NGAURUHOE.

Otago Daily Times, Issue 17158, 10 November 1917, Page 10

NGAURUHOE.

NATURAL SAFETY VALVE.

The present eruption of Ngauruhoe J stated by Professor A. P. W. Thomas, who, until his retirement from active work, was professor of geology at the Auckland University College, to represent the first instance of an overflow of molten matter from the crater since 1889. Professor Thomas made a survey of the Tongariro volcanio system in 1887, shortly after the Tarawera eruption, and then examined a stream of lava which had poured down the north side of Ngauruhoe in the 1869 outbreak into the south crater of Tongariro. A sample of the solidified flow of last week, which was taken to Auckland by the Herald representative who slopt on the mountain on Friday week, was pronounced by Professor Thomas to be of the same general character as the lava of the 1869 overflow.

Ngauruhoo is described by Professor Thomas as the dominant vent of the Tongariro volcanic system, and the only cone of tho eeries from which lava has been ej-eefcod within the memory of living man. At various periods in the last 30 years the volcano has displayed activity to the extent of emitting steam clouds and showers of stones, and changes have been reported from time to time in the outline of the top of the cone. These, however, until now, have been the only manifestations of the power of the mighty subterranean forces. Tongariro has not been known to show activity during the historic period. The only active points in the group for some time past, other than Ngauruhoe itself, have been:—(l) The Red Craiter, to the north-east of tho mountain, which had ejected stones shortly before Professor Thomas's inspection in 1887, and has sinco shown similar activity at intervals; (2) the steaming pools of Te Meri, still further to the north-east; and (3) Ketetabi, a similar pool on the northern side of the group. As to the deductions to be made from the present eruption, Professor Thomas remarked that while it is rash to make any prediction as to the probable action 1 of any volcano, still while Ngauruhoe shows a fairly free vent, as at present, it may reasonably be regarded as.a kind of safety valve to the pont-up subterranean forces in its neighbourhood. The present startling phenomena imply the existence of pent-up forces, and it is reassuring to know that a vent is provided for them, inasmuch as they are the less likely to accumulate such pressure as would lead to an explosion in some other direction.