Tidal Waves 1925
A STUDY OF TIDAL-WAVES by Professor Vaillaux, a French authority, is given in The World’s Health, the organ of the International Red Cross (Paris). Says this writer:
The determination of the causes of this phenomenon, which often produces terrible loss of life and property, is especially difficult in view of the difficulties of observation. Testimony of witnesses who have escaped from the calamity is natuÂrally confused or contradictory. The seismograph and the barometer are the only instruments of value for scientific records, and the former can not function, of course, when earth tremors are absent.Â Observations from boats at sea are almost always useless because of the relatively calm rise and fall of the ocean-level as the tidal-wave passes. The problem is further complicated by the confused terminology of description. Finally, the frequent minor oscillations of the ocean-level, aside from the daily tide fluctuations, need to be recorded and studied for the same reason that a record and analysis of the 30,000 annual minor earth tremors are as necessary in the work of the seismologist as that of the thirty or forty great earthquakes. The problem is of the greatest interest to the warmer, volcanically unstable, regions of the globe, and is confined for the most part between latitudes of 40 degrees north and south.
“A resume is presented describing about twelve of the most destructive waves about which records are available.Â The scientific value of the reports on the Chilean wave of 1835 is of great interest, having been made by Darwin and Fitz-Roy, who happened to be on that coast at the time. One curious fact that these observers noted was that great flocks of birds flew in from sea more than an hour before the disaster ocÂcurred. The ocean first withdrew, leaving ships, which had been anÂchored at a depth of seven fathoms, on dry land; this action was succeeded by a wall of water thirty feet higher than high-tide level; then came a higher wave, and finally a still higher wave.
“The records in genÂeral show that when the first wave is positive, it is almost invariably followed by a wave or waves of greater height and force. Frequently, tidal-waves are not preÂceded by a negative undulation. South American populations, however, disregard warnings to flee until the ocean has first retreated. Much avoidable loss of life has occurred as a conÂsequence.
“Other waves occur which are not of eruptive or seismic derivation. The Bay of Bengal particularly is subjected to waves produced by atmospheric depressions combined with winds of a cyclonic nature, possibly coinciding with exceptionally high tides. Tide-rips occur also and spread ruin. They are quite frequent on the western coast of France.”