The Pamphlet Collection of Sir Robert Stout: Volume 67
Wednesday, the 9th June, was wet, with heavy showers and squalls from the south-west, which cleared up by nightfall. The evening was fine, allowing many to see the occultation of Mars by the moon, which occurred at 10.20 that night. There had been some rain during the previous week, but no great amount, and this was the first rain of winter after a long dry summer.*
The readings of the self-registering barometer at Rotorua showed no sign of atmospheric disturbance, as will be seen by the following table, the readings being reduced to sea-level: 8th June, at noon 30.2in.; at midnight, 30.08in.: 9th, at 6 a.m., 30.03in.; at 10 a.m. 29.97in.; at noon, 29.90in.; at 6 p.m., 29.80in.; at midnight, 30.01in.: 10th, at 2 a.m., 30.01 in., (eruption); at 4 a.m., 30.20in.; at 6 a.m., 30.30in.; at noon, 30.30in.
The description of the phenomena observed at the actual eruption is taken by permission from a paper read before the Auckland Institute by Messrs. S. Percy Smith and J. A. Pond, on the 12th July, with some additions and alterations derived from subsequent inquiries by the writer.
* The rainfall for June, as registered at Rotorua, was 4.74in. (Vide New Zealand Gazette, 1886, page 1296.)
Soon after the commencement of the eruption, and before the fall of the first stones, a great wind rose, which rushed down the valley of the Wairoa towards the eruption, and which branched off by Tikitapu Lake, rushing up the funnel-shaped valley there, prostrating the beautiful forest, and utterly destroying it.
* It is strange that the reports were not heard at Lichfield, only about forty miles to the west, whilst they were heard distinctly at Waotu, about six miles further off. Mr. Howard Jackson suggests that the waves of sound were deflected by the eastern side of the Patetere Plateau, and so carried over the heads of the people of Lichfield.
The immense cloud of ashes and dust which was shot high up into the air, driven first by the south-easterly wind in a westerly course, and then by the south-west wind in a northerly and easterly direction, quenched the bright moonlight and darkened the sky for hours after daylight should have appeared. The Cimmerian darkness was such as "could be felt." Charged with its burden of ash, dust, and sand, it gradually spread from the point of eruption, one edge of it taking a north-westerly direction, the other nearly cast, until it passed out to sea, dropping as it went its load of matter all over an extent of country covering 5,700 square miles of land, the extreme western point of which was on the coast near Tairua, the extreme eastern being at Anaura, a few miles north of Gisborne—points 160 miles apart. All over this area more or less fine ash, dust, sand, or scoria can be found, decreasing in quantity as the focus is left, the extreme edges being so lightly covered that the deposit disappeared with the first rain.
The height to which this dust-laden cloud and its accompanying brilliant electric discharges reached, was enormous. It was clearly seen from Auckland by several people, one of whom, Mr. R. Arthur, of Mount Eden, carefully noted the height of the topmost edge as seen against the profile of a neighbouring hill: the angle of elevation, afterwards measured by Mr. Vickerman, of the Survey Department, gives a height above sea-level of 44,700 feet, or a little over eight miles. Great as this height may appear, it is less than the observed height of the column of steam arising from Krakatoa, as measured by Professor Verbeck in 1883, which was 50,000ft. Archdeacon Williams, at Gisborne, who took some rough observations of the cloud, calculated the height to be six miles.
Mr. Eric C. Gold-Smith, District Surveyor, Tauranga, has collected page 30 the following data from gentlemen living on the coast of the Bay of Plenty as to the times that the first fall of dust and other phenomena occurred. At Tauranga it began to fall about 6 a.m., first lightly, afterwards heavier, and then lightly again, till it ceased finally at noon on the 10th. Depth of deposit, about half an inch. The darkness was so great that no gleam of daylight appeared till 10.30 a.m.; the greatest darkness being from 9.30 to 10.30, from which time it gradually became lighter till 11 a.m., when the sun was first visible. The passage of the cloud was accompanied by a strong sulphurous smell.
At Te Puke, on the evening before the eruption, there was a light east wind, changing to the south about 4 a.m. on the 10th; and at 6 a.m., just at dawn, the first fall of light dry ash was noticed, which, as the south wind freshened to heavy squalls, with rain, turned to mud, with an increase of quantity. By 8 a.m. the dust was falling steadily, but dry, the rain-squalls having ceased. At 12.30 it finally ended. Depth of deposit, 3in. At 6.30 the darkness was intense, with thunder rolling overhead, accompanied by lightning seen at intervals through the dense cloud. It gradually cleared off, till at 1 p.m. the sun was just visible.
At Maketu, the dust began to fall at 4.30 a.m., and the air was full of it at 1.30 p.m. Depth of deposit, 1in. A slight appearance of daylight at 6.50 a.m., but total darkness from 6.55 till 9.45 a.m., and more or less dark till 1.30 p.m. when the sun was first seen. Strong electrical disturbance noticed on the 16th April and 3rd, 5th, 10th, and 14th June. On the 5th June very strong, and lasting from 9 a.m. until 12.10 p.m. The telegraphist, Mr. Benner, who kindly supplies the above, says, "I had never seen anything so continuous as the electrical disturbance on the 5th until the 10th June, when the wires became altogether unworkable from 5.50 a.m. until 9.50, and continued later but not so strongly."
At Whakatane the dust began to fall at 3.30, and at 8 a.m. it was wet like wet sand; the fall ceased about 9.30. Depth of deposit, 3in. The darkness came on (eclipsing the moonlight) at 4 a.m., and it was not light till 10.30. The dark cloud appeared to travel down the Whakatane Valley, its nearer edge flashing with lightning, accompanied by rolls of heavy thunder and a rumbling noise.
At Opotiki, it was pitch-dark till 10.20 a.m., from which time it gradually brightened till noon, when the sun became visible. The dust began to fall at 3.30 a.m., and continued steadily to do so till 10 a.m., and in a lesser degree from that time till noon, when it ceased. Depth of deposit, 1½in. The cloud as it approached was seen page 31 to be illuminated with chain and forked lightning, and many balls of fire seemed to fly upwards from base to top.
At Orete Point daylight broke as usual, but it became quite dark again at 8 a.m., and remained so till 11 a.m. Depth of deposit, l in.
At Waiapu, near the East Cape, Mr. White states that it was quite dark till 11 a.m., and that the dust fell to a depth of l½in., most of which has since been washed away by the rains. It was so dark at 10 a.m. that a candle could not be seen at 10ft. distance through the falling dust.
At Motiti Island, Mr. Douglas states that it was daylight as usual, but that shortly after 7 the black cloud came over and caused it to be pitch-dark till 11 a.m., the lightning flashing and the thunder rolling through it the whole time. Depth of deposit, 1/8in.
At Oropi, (just on the edge of the deposit,) the dust first fell at 8 a.m., softly at first, quickly at 9 a.m. and slightly moist, ceased at 10 a.m. Depth of deposit, 3in. At 9 darkness set in; 9.15, total darkness; 10 a.m., bright again. In addition to the ordinary thunder there seemed to be constant explosions within the cloud, with continuous zigzag lightning, and for three hours intense cold.
At Mayor and Alderman Islands the dust fell to a depth of¼in.
At Rotorua the dust began to fall at 4 a.m. It was quite dark at 7.30, and again at 9 a.m. Depth of deposit in the township,¼in.
The earthquakes accompanying the eruption are described as severe; and, no doubt, to those who experienced them they appeared so, but, judging from the effects at Rotorua and other places, they cannot he properly so called—no light articles such as bottles or vases on shelves appear to have been thrown down, nor can these earthquakes be compared in point of severity with those experienced in the neighbourhood of Cook Strait in 1813; 16th, 17th, 19th October, 1848; or that of the 23rd January, 1855, which elevated the coast near Wellington and formed the great fissures at Wairau, in the Southern Island. They were evidently much more severe in the immediate neighbourhood of the eruption, and especially in the southerly continuation of the great fissure towards the Paeroa Mountain; for here we find the ground cracked and fissured to a considerable extent, but in all eases these cracks follow the lines of former ones, or lines of subsidence (faults, in fact), as will be shown later on. Still, notwithstanding their lightness, they were felt over a considerable area of country, extending in several cases outside the zone of volcanic rocks, and were continued in many parts for six weeks after the eruption.
The following notes respecting them have been collected:—
Tauranga.—The first shock felt at 2 a.m. on the 10th, the page 32 heaviest at 4.30 a.m., and constant light shocks and tremors were felt up to the 25th July.
Opotiki.—First shock at 2 a.m., subsequently frequent slight shocks.
Te Puke.—First shock felt at 1.30 a.m; two severe shocks, one at 4.30, the other at 9 a.m., with continuous slight shocks and tremors for two days.
Oropi.—First shock at 2.30 a.m., continued motion every ten minutes up to 6 a.m. It is worthy of note that this part of the district seems to have been more subject to continued heavy shocks up to the end of July than any other part, excepting only the immediate vicinity of the eruption.
Whakatane.—First shock noticed at 3 a.m., with continuous sub-sequent shocks, the most severe being those at 3 a.m. and at 5 a.m.
Maketu.—First shock felt at 2.30 a.m., the most severe at 4.32 a.m., and the period during which the heaviest and most frequent shocks were felt was from 4.32 a.m. to 6.30 a.m., and a rather heavy one at 8 a.m.
Matata.—Shortly after midnight; continued and severe shocks subsequently continued up to the 19th June.
Rotorua.—Slight rumbling and shake at 1 a.m., heavy shock at 2.10 a.m. and at 4.30 a.m., and since that date continued up to the end of July, when they ceased.
The earthquakes were also felt at Te Aroha, Waiorongomai, Cambridge, Lichfield, Waiapu, Taupo, and, no doubt, at numerous other places; but those named seem roughly to mark the western limit of them. At Galatea they were continuous and heavy for some days, but eastwards of that we have no record except at Waiapu*, the country being inhabited solely by Maoris.
In the immediate vicinity of the eruption, at the survey camp, Pareheru, they were felt daily from the 25th July up to the 8th August, when they ceased, the cessation being accompanied by a decrease in the activity of the various points of eruption.
* The heaviest shock of earthquake over felt by the European inhabitants of the district occurred in the first week in September (the 3rd), when also a heavy shock was felt in the neighbourhood of Cook Strait.
Subsequent observations prove that nothing was ejected from Wahanga, Ruawahia, and Tarawera but black and red scoria; and, as none of this fell after 6 a.m. on the 10th, it follows that the eruption was practically all over in six hours, as far as those mountains are concerned. But with respect to Rotomahana it is not so clear. Evidently the mud which covers the country from Rotorua to that place came from there, and this ceased in places where observations could be made by 6 a.m.; but whether the sand and ashes around Rotomahana and the southern group of craters were all ejected within that short space is doubtful. Most probably the eruption was in that locality of longer continuance. It had, however, quite ceased on any scale by the morning of the 13th, though paroxysmal outbursts from a large number of vents continued for some time longer—indeed, up to the 6th August, when the Black crater was in eruption for a short time.
When we come to consider the changes that have taken place in the face of the country, and the depth and amount of solid matter removed by the action of water flashing into steam, it is marvellous that so much energy could have been compressed into so short a space of time. Obviously the magnitude of the eruption must not be gauged by the time it lasted. It has already been stated that more or less dust, sand, or lapilli is to be found over an area of 5,700 square miles; but the country affected, in so far as vegetation has been injured and farming or grazing operations interfered with, is of much less extent, amounting to about 1,500 square miles. Even in page 34 this area, fortunately, the country brought under settlement is not very great. The farms along the coast-line of the Bay of Plenty, extending from Tauranga to Opotiki, have suffered considerably, and great loss has been entailed by the destruction of the grasses, necessitating in many instances the removal of the cattle to other districts. But, generally speaking, the country is by no means permanently affected. Already the grasses are forcing their way through the covering of dust, whilst a general opinion seems to prevail that it will eventually benefit the light soils of the district by becoming incorporated with it.
There are some very noticeable facts in connection with the distribution of the various kinds of ejecta, which can only be explained by the supposition that some of them reaheed higher strata of the air than others, and there met with currents differing in direction from the lower ones. The first outbreak, as has been said, consisted of molten scoria and lapilli derived from Wahanga, Ruawahia, and Tarawera. This seems to have been distributed with a fairly constant radius from a direction south-east from those mountains, round by the south-west and north; whilst from a direction east of north the lapilli seems to have been ejected with greater force, and so has reached a greater distance. From Galatea, nearly on the southern edge of the deposit, northwards to Te Teko and beyond it, down the Whakatane Valley, scarcely anything but fine black scoria is found, and as the mountains are approached the depth of the deposit and size of the fragments increase until on top of the mountains molten masses weighing several tons can be found. To the south, and far beyond the limit of the subsequent covering of sand and dust, the fine lapilli is found thinly scattered, whilst to the west the sand and mud have distanced the lapilli.
The mud (or, rather, wet sand), which lies westward from Rotomahana, and extends to Rotorua and thence northwards towards the coast, is not found far east of the Tarawera River. The source of this mud was undoubtedly Rotomahana; for, though Dr. Hector is probably correct in attributing, it partly to the condensation of the steam-cloud charged with dust as it met the cold south-west wind, we have only to reflect on the vast amount of water and mud which occupied the former basin of Rotomahana, and the great area of loosely-formed rocks which have there been blown out, to see that this supply is about equal to the covering laid over the country where it is found. This mud commences within a mile of the former lake, and, as there is abundant evidence that subsequent to its ejection the crater threw out dry sand and dust, doubtless in the immediate vicinity page 35 of the crater the mud has been covered over and obliterated. South and south-west of Rotomahana no mud is found, the deposit there consisting of dust and sand, and as the southern edge is approached this becomes an impalpable white powder, feeling and looking more like flour of a somewhat dirty colour than anything else. It has been ejected, without doubt, from the southern group of craters. Scattered all through the sands and dust, however, and at various levels, the fine lapilli can be seen, showing that the outburst of Tarawera and its neighbours continued on a diminished scale nearly, if not quite, as long as the other craters; but in mentioning this an exception must probably be made with respect to the flour-like dust on the southern edge—an exception which will be referred to later on. Reference to the other ejcctamenta will find a more fitting place when describing the several craters and points of eruption in detail.