NOT WORRIED ABOUT TSUNAMIS

Press, Volume CIII, Issue 30469, 17 June 1964, Page 3

NOT WORRIED ABOUT TSUNAMIS

(N.Z. Press Association) AUCKLAND, June 16. The danger to New Zealand from tsunamis from distant sources was not considered to be great, said Mr B. N. Thompson, of the Department of Scientific and Industrial Research, at Whenuapi today. They had caused little damage in New Zealand, he said. In a paper on the natural hazards facing New Zealand, he told the northern region civil defence course that the Pacific Ocean was prone to tsunamis, but more so in the north than the south. Tsunamis, sometimes 100

miles in length, two feet high and travelling at 300 to 500 miles an hour, and caused by submarine earthquakes and volcanic eruptions, arrived at the New Zealand coastline at irregular intervals. Generally not- noticed by ships, their course was plotted by an ocean-wide warning service. The danger from them would appear to come from earthquakes centred a short distance from the shore, he said. They had caused little damage here. In 1868, a person was drowned in the Chatham Islands and in 1947 a tsunami swept through a hotel and cottages north of Gisborne. A tsunami from the Chilean earthquake in 1960 reached New Zealand, where sheep-

dogs chained in kennels on the Bay of Plenty coast were carried out to sea and drowned. Near the Auckland harbour, a stretch of water eight feet deep drained away and returned as boiling surface A study of the pattern of volcanic activity in the North Island over the last 25 million years had been made. This led to the conclusion that further eruptions could be expected in the Auckland area, said Mr Thompson. The youthfulness bf Auckland’s volcanoes was shown by the uneroded shapes and the weakness of weathering of rocks. ' This had been confirmed by radio-carbon dating. Rangitoto was active 760 years ago. Mount Wellington 9000,

Mapgere about 15;000, Three Kings 21,000 and Wiri about 25,000 years ago. There were at- least 50 separate centres within 250 miles of the Auckland field and the statistical average of time between spasms of eruption would be about 4000 years. > The probability of renewal of activity was about 2 per cent in any one century. There was no way of- predicting the locality of the next eruption in the Auckland city area because there was no clear pattern of distribution of activity according to age; nor any tendency to shift across the field, said Mr Thompson. No part of the land around New Zealand could be regarded as free from earthquakes.