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No. 87: May-Jun 1993

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Whence the earth's pulse?

Geological history records a restless planet subject to a succession of chemical and physical upheavals. Have these great paroxysms been random in time? M.R. Rampino and K. Caldeira do not think so:

Number of geological events during geologic time
Number of geological events during geologic time

"Published data sets of major geologic events of the past 250 Myr (extinction events, sea-level lows, continental flood-basalt eruptions, mountain-building events, abrupt changes in sea-floor spreading, ocean-anoxic and blackshale events and the largest evaporite deposits) have been synthesized (with estimated errors). These events show evidence for a statistically significant periodic component with an underlying periodicity, formally equal to 26.6 Myr, and a recent maximum, close to the present time. The cycle may not be strictly periodic, but a periodicity of 30 Myr is robust to probable errors in dating of the geologic events."

The obvious question is: What could cause a 30-million-year periodicity? Internally, the earth's innards might be periodic, possibly in terms of plume eruption, mineral phase changes, core convection, etc. Externally, comets and asteroids are cyclic. Rampino and Caldeira point out that the solar system crosses the heavily populated plane of the Galaxy every 30 million years.

(Rampino, Michael R., and Caldeira, Ken; "Major Episodes of Geologic Change: Correlations, Time Structure and Possible Causes," Earth and Planetary Sci ence Letters, 114:215, 1993.)

Reference. We catalog crater periodicity in ETC4 in Carolina Bays, Mima Mounds. This catalog described here.

From Science Frontiers #87, MAY-JUN 1993. 1993-2000 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