985, Officer and Drake adopted and refined these arguments, claiming that the iridium, shocked minerals, and spherules found at the K-T boundary are more likely to have been formed by volcanism than by impact.4 Although a single volcanic eruption can be almost as sudden as impact—witness the explosion of Mount St. Helens in 1980—it takes hundreds of such eruptions spread over hundreds of thousands or millions of years to build up a volcanic cone. If Officer and Drake are correct that the supposed impact markers can be produced by volcanism, the alleged spread of the markers for several meters above and below the K-T boundary would then be naturally

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