EARTHQUAKES CAN BE FORETOLD

Rotorua Morning Post, Issue 5320, 5 February 1947, Page 3

EARTHQUAKES CAN BE FORETOLD

• AD&RESS TO ROTARY CLUB BY MR. J. HEAiLEY. The geological history of New Zealand, with special reference to the volianis and thermal areas, was sketched in broa.d outline by Mr. J. Healey for Rotorua Rotarians at their weekly luncheon on Monday. The vulcanologist, apart from o.bserving the geological features of the land that could be seen, had to be a theorist of what went on beneath the surface. Contrary to the old idea that the earth was a cooling hody, said Mr. Healey, theie was evidenee that aithough we had a glacial period a mil^ion years ago, it had been preceded hy many such periods, and in betweqn there had been volcanic outbursts that showed that insofar as the surface was concerned, there \vas 110 diminution of heat. From 100 to 300 million years .ago, New Zealand was under the sea; then thousands of feet of sandstone strata and shale had hardened by pressure, folded, and parts were thiuist up, to "form the backbone of the eountry. The eastern part of the Rangitoto Ranges, the areas round Kawhia, and between Taupo and Napier were part of this aneient structure, which 50 million years ago sank again beneath the sea. Whether the Rotorua area was a section of the older formation we did not know. 1 From 10,000 to 15,000 square miles of volcanic rock had been preeipitated out of the earth. The theory was that this rhylotic rock was extruded from a fracture in the earth's surface, the hot gases acting as a .lubricant, just as water acted as a lubricant in landslides. Some of these areas of molten rock had flowed distanees of 50 to 100 miles. One bed, 500 feet thick, might 'have emerged in an hour or two. The New Zealand type of earthquake, which originated 120 to (150 miles below the earth's surface, had parallels in many other parts of the world. Consequently, the study of their features was useful throughout the whole Paeific region. • We could tell much more about &ubsurface conditions than fonnerly, and the seismograph had helped greatly m the assembling- of scientific .lata. Had these been available at the time of the Tarawera eruption, eertain seismic disturbances, which always preceded a great outburst, co-uld have been detected and the eruption predicted. A vote of thanks to Mr. Healey, moved by Mr. G. H. Beale, was carried by acelamation.