RUAPEHU DANGER

Grey River Argus, 8 September 1945, Page 3

RUAPEHU DANGER

BIG OUTBURST To be Guarded Against PA WELLINGTON, Sept. 7. ’ Mr. H. E. Fyfe, Field Geologist on the staff of the Geological Survey, in a preliminary report on his observations at Mount Ruapehu during August, pointed out that, so far, the siesmic activity preceding the present eruption had not been investgiatea. He continued: “It is rather important that this should be done to decide whether the activity derives from' some deep-seated source, or is merely from the reheating of a residual pocket of Magma, left from some previous outburst.” Mr. Fyfe added that so little was definitely known of the actual mechanism of volcanoes that it was rather difficult to predict the future course of Mr. Ruapehu’s activity. From the copious steam emitted, it was reasonable to assume that, on the other hand, the cooling effect of the rapidly expanding steam and gas was likely to maintain a viscous, or semisolid Dlug in the conduit, and so to control the course of the eruption. The balance between the rigidity of this plug and the evolution of the steam lower in the conduit would determine the violence of the explosive outbursts. The steam pressure might build up sufficiently to shatter the crater walls, and, in such a case, it was likely that the violence of such an outburst would be directed towards the Wangaehu side, the weakest part of the crater rim. The violent steam explosions were, however, usually caused by sub-surface water reaching some part of the lava column. and at the present stage that possibility was not entertained, though, in the drying phases of present eruption, surface water might find its way into the top of the lava column.

Mr. Fyfe considered that such a steam explosion was improbable. It could not be assumed that the activity in the Tongariro-Ruapehu zone was dying or dead. It had been merely dormant. The magma was rich in volatiles, chiefly water, and if the magma was deep-seated, the present activity might be controlled by physical conditions in the conduit restricting and controlling the reactions in the upper levels of the lava column. With the removal of any construction in the vent, more violent phases of eruptite activity might ensue. The structural set-up and the deep-seated fault complex, extending from the Bay of Plenty to Ruapehu, along which there had been profound volcanic activity in times past, was ideal for repeated disastrous outbursts. Sooner or later they would eventuate. BIG SOUTH PACIFIC ’QUAKES.

(Rec. 5.5.) N'EW YORK, Sept. 6. Several seismographs have recorded two strong earthquakes, apparently in the Netherlands East Indies or in the South Pacific.