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No. 115: Jan-Feb 1998

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A SUBMARINE ORGAN?

Exactly two years ago, we reported on strange seismic signals detected by German geophysicists near Mount Semeru, in Java. These signals consisted of a fundamental tone and evenly spaced harmonics. Sometimes, the fundamental tone rose and fell. This "natural trombone" was thought to be a gas-filled subterranean cavity capped at the top by rock, with a pool of magma at the bottom. Volcanic vibrations resonated in this chamber. As the magma pool rose and fell, the fundamental tone changed.

More recently, a network of seismic stations in French Polynesia has picked up more mysterious seismic signals. These differ from those in Java in that each fundamental tone is "pure"; that is, there are no harmonics. Dubbed "T-waves," the sounds originated from an active volcanic ridge in the South Pacific. Suspicion fell on one flat-topped volcano that rose to within 130 meters of the ocean surface. But, how could this peak generate such a pure tone?

The theory is that the active volcano spews out a column of steam bubbles bounded at the bottom by the flat volcano and by the ocean at the top. Computer simulations proved that sound could resonate in a column of bubbles just as it does in an organ pipe. Since the height of the column remains fixed, so does the fundamental tone. Certainly harmonics are generated, too, but the bubbles damp out the higher frequencies, leaving a pure tone.

(Schneider, David: "A Blue Note," Sci entific American, 277:18, August 1997.)

Comments. The resonating-bubble-cloud theory was proposed in a 1996 issue of the Bulletin of the Seismological Society of America.

From Science Frontiers #115, JAN-FEB 1998. 1998-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "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