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No. 31: Jan-Feb 1984

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Wanted: disasters with a 26-million-year period

J. Sepkoskiand and D. Raup, two researchers at the University of Chicago, have drawn up graphs showing the numbers of families of marine organisms that have vanished from the fossil rec ord over the eons. From this overview of manifest mass extinction emerged a puzzling and potentially profound pattern. Roughly every 26 million years over the last 250 million years, the number of extinctions jumped well above the background level. Some cyclic phenomenon seems to have been killing off life forms on a systematic basis. But no natural 26-million-year cycles are known although meteors and comets are favored causes of mass extinctions these days, they display no such cyclic period.

(Simon, C.; "Pattern in Mass Extinctions," Science News, 124:212, 1983.)

Comment. Instead of looking outward to astronomical catastrophism, perhaps we should look inward. The earth itself may undergo cyclic paroxysms; or life might undergo intrinsic phases of decline and rejuvenation.

Major extinction events in the evolutionary time scale
Periodic events in the evolutionary time scale. The 300-million-year cycle shown involves alternations between "icehouse" conditions (O) and "greenhouse" conditions (G). These may be due to changes in heat convention within the earth.

From Science Frontiers #31, JAN-FEB 1984. 1984-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987