VOLCANIC ACTIVITY

Dominion, Volume 37, Issue 197, 18 May 1944, Page 3

VOLCANIC ACTIVITY

Geographical Society

Lecture

“Of all the large cities in Australia or New Zealand. Wellington is the furthest removed from all evidences of volcanic activity in the parft or in recent times,” said Dr. P. Marshall, Lower Hutt, in a lecture on the subject of volcanoes, given last night to the Wellington branch of the New Zealand Geographical Society. Dr. Marshall is consulting geologist to the, Public Works Department, and was formerly professor of geology at Otago University. His lecture was illustrated by lantern slides and moving pictures. There was a large attendance. Dr. Marshall said that there was no evidence of volcanic activity nearer. to Wellington than Ruapehu. In a recent book it had been stated that Wellington Harbour was a tremendous volcanic centre, as was proved by the fact that earthquakes were still experienced in it. “For a concentration of untruthful remarks it is hard to beat that,” said* Dr. Marshall. Volcanic activity did cause an earth trbmor.,but no earthquakes in the usual sense of the word, he said. Volcanoes were fouud here, there and everywhere in the Auckland district, and there was an extensive volcanic system on Banks Peninsula and another in Otago. Discussing volcanoes in general, the speaker said that they were one of the means of communication between the molten- interior of the earth and its surface. Only the upper two or three miles of the earth crust, he added, was cool enough to enable life to exist He showed pictures of various types of volcanoes aud volcanic rock formations. Among the latter were columnar rock formations found extensively in the Taupo district. These were formed by showers of minute particles, carried in a molten state in their own incandescent atmosphere. The particles, being molten, stuck together as they fell, and as the mass cooled, contraction caused vertical divisions.

Dr. Marshall also explained the origin of the conical mounds of volcanic debris found on the sides of Mt. Egmout. Volcanic lava streams, he said, generally moved slowly, and it was possible to Watch them with safety at close quarters. In Hawaii, however, they sometimes travelled at a speed of up to 10 miles an hour. In a more dangerous category were burning clouds from volcanoes, which travelled at speeds of up to 360 miles an hour. Among the pictures were some illustrating the results of the Tarawera eruption in 1885. The sound of that eruption, he said, was heard in Wanganui. 150 miles away, carried by earthwave, not airwave.

Other pictures showed -Ngauruhoe in the days of its activity. Dr. Marshall said that about 15 years ago it had become, for tbe time being, practically extinct. He added, however, that it was difficult to say when volcanic activity had ceased and when it had merely been temporarily interrupted. A resumption of Activity might yet be seen at Ngatiruhoe.