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The Pamphlet Collection of Sir Robert Stout: Volume 67

Sympathetic Action in Neighbouring Areas

Sympathetic Action in Neighbouring Areas.

An attempt has been made in the foregoing pages to show that the recent eruption occurred on a line of one of the great fissures of the earth's crust: a necessary corollary of this is that the action was deep-seated, and not local and superficial; consequently some signs of sympathetic action—either of a positive or negative order—might be expected in other parts of the great fissure, if not in those parallel ones which have been described. The following notes of occurrences which took place simultaneously or shortly after the outburst tend to show that such sympathy of action does probably exist. It is true that a few of these symptoms may be due in some measure to fractures of the underlying but more superficial rock-masses induced by the frequent earthquakes, but not wholly so, or otherwise similar occurrences would have been noted at the times of former earthquakes which equalled in severity those at the time of eruption.

Although it was reported by a road-party encamped at Poutu, just under the foot of Tongariro Mountain, that they were aroused on the early morning of the 10th by hearing a loud rumbling noise in the mountain, accompanied by louder detonations like the reports of cannon, and that lightning was playing round the summit of the mountain all the time and up to daylight, and that every moment an eruption was expected; Major Scannell, residing at Taupo, neither saw nor heard anything of it. He says: "I was up during the severest part of the eruption, that is to say, from half-past 2 to 5 a.m. I thought on first waking that the sounds I heard came from Ngauruhoe, and went round to look at it. The moon had set behind our western chain of hills, but there was sufficient light left to dis- page 36 cern the snow-capped summits of Ruapehu and Tongariro—they stood out plainly from the clear starlit sky behind: they were perfectly quiet, and there was no cloud, no lightning, nor any sign of disturbance, either volcanic or elemental. During the two and a half hours I was watching the eruption I saw the mountains at least twenty times, and there was no change whatever, nor any when viewed through the glass at 9 o'clock in the morning—nothing but the usual column of steam arising from the crater. . . . I took the temperature of some of the springs near here (Taupo) about three years ago, and kept the record by me; and again last week, the first day I could spare since the eruption, I did so again. With the exception of two or three at the Ruahine group, round the Crow's Nest, they were all colder. Those at the Ruahine, especially that known as the 'Witches' Caldron,' were much hotter; but, as I had taken them previously after heavy rain, I think the increase in temperature easily accounted for." Te Heuheu, living at Toka-anu, also reported the detonations which had been heard at Tongariro; but probably both he and the road-party were deceived by the reverberation of the noises from Tarawera echoing among the mountains. This is negative evidence, but never-theless valuable, as will be shown directly.

If we now pass to the northern end of the great fissure or volcanic belt, we find abundant evidence of great activity displayed in White Island, which has, indeed, continued for some months since the eruption.

Thursday, 10th June.—"White Island is apparently quiescent." "Te Puke settlers state that shortly after the outburst of Thursday morning a violent eruption took place at White Island. Masses of rock and volumes of steam were hurled into the air."

Friday, 11th.—"The 'Hinemoa,' which passed about midnight, reported no unusual activity." "The only alteration noticed by the 'Hinemoa' was a fresh steam-jet playing violently at the landing-place, and that all the gannets had left the island." "Captain Fair-child [on the 16th] stated that the island was slightly more active."

Saturday, 12th.—"Mr. West, mate of the 'Argyle,' when on watch late on the Saturday night off Cape Colville, with others saw a great glare of fire in the direction of White Island, and shortly after a ball of fire arose and immediately burst into numerous stars."

Sunday, 13th.—"'Te Anau' passed. Saw no unusual sign except that the island was enveloped in dense cloud." (This would be at night.) "A great cloud of steam seen arising all day" (from Rotorua).

Monday, 14th.—"A great cloud of steam seen arising all day from the Township of Rotorua." Tauranga: "During the whole of page 37 the day White Island could be seen discharging immense volumes of steam and smoke." "It is evident there is a violent outbreak at White Island to-day. From early morning there has been a vast cloud of steam and smoke arising and hanging over the island—almost as much as from Tarawera."

Tuesday, 15th.—Tauranga: "White Island continues in a very active state, and could be seen discharging volumes of steam this morning."

Ever since the eruption up to the time of writing, White Island has frequently been observed to be in a greater state of activity than usual, though not continuously so. On the 8th July it was reported "that during the last two days it has been unusually active, and large columns of steam have been rising from it." On the loth July Mr. J. B. Jackson observed from Oreti Point "that the cloud was very dense, and, instead of rising as steam does, it lay along the water in a northerly direction, there being at the time a light wind off the land, for a distance of nearly twenty miles, the angle subtended between centre of island and edge of cloud being 39° 22′. I have frequently observed that the crater has been extremely active since the eruption, and on several occasions have seen what I believe to be smoke issuing instead of steam." On another occasion Mr. Jackson measured roughly the elevation of the top of the column of vapour, and made it to be about 4,200ft.

Mr. C. Alma Baker, who visited the island on the 16th September, has been good enough to furnish the following notes: "The island, with the exception of two large rents or openings—the largest of which was our landing-place—forms a perfect crater with walls about 300ft. high, from the centre of which rises a grand column of steam to a height of about 15,000ft. On landing, a roaring, deafening sound could be heard, caused by the steam issuing from the vents at the far side of the crater. Numerous jets of steam were issuing from amongst the boulders at the landing-place. Here, and for some hundred yards inland, there was very little fresh deposit—indeed, all the buildings, tram-rails, &c., formerly used by the sulphur-workers at this spot were entirely free from it, although on the face of the cliff to the eastward, and, indeed, over the whole of the interior of the crater, there was a considerable deposit of fine mud similar to that at the Wairoa. After traversing about 200 yards over greyish, slippery mud, with numerous steaming sulphur-holes on every side, we came upon the vent which produced the noise. At the bottom of a depression about 30ft. deep, with a diameter of 100ft., were several fumaroles, from which issued steam at very high pressure, with a most page 38 deafening noise. The ground vibrated all around here for many yards. The deposit on the surface about this part was extremely curious, being composed of layers of various colours from white to black. At the west end of the depression, and close to its edge, it was very beautiful, an acre or more being covered with lovely white globules. To my surprise, I found that only a thin crust of about 6in. in depth formed the surface, whilst underneath a stick could be thrust down 4ft, or oft. into a whitish, soft, steaming mass something like the diatomaceous earth of Rotorua. This was in the bed of the former lake, which has entirely disappeared. Moving to the north-west for about 600 yards, and picking our way carefully along the side of the old lake-bed to avoid the many deep steaming fissures that rent the surface, we arrived at the edge of a depression about 100ft. deep, at the bottom of which lay a small lake of an indescribable milky-green hue, around which arose the forbidding black walls of the crater to a height of 300ft. From innumerable fissures in the walls large quantities of steam issued forth. At the north-east end of this lake, and raised about 3ft. above it, and immediately under the walls of the crater, was a very large steam-hole, from which issued with fearful uproar columns of reddish-brown and white steam, which rose to a height of many thousand feet. This red-coloured steam was mistaken for flame at some distance off. Strange to say, I found that the water of the lake was hardly warm, whereas from its proximity to the steam I had expected to find it nearly boiling. There evidently has been an eruption at no distant date, for mud can be seen in several places, even on top of the higher peaks of the hills outside the crater." Plate No. 2, drawn from a sketch by Mrs. Alma Baker, gives a good idea of the appearance of White Island as seen from the south-east.

Some of the "Hinemoa" people landed on the island on the 3rd September, and walked across the bed of the crater-lake, the water having disappeared. They found the principal scene of activity in the north-west portion, where steam-holes were fuming away at a great rate. The aspect of the island is changed to a considerable extent. It has been a matter of general notice by settlers living on the coast of the Bay of Plenty that the island has exhibited greater and more frequent signs of activity since the 10th June; but, evidently, from the statements quoted above, this activity has been of an intermittent character.

At Rotorua, the site of innumerable hot springs, situated on the most westerly of the three parallel fissures before referred to, a very great increase in action was noticed on the night of the eruption, page break
Plate No 2.

Plate No 2.

White Island

looking north-east-three miles distant.

From a sketch by Mrs. C. Alma Baker.

page 39 which still continues. The changes, indeed, are so remarkable that it is a matter of surprise that they should have been doubted. In numbers of places in and around the Maori village of Ohinemutu, and the Government township and sanatorium, hot springs burst forth from the ground in positions where none had been known before. Near the Government Agent's house a fine spring of boiling water, 10ft. in diameter, bubbles up to a height of several inches, whilst close by are smaller ones, from which flows away northwards to the lake a fine stream of hot water. From this spot northward, following round the foot of the Pukeroa Hill—the site of many hot springs in former days, as shown by the immense mass of siliceous sinter there deposited—steam escapes from the ground in numbers of places; whilst at others little springs of very hot or boiling water come to the surface, the water from which runs away to the lake. In the pa itself several fresh hot springs appeared—some in the floor of the great meeting-house called Tamatekapua—and many of the preexisting springs showed increased ebullition and temperature. Nearly all of these burst out on the night of the eruption.

The temperature of Rachel's bath at the sanatorium, whose normal heat is 170° Fahr., rose gradually during the twenty days following the eruption to 196° Fahr., at which it was recorded on the 1st July; whilst at the same time the volume of water was increased. In the beginning of August this spring was more active than the writer had ever seen it. At the same time the fine boiling spring from which the main supply for the swimming-bath is derived was exceedingly active, the water rising in great bubbles two or more feet above the surface. In several places over the plain on which the township stands steam escaped from vents long extinct, and at others it burst out in fresh localities.

Whakarewarewa, the Maori village situated about two miles south of Ohinemutu, has been known as the site of many active hot springs and geysers for as long as tradition goes back. Ever since the eruption these springs have been somewhat more active, but on the 25th June the boiling caldron in which the Maoris ordinarily cook their food—a place 20ft. in diameter, and to which no bottom can be seen through the clear waters—suddenly burst out into eruption, casting scalding water, stones, &c., around. This frightened the resident Maoris so much that they abandoned the village. About this time, also, the great geyser of Waikite, which had been entirely inactive for twelve years, suddenly came to life again and commenced playing, sending boiling water high into the air, accompanied by dense clouds of steam. At the end of July the Whakarewarewa geysers presented page 40 a most beautiful sight. There were generally three or four out of the five playing at the same time, and Waikite frequently sent the water up to 60ft. and 70ft. above the orifice from which it spouted.

At the time of the eruption the level of Rotorua Lake was observed to oscillate considerably, as the following notes, obtained bv Mr. Boscawen from the bath-keeper at the sanatorium, show. At 7 a.m. on the 10th it fell 1in., at 9 it rose 6in., at noon it fell 3in., on the night of the 11th it fell 5in., on the 12th it rose½in., and continued oscillating for some days afterwards. Up to the end of July the waters had risen—permanently, apparently—to 19in. above their ordinary level. A good deal of speculation has been indulged in as to whether this rise is permanent, and also as to whether the lake-shore near Ohinemutu has not subsided. The lake is unquestionably higher than the Maoris ever knew it before. It would seem to be somewhat doubtful if there has been any general rise in the water: the evidence relied on appears to the writer to be insufficient, but at the same time little doubt can be felt as to the fact of a local subsidence between the Pukeroa Hill and the sanatorium. The marks carefully placed and watched by Mr. Malfroy, the Government engineer, evidently show that such a subsidence has taken place, but to no great extent. The old water-marks on the concrete sides of three of the baths at the sanatorium all indicate the same, and that the fall has been in an easterly direction. The greater height of the water in the lake is probably due to the fact that the rain-water since the eruption runs quickly over the mud-covered surface to the lake, whilst formerly the porous strata of pumice absorbed it, and only allowed of its gradual infiltration down to the lake-level. The coining summer months will soon, however, prove the matter one way or the other.

It will thus be seen that there is a sympathetic action between the forces which gave rise to the eruption in the immediate vicinity of the Tarawera fissure, and those which cause the activity in other parts of that and the adjacent fissures—a matter which will be referred to again at a later stage. Some of the phenomena observed at Rotorua and its neighbourhood may be explicable by the action of the earthquakes in fracturing the underlying rock-masses, and so allowing the escape of steam and heated water in greater quantities; but the increase of temperature and retarded outburst of the Whakarewarewa geysers until after the heaviest earthquakes had ceased, is not so clearly connected with the same cause.