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Mount Ruapehu

By R. L. Oliver

What are volcanoes? Live ones, I mean. Are they angry Gods chiding children for their sins, or are they reflections of the devilish flames of hell itself? Or instead, are they the surface manifestation of an earth's accumulated store of radio-active heat? They're certainly healthy things, whatever they are, and Mt. Ruapehu is no exception.

Sadly enough, we New Zealanders inhabit a very unstable part of the earth's surface, and share this misfortune with (among others) a lot of unfortunates living on the shores of the Pacific Ocean—on the so-called "Girdle of Fire." There are other rather shaky parts of the earth's crust, and occasionally the world mourns the loss of a community buried beneath the exudations from a volcano. But man accepts such incidents imperturbed. Villages flourish on the slopes of Mt. Vesuvius, which mountain once destroyed a city; villages are scattered throughout the very active region which recently produced the Mexican Paracutin; and Hawaiians are unmoved by the threat of lava flows from Kilauea or Mauna Loa.

It is a peculiar trait of man, this—the stoical indifference to danger. Or is it rather a manifestation of the gambling spirit—possibly an eruption, but more likely not—combined with a certain laziness, namely a disinclination to disturb the happy home because of a mere potential danger? How true is the maxim "Familiarity breeds contempt."

It must be remembered, of course, that there are volcanoes and volcanoes. Some explode violently. Some exude treacly flows of lava, but don't explode. From others may flow a more viscous rubbly lava, and such flows may alternate with explosive eruptions. Strangely enough, a particular kind of activity usually persists—a volcano is either one type or another, and remains so.

Thus, the risk involved in being on or near a volcano is relative. For years, scientists have played about on the summit of Mauna Loa and Kilauea, the active Hawaian volcanoes, observing the activity at close quarters. They know the danger from an explosive eruption is almost non-existent, and that, if the activity is at a particular stage, the possibility of there being an overflow of lava is slight.

But most other types of volcano are potentially explosive, though the explosions do not necessarily blow away the mountain's summit. Many, such as Ruapehu, are in the habit of exuding lava in the form of domes, or tholoids, while outbursts of varying intensity from vents in the tholoid spread debris over the surrounding countryside. Eventually, activity ceases, and the tholoid is left standing; or perhaps, explosions have blown all or part of it away. And again perhaps, the tholoid as a viscous rubbly lava flow may crawl a little way down the mountain-side.

What will be Ruapehu's fate? The inhabitants of the neighbourhood wait in trepidation.

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