The Pamphlet Collection of Sir Robert Stout: Volume 68

III. Premonitory Indications of the Eruption

III. Premonitory Indications of the Eruption.

The eruption seems to have been preceded by few phenomena which can be considered as warnings of an impending outbreak. The eruptions of Vesuvius are frequently heralded by subterranean rumblings and earth-tremors, which gradually increase in frequency and violence until they culminate in the earthquake shocks attending the paroxysms of the eruption. But in the present instance no such warnings were given : the district around Tarawera was indeed visited during the months before the eruption by one or two small earthquake-shocks, but not more than was usual.

It seems, however, probable that the hot-springs at Rotomahana had shown a slightly increased degree of activity during the year or two preceding the eruption. At the top of the White Terrace was a geyser-basin of snow-white siliceous sinter about 90ft. in diameter. This was usually full of clear water of a deep-blue colour, the water in the centre boiling up violently to the height of 10ft. or 15ft. The basin commonly became dry whilst the south wind was blowing, but as soon as the wind changed it commenced to fill again. Captain Mair states that on these occasions, when the basin was almost full, "grand snow-white columns of boiling water, 20ft. in diameter are hurled 60ft. into the air." *

Mr. Josiah Martin was camping near the Terraces in November 1885, and was a witness of much grander eruptions of the White Terrace geyser. The first eruption was on the 22nd, and the second in the early morning of the 24th. On the second occasion water was thrown up in a column to the height of more than 150ft., accompanied by dense clouds of steam rising to 1,000ft. The Maoris stated that no eruption of such violence had ever been observed by them previously. (See Pl. p. 28.)

The magnitude of these eruptions may be regarded as furnishing some slight evidence that changes were then taking place underground near Rotomahana which were merely the prelude to the greater changes which eight or nine months later culminated in the eruption

Various other changes were noticed in the hot-springs of the Taupo zone during the months preceding the eruption, but, as such changes have been of more or less frequent occurrence ever since the springs have been observed, it would be unsafe to attach any special significance to them. It may however be noticed that the acid waters of the crater-lake on White Island disappeared about a year before; the eruption, leaving the bed of the crater dry.

When visiting Roto-elu (a lake fourteen miles north of Tarawera) in July, 1880, I found its waters some 4ft. below their usual level The Europeans living in the neighbourhood stated that the lowering of the water took place three months before the eruption.

A more certain sign of increased volcanic activity in the Taupo zone is perhaps afforded by the fact that steam was seen rising from the top of Ruapehu in the month of April preceding the eruption Mr. L. Cussen ascended the mountain on the 10th April, for the purpose of making trigonometrical observations. He states that the crater of Ruapehu contained a pool of water on that day, though the whole of the top of the mountain is covered with snow and ice. The water appeared to be steaming, and either gas or steam-bubbles were escaping at the surface. On the 16th of April he noticed a well-defined column of steam rising from the crater, several hundred feet above the mountain-top; it was visible several days subsequently. The Maoris said they had never known of such a thing before. On the 23rd of May the weather was very clear and bright, and a larger colums than usual ascended from the crater, about 300ft. above the mountain spreading out horizontally into a cloud-like mass.

Eruption of White Terracf.—22nd Nov 1885

Eruption of White Terracf.—22nd Nov 1885

From a Photograph by Mr J. Martin, F.G.S.

A party of tourists who visited Rotomahana on the 1st June (according to Sophia, the guide, and others, it was the 24th May), nine days before the eruption, stated that they had seen a kind of tidal wave on Lake Tarawera. On going down to the creek running into the lake, where the boats were kept, they found the creek dry. Then, with a rushing sound, the water came running up, quickly but gradually rising until it overflowed the creek. The water afterwards retired twice, coming back each time. The tidal wave was noticed also by the Natives at the Ariki. No mention is made of any earth-quake on this day; but it is possible that an earthquake shock on the further side of the lake, perhaps due to the Assuring of rocks underneath some part of Tarawera Mountain, may have originated a wave in the waters of the lake, and that this wave was greatly increased in height by the form of the arm of Lake Tarawera which stretches towards the Wairoa. This arm gradually narrows after the manner of a funnel.

The guides to Rotomahana state that the hot-springs and steam-holes were much more active just before the eruption, especially on the Tuesday, two days before, when several holes which had been quiet for years were pouring out large volumes of superheated steam, But, although the statement is not improbable, and is indeed confirmed in part by the accounts of visitors, it is clear that much stress cannot be laid upon it.

* Trans. N.Z. Inst., Vol. IX., p. 27.

Trans. N.Z. Inst., Vol. XIX., p. 377.