Home Page Science Frontiers

No. 8: Fall 1979

Issue Contents

Other pages

Other Interesting Sites











Iridium And Mass Extinctions

Alvarez and his colleagues at the University of California, while chemically analyzing a series of sedimentary strata from Italy, discovered that one layer had 25 times the concentration of iridium residing in adjacent strata. The iridium-rich layer forms the boundary between the Cretaceous and Tertiary periods, 65 million years ago. During that death-filled interval, 50% of the earth's genera were wiped out. Such are the two correlated facts: iridium increase and mass extinction. But do they have the same cause? Alvarez et al point out that iridium is rare on earth but much more common out in space. The anomalous concentration of iridium could have been injected by a massive solar flare, a big meteor impact, or come other extraterrestrial catastrophe. Thus is catastrophism being resurrected.

(Anonymous; "An Iridium Clue to the Dinosaur's Demise," New Scientist, 82: 798, 1979.)

From Science Frontiers #8, Fall 1979. 1979-2000 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