SEISMIC ACTIVITY

Dominion, Volume 16, Issue 102, 16 January 1923, Page 6

SEISMIC ACTIVITY

RECENT EARTHQUAKES AND VOLCANIC ERUPTIONS In tho course of a short address on “Recent Earthquakes in New Zealand,” Dr. C. E. Adams, Government Astronomer, stated that records of the earthquakes were obtained from about eighty postmasters and others whose stations were distributed throughout tho Dominion. The most severe earthquake in 1921 was that of June 29, which had a intensity of 8 on the Rossi-Forel scale. Its centre was near Gisborne. The Taupo earthquakes, beginning in Juno, have not vet, he said, entirelv subsided. The earthquake of December 25 had its centre in the Cheviot district, and had an intensity of 9. ns shown in the Rossi-Forel scale. The highest intensity on this scale was 10. . Eruptions in New Zealand Area, Dr. J. A. Thomson, Director of tho Dominion Museum, delivered an address on “Eruptions in the New Zealand-Tonga Volcanic Belt.” Ho said that the late Mr. Percy Smith had given an excellent account of the Tarawera eruption, and that nearly all that was known of the volcanic eruptions in tho Kormadec Islands had been recorded by him. Ruapehu appeared to be an extinct volcano, but the lake at its summit had been violently disturbed on several occasions, and steam had been seen rising from it. No lava had boon erupted from the actual crater of Ngauruhoe, but Air. Biilwill stated that on one occasion some lava flowed from a vent on its side. There had been many explosive eruptions, and flames might have accompanied some of tlilese. There had., said the lecturer, been several eruptions of vents on TongarirnTe Maire and Red Crater. Friedlander had described one of these, which was accompanied bv flames of different colours. Tho eruption of Tarawera on June 10 1886. took everyone by surprise, but in tho light of present knowledge there were a number of signs of the coming eruption. The geysers and hot springs of the district were more active than usual. Small masses of Inva seemed to have welled up in some of t.hg lesser craters along the Tarawera r'ft. In 1900 the Wainnngu Geiser began to h plnv from one of the small craiers along Ihe. Tarawera rift. In 1917 Frying Kan Flat blew out .and destroyed the AVaimnngu vent.. It seemed to have been a true eruption. At AATiite Island, in September. 1914, a tragedy occurred, all the sulphur workers on the island losing their lives. Only u ent was saved. Eruptions on Sundry Island, in the Kemindoc Group, ru-ourred in 1814, 1872, 1886, nnd in 1902. Active Tonga-New Zealand Belt.

The speaker said flint there were ten volcanic vents :n the Tonga Islands. There were oulv three actual volcanoes on tho lane., flio others were submarine. Many eruptions had been recorded. This volcanic belt from New Zealand to Tonga was evidently a very active one, and systematic records and observations wee highly desirable. The lecturer emphasised the need for a volcano observntorv, and mentioned that eruptions could bo predicted, ns hed’hoen done bv Dr. T. A. Jnggnr in Hawaii. He also mentioned that in Japan a serious oruniion was n'-edicted a fortnight before it occurred. The neighbouring population ’.s removed, and no lives were lost. With out present knowledge. Dr. Thomson said that ho firmly bcliei’od that the Tarawera eruntion— ; its t'me and nlnce—could have been predicted, and thus lives which had been lost could have been saved. The Taupo 'Quakes. In tho course of a brief address on “The TaujX) Earthquakes of 1922,” Professor E. Marsden, D.Sc., remarked that these earthquakes, which began in June, 1922, were still continuing, but were now very slight. Tho ’quakes had been felt as far west as Taumarunui. A few miles west of Taupo township a large block of land on the north shore of the lake had dropped nine feet. The fall diniinished in the north and petered out eight or nine miles in that direction. Tho fall had taken place over a period of several months. It was not known, he added, how far, the fallen block extended under Lake Taupo. No evidence of it was seen at Tokaanu.'at the south end. A post had been put in the lake, so that any further movement of the block might he observed. Home-made seis; mographs were installed at AA'airakei and Taupo. Tho actual records were disappointing, but very informative as to what should be done in the future. The cause of the earthquakes was undoubtedly actonic —that was, dependent on movements of the earth’s crust, and not volcanic, or duo to subterranean explosions of any kind. The tremors were very frequent during tho early part of the period over which observations were made—up to 20 or 30 in an hour. Their intensity on the RossiForel scale was from 1 to 6—l being a tremor imperceptible to the senses, and 6 a somewhat violent.shake. No great material damage was done. Many of tho tremors were accompanied bv rumblings and curious noises. Yolcanological Data. In a subsequent discussion on the advisability of establishing a volcanological and seismol.og : cal observatory, Professor Marsden advocated the ni>uing of portable seismological instruments at Rotorua, and taking then., if required, to any district where an earthquake had occurred. Tho after shocks would thus be recorded. A volcanologicaj observatory on the slopes of Tongariro was advocated bv Dr. J. A. Thomson and Professor Burb'deo. Professor L. A. Gotten said that AVellington was not likely to be free for all time from ea.rthouakc shocks, and he therefore urged the fuller equipment of the AVellington t.bsqrvatory Hie meeting passed a resolution recommending the establishment of a yolcanological observatory, nnd additions to'The instruments at AVellington.