VOLCANOES & VOLCANOLOGY

Evening Star, Issue 17368, 2 June 1920, Page 7

VOLCANOES & VOLCANOLOGY

—■ —♦- LECTURE BY DR T. A. JAGGAR, Tho large number who gathered last mght to hear the address of Dr T. A. Jaggar, of Honolulu, shows the increasing popularity of the lectures under the auspicas of the University and Otago Institute. The lecture was held in the Y.M.C.A. Assembly Hall, 'and the audience included a number of ladies. 1 Dr Fulton, in introducing the speaker. ; mentioned that Dr Jaggar was stationed a>t the Hawaiian Islands, which were almost entirely volcanic, for the purpose of I conducting systematic observations and ! experiments. 'The lecturer-, in beghming, emphasised the need for study and physical experiment in volcanic areas, especially from the point of view of the welfare of humanity, so that ominous signs which almost always preceded volcanic eruption could be accurately interpreted and tho people in danger warned. In the caae of the. eruption of Mont Pelee, on the island of Martinique, when the' town of St Pierre and 40,000 of- the inhabitants .had been destroyed, earthquakes and rnrriI Mings had foretold the catastrophe,'but ! lack of scientific knowledge had prevented j their warning being heeded. At Dr Jag- : gar's volcanic observatory particular atj tent-ion was being paid to the volcanoes'of j Kilauea and Manna Loa. Tho seismograph recorded the earth movements, and j these records, combined with the observations of lava movements and temperaI tares, gave grounds for fairly accurate prej diction of volcanic disturbances. The rise and. fall of the lava levels in the mountains ot Kilauea and Mauna Loa was such that they had a definite belief that the two i-craters were connected b.- an underground j channel. Data for this* belief was verv j abundant, but showed that the connection , was not hydraulic. The belief that watervapor controlled volcanic movement was now being undermined. Clear connection I was now established between earth' tilts ;and surface movement on one hand, and ] the rise or fall of lava on the other hand. j Earth tilts generally preceded alterations lin lava levels by about three weeks. The sudden volcanic eruptions of volcanoes ,were due to the trigger-like release of ! underground gas under great pressure. Dr Jaggar bejieved that the crux of the mat|ter lay in the study and analysis of the j volcanic gases. He advocated the use of the spectrum and camera in the analysis jof the gases. The present method of obj taming these gases from the lava pits was j a rather dangerous one. When one had I chosen a suitable time when the pit was evenly crusted over, he advanced to the I centre of it, and, making a small hole, ! placed a vacuum tube over it. thus collecting the gas. The gases usually found were hydrogen, nitrogen, and the oxide? of carbon and sulphur: but they varied greatly in different volcanic areas. If a monthly record was published of the various tiltings. earthquakes, changes in temperature, and changes' ( in gases of tho chief volcanic centres of the world, this would ; be _of tremendous advantage to a science 1 which,_ though vitally important,'was yet in its infancy. j Dr Jack aiid Hon. G. M. Thomson eulo- ! gised the lecturer's excellent exposition of 1 the subject. ! Dr Jaggar, in the course of a brief rcplv, ' said that in regard to the human aspect the loss of life was not the only question. ,In the Bay of Plenty there was a possibility of a tidal wave arising and radiating from White Island, with this as its j centre. The case of White Island was ! almost, identical with that of other volI canoes that had erupted, in Japan espoj dally, and such an eruption, with the enjsume tidal wave, midit cause disastrous I results in the Bay of Plenty, which is ipopnlated by many thousands. Another I possibility in New- Zealand was that of j earthquakes. The activity of volcanoes I was generally ereat at intervals of 65 and j 130 years. All the large New Zealand ] towns had been built within the l.vt hun- | dred years, the movements of the volcanoes before that is unknown. Tho I coming of earthquakes to this coast was 'merely a matter of time. Although he j war. p>ised to see that the New Zealand i I buildings were li;;!,t, strong, and we!! j i fixed internally, cur eiurmocrs nii'st be I kept in touch, with volcanic activity and! j earthquake, record.*, and must build a tvpp ! j of building suitable tor a country subject ! ito earthquakes. ' j A number oi iiitercstinsr and valuable, slides on the -scientiric study of volcanoes were shown from a lantern operated bv Mr j Simpson. A number of charts shown 1 were of much assistance in followim; Uhe j trend of the observations and the conclu- ! a ion 3 arrived at. j Dr Jaggar received an enthusiastic vote of thanks at the conclusion of his address.