Contingency plans for big eruptions

Press, 10 November 1980, Page 28

Contingency plans for big eruptions

Recent volcanic eruptions at Mount St Helens in the United States have prompted New Zealand Civil Defence officials to consider contingency plans for mass movement of people in case of a big eruption. The National Civic Defence Planning Committee on Volcanic Hazards held its first meeting on September 30, and will meet again this month to consider its terms of reference and submit initial reports. It includes representatives of the Ministry of Works and Development, the Department of Scientific and Industrial Research, the police, the Post Office, and the Ministry of Civil Defence. Statistically, the chance of a volcanic eruption in New Zealand is increasing, according to the assistant national director of the Ministry of Civil Defence (Mr J. M. Flavell).The Mount. St Helens eruption, and the eruption of the long-dor-mant Mount Lamington volcano in Papua New

Guinea, underlined the fact that “dormant” volcanoes were never dead, Mr Flavell said. Mount Lamington was quiet for 1000 years before its eruption in 1950, killing 4000 people. Auckland was surrounded by 60 supposedly “extinct” volcanoes, but it was only 200 years ago when Rangitoto last "puffed.” It was only a small event, but it showed that volcanic activity there was still possible. Mount Egmont in Taranaki was supposedly “dormant,” with 600 years since its last volcanic activity. Mr Flavell said mountains such as Ruaehu, Tongariro, and Ngauruhoe. White Island and the “ever-present signs of volcanic activity round Rbtorua” posed more obvious threats. Recent activity at White Island was greater than ever before in historic times, Mr Flavell said.

"Not too much comfort should be taken from the fact that activity has waned slightly in the last month or two; previous reductions in volcanic activity have been followed by eruption sequences.” If a big eruption occurred there, the effect could be something like the power of an atomic bomb — and White Island was only about 50km from the Bay of Plenty coast, he said.

The danger of such an eruption would not necessarily be the amount of material blasted on to New Zealand. The main danger would be from tidal waves.

If that happened, the minimum warning time for evacuation to high ground might be 15 minutes, illustrating the need for a vigilant observation service, and plans for mass movement of people before the event, Mr Flayell said.

However, there were few areas in New Zealand which would explosively erupt without warning.

Such eruptions would in most cases be preceded by noticeable build-ups for some months. Scientists seemed fairly confident they could predict eruptions anywhere in New Zealand, he said. “Dormant” volcanoes also existed in the sea off the coast of Taranaki, north-west of Mount Egmont.

Scientists were “pretty certain” that any past volcanic activity in the South Island was now extinct. The curator of geology at the Canterbury Museum, Ms Margaret Bradshaw, said the last evidence of eruption of the Banks Peninsula volcano had been dated at between five and seven million years. “The chances of an eruption in the South Island are very remote,” she said. New Zealand building codes specified earthquake resistance requirements. Mr Flavell said houses in high volcanic-risk areas might have to be built with steeply pitched roofs in future, to prevent dangerous build-ups of volcanic ash if an eruption did occur. The "New Zealand Journal of Geology and Geophysics” has warned that further eruptions in the Auckland field must be expected. It predicts that any future eruptions will occur within the boundaries of the present field, and that any outbreak is more likely at a new site within that field. Volcanic eruptions differed from other civil defence emergencies in the time involved. In a flood, people could often return to their homes after 24 hours.’ After a volcanic eruption, resettlement could take years — if ever, Mr Flavell said. The. committee and the precautions being considered should not be viewed as “alarmist proposals,” he said.

“But emulating the ostrich does not do anybody any good.”