“Tidal” Waves.

Hokitika Guardian, 5 January 1923, Page 4

“Tidal” Waves.

fßy Cajit. A. A. Bostic. Mercantile Marine). The uncanny behaviour of the sea which invariably accompanies an earthquake is enough to .strike terror into . the heart of the bravest—even the! hardened sajilor familiar with me ■ ocean in all her moods. I The first intimation of the arrival of • the terrible “tidal wave” is the recce j iug of tin sea from the shore. This • recession varies;: sometimes it may I. only thirty or forty feet ; at other timi it has been known to bo more than a , mile. | The time which the dreaded si a ■ wave takes to arrive after the reeesinu also varies. It. may take half an hour or more, or it may overwhelm the unfortunate inhabitants in the coast towns in the course of a f< w minutes. Various theories have been given in explanation. One is that is an earth wave on tin ocean lied which, lrav«; ling inland, carries a forced sea wave with it. As it reaches higher ground ; the sen wave slips oil. thus causing the withdrawal. Then, reinforced by the enormous submarine disturbance and the water it has accumulated by sliding hack, it hurls itself forward wit.!; great destructiveness. There is another theory that tieearthquake lapses huge submarine ’ landslides, and that thn vast displace monl sets the ocean in a state of ex ; (•illation. As a fact, there are usually , marked changes in the diplh el water; afterwards. A not unlikely explanation is that the waler finds its way down fissure 1 In the underlying heat-oil locks, and. turning into steam, causes the wave, which is moio dreaded on shore than the nurtliquake itself. From various records one discovers that the majority of these waves do not usually exceed about 80 or 90 i'e< t in height, but tin* seventy foot wave which swipt Lisbon alter the earthquake in 17. Vi was sufficiently destructive to drown .">O.OOO people. This height, however, is by-no means (he limit, for in 1737 a. wave which broke near ('ape l.opatka was estimated to have reached a height of 210 it. One sea captain has left on record an ex penciled which few men can boast. In the year ISlti .when lie was oil llm island of RarnUmga, in the Pacific, an appalling storm aniu.se. and a tremendous wave swepi the island, carrying all before it. Catching his slop upon iis course, il carried her far inland. Nobody ever measured this wave. \ but the captain afterwards stateil that he could feel the palm trees grating against the keel of his vessel.