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The Pamphlet Collection of Sir Robert Stout: Volume 67

Description of the Taupo Volcanic Zone

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Description of the Taupo Volcanic Zone.

As it is possible that the following account of the eruption of Mount Tarawera, which took place on the 10th June, 1886, will be read by people who have no personal acquaintance with that part of New Zealand in which the outburst occurred, or have not at hand such books of reference as exist to apply to, it is deemed advisable to preface such account with a brief description of the volcanic district known as the "Taupo Zone" of New Zealand. Some advantages may be obtained by following this course, for, though traversed by Dieffenbach in 1840, by Von Hochstetter in 1859, and later by the officers of the Geological Survey Department during the last twenty years, no description exists of many parts of the district such as is necessary to a clear understanding of the relation it bears to the recent eruption. The splendid generalizations of Von Hochstetter leave, however, little to be added but the alteration of some details, and the addition of information as to points which his limited time precluded his visiting. It was the fortune of the writer to have been engaged on the trigonometrical and topographical survey of the Taupo Zone, during the course of which, and in innumerable journeys made through and across it subsequently, an opportunity was afforded of ascending nearly every hill of any note, and of forming an intimate acquaintance with all the thermal and volcanic phenomena displayed in the district. At the same time, the account professes to be mainly a topographical one, showing the changes which have taken place, the alteration in the face of the country, and the present state of the various points of activity, based on observations made during the months of June, July, and August, 1886. Furthermore, as, during the course of the late topographical survey of the district affected by the eruption, a large amount of information was obtained bearing on the actual occurrences at the outburst and prior to it, it has been thought advisable to incorporate in this account a short description of the phenomena observed, and thus make it as complete as possible.

A reference to Map No. 1 accompanying this report will show how large a part of the central regions of the North Island of New Zealand is occupied by the volcanic rocks of the Taupo Zone. Included in that term are rocks of various compositions, but all belonging to the acidic class, consisting of trachytes, rhyolites, obsidian, pumice, and the various tufas, breccias, and agglomerates derived from them, all of which belong to the younger volcanic series of Von Hoch- page 7 stetter. They are of Tertiary age, dating from the Eocene* period, when volcanic activity seems first to have commenced in this district. And this activity has continued with varying intensity down to the present time. In the area shown on the map (4,725 square miles) none hut volcanic rocks or their derivatives are to he found, and if the rocks of the same character which have been derived from this source are added, we shall find more or less volcanic matter scattered over a country nearly as large again. Within the district will be found types of volcanic action of all kinds; active and extinct craters, immense lava flows, enormous deposits of pumice, vast areas covered with volcanic mud and sands, solfataras, fumaroles, mud-volcanoes, hot springs, lakes and rivers, healing waters of various descriptions, geysers, natural hot baths and sinter-terraces, combining to make this one of the most attractive portions of the earth, either for its natural wonders or for the picturesque beauty there displayed.

To enumerate all the points of interest within this area would be beyond the scope of this paper; but some reference to a few of the most prominent is necessary to an understanding of their general character and relation to the recent occurrences.

It will be observed that the longer axis of this volcanic zone has a direction nearly north-east and south-west, and if we continue it in the former direction we shall find that the islands off the coast belong to the same volcanic series. White Island is an active volcano, though now in the solfatara stage, its crater, half a mile in diameter, being filled by a lake but a few feet above sea-level, the water of which is warm, while along its edges arise high into the air columns of steam, which may be seen for a hundred miles round, and which deposits sulphur and other minerals in the fissures of the rocks through which it passes.

Whale Island has hot springs on it, and on the adjacent Rurima rocks steam can occasionally be seen issuing from the ground.

To the north-west, Mayor Island has one of the largest extinct craters in the district, the steep inside walls of which glisten with black shining obsidian in immense quantities; but even here the volcanic forces are not yet extinct, for hot springs are found on the eastern side of the island, near high-water mark.§

* Hector, "Outline of the Geology of New Zealand," Indian and Colonial Exhibition Catalogue, 1886.

At the present time the bed of the lake is dry.

Major Mair (Trans. N.Z. Inst., Vol. V., p. 15) says, also, "These islets at one time abounded in hot springs. In places the shores consist entirely of siliceous deposits, contorted in the most fantastic manner. Most of the rocks are, I think, trachytic."

§ Mr. Eric C. Gold-Smith, in his account of Mayor Island (Trans. N.Z. Inst., Vol. XVII., p. 421), says, "The crater is five miles in circumference, and is very well defined, being marked out by lofty hills and ridges, which vary in height from 1,162ft. down to 100ft. The interior sides of this vast amphitheatre are very precipitous, and composed of a great variety of volcanic dêbris. Obsidian and pumice are, however, the principal minerals found; the obsidian in some places having evidently cooled in layers, which gives it a stratified appearance. At others it is found in rocks, boulders, lodes, and reefs, which, glistening in the sun's rays, produce a very pretty effect. On some parts of the sides is found a conglomeration of minerals, all of which have been in a state of fusion." "In the north-west corner or curve of the crater there is a most peculiar hill, called 'Tarawakoura,' with a strong pa on its summit. It is connected with the crateredge by a narrow ridge, and, from its appearance, has been a volcano. Its sides are not very steep, but are covered with large blocks of scoria, over which has grown a dense vegetation of stunted shrubs, &c." "The hot springs are very small, being only little pools of warm—not hot—water, a few inches deep, scattered over about twenty-five yards of rough boulder-beach in Orongotea Bay."

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A line drawn from White Island south-westerly through Ngauruhoe will indicate very nearly the line of greatest activity of thermal action of this district, the principal springs, &c., being situated either on, or but a short distance from this line, and it will terminate on the summit of Ruapehu, 8,878ft. high, the highest mountain of the North Island, and which has lately proved to be in a state of activity, though hitherto always considered to be extinct. And if we pursue our inquiries back to a period preceding the present one of thermal activity, we shall find that extinct but generally perfect craters are to be found on several cones along this same line; whilst in the other parts of the district, though signs of former activity are everywhere present, no such craters are to be seen. Immediately to the north of the active mountain, Ngauruhoe, 7,481ft. high, are situated the remains of the magnificent cone of Tongariro—a name which is usually applied to its active neighbour—6,500ft. high, on the summit of which are found six craters of different ages, two of which, however, may still be said to have some life left in them, for they emit a little steam from their fissured sides; whilst on the north-west, a few hundred feet below the crater-rim, are some very active hot and sulphurous springs, called "Ketetahi" and "Te Mari," showing by their presence that the volcanic fires are still smouldering beneath the mountain.

Standing but a short distance off on either side of this central line, and just a little to the south of Lake Taupo, are Kakaramea, 4,258ft., and Pihanga, about the same height, near the summits of both of which traces of craters can be seen, whilst at the foot of the former a group of hot springs, lately visited by District-Surveyor Cussen, the first European to see them, denotes the presence of volcanic heat at no great depth.

Passing to the north of Lake Taupo, we find Mount Tauhara, 3,603ft. high, a fine conical hill, with crater on top, now extinct, and clothed at the bottom and western side with a forest of fine trees. page 9 The crater-rim is very perfect on the north, cast, and south sides, but the western—that directed towards the prevalent wind—has broken away. At its base, on the shores of Taupo, and along the Waikato River on both sides for some miles down, are found innumerable hot springs and geysers, all in a state of great activity, indicating the close proximity to the surface of the heated matter below.

From Tauhara northwards, the next cone with an extinct crater is situated at a distance of fifty-one miles from it. Mount Edgcumbe, or Putauaki, 2,945ft. high, has on its top two craters, one of which contains a small lake, and the sides of both of which are clad with forests of very old growth. The mountain itself is a most regular cone, rising out of the plain with steep curved slopes, and without the presence of any neighbouring hills to detract from its symmetrical shape. At its base is a group of hot springs, again showing that the forces which elevated it have simply transferred their locus to a point where they more easily find a vent, and proving that they have not died out altogether.

Finally, at a distance of sixty-three miles in a north-north-west direction, is situated the extinct crater of Mayor Island, or Tuhua, already alluded to, the highest point of which is 1,274ft. above sea-level.

There are thus six extinct volcanoes in the Taupo Zone, all of which have more or less perfect craters; and although they are extinct, inasmuch as no activity (excepting on Tongariro) is found in the craters themselves, every one of them has hot springs quite close to its base, showing that the volcanic forces have simply changed their position and the character of their activity, and are not finally extinct. It is well known that this is a common phase in the life-history of many volcanoes, and is due to the decreased power of the elastic gases to force solid matter up to the higher elevations of the crater-bottoms, whilst they still have power to find a vent for the more gaseous compounds at lower levels, by the aid of the fissures so common in all volcanoes. As far as the writer's knowledge goes, all of these extinct volcanoes are characterized by rocks of the trachytic or rhyolitic formation, and no scoria is anywhere present. The lavas of Tongariro are the most recent, and are plainly visible descending the mountain-sides, sometimes ending on its steep slopes in the abrupt manner common to viscid lavas of the acidic class. In one of its craters is a beautiful example of a lava-stream which has flowed across the level bottom, and has spread out in form like a club-moss. In the other cases the lava is page 10 generally hidden by surface decomposition, or overlaid by an earthy covering, due probably to sands and dust ejected from the vents, and now consolidated into an arenaceous rusty-coloured clay, the presence of which over extended areas of the Taupo Zone is a marked feature, and on the origin of which the late eruption has thrown much light, as will be noticed later on.

The volcanic energy to which is due the craters, active and extinct, and the thermal action briefly alluded to above, is apparently but the dying effort of an energy which in times antecedent to their formation far eclipsed them in magnitude and extent. The products of volcanic action which cannot be traced to any visible vent far exceed in bulk and extent of country covered those already described. Right and left on both sides of the north-east and south-west line of activity extend vast flows of trachytic and rhyolitic lavas, deep beds of pumice and volcanic mud, of enormous extent. Possibly the vents from which these lavas flowed have disappeared by denudation; or they may now be hidden by their own products. There are several reasons for supposing that some of the lakes have been craters. Taupo, for instance, notwithstanding its size, shows some indications of this. Possibly it consisted of a series of craters, the separate walls of which, by gradual erosion, have all disappeared. Observations made by Mr. L. Cussen, of the Survey Department, during his late hydro-graphical survey, tend towards this view.* The margin of the lake for seven-eighths of its circumference is formed by steep cliffs and hills of rhyolitic lava, with a generally horizontal stratification; and these cliffs at Karangahape, on the west side, rise nearly perpendicularly to a height of 1,100ft. above the lake, whilst the sounding-line dropped over the bow of the boat when its stern touched the cliff found bottom at a depth of 390ft. These cliffs are formed of alternate beds of lava and agglomerate. Motutaiko, the island near the eastern shore, formed of rhyolitic lava, rises very steeply from a depth of 400ft., and is possibly an old volcanic neck, the surrounding materials and the upper portion of which have been dispersed. Part of the eastern and northern shore of the lake is formed by cliffs of pure pumice, rising in one place to a height of 300ft. above the lake, and spreading thence north and easterly for many miles, covering the Kaingaroa Plains with a deep deposit on which nothing but a sparse vegetation of tussock-grass, tea-tree, and manoao scrub grows, and through which the copious rains filter till they reach the underlying lava and tufa, along the surface of which the water follows, appearing

* Vide Appendix for Mr. Cussen's official report and map.

page 11 at the edges of the plateau as waterfalls descending the face of the lava flöes.

There are also indications that some of the smaller lakes to the north may have in former times been craters or points of explosion. Such a centre is at or near Lake Tikitapu, around which for miles the rhyolitic lavas seem to have spread out in gently-inclined beds, all of which (at any rate, on the west, south, and south-east side) have a quaquaversal dip from that locality. Some evidence from the earthquake-cracks and subsidence-lines in the neighbourhood points in the same direction, as will be shown further on. The roughly circular form of the lake and the high perpendicular cliffs encompassing its southern side are suggestive also of a crater. Rotokawau, also—a small circular lake, with encircling cliffs and a hot spring on its margin—is possibly a crater of the same character as those in the Eiffel, formed by a gaseous explosion, as described by Lyell, Scrope, and others. Hochstetter, however, states that all the lakes of the Taupo Zone are due to subsidence.

Popular belief ascribes to the craters of Ngauruhoe and Ruapehu the vast mass of pumice which covers the Taupo Zone from end to end in varying depths; but it is more reasonable to suppose it to have emanated from some source nearer to where the greatest bulk of it is found. It is doubtless of different ages, and that which covers so vast an extent of country outside the Taupo Zone proper, generally as a thin sprinkling on the hills, with deeper deposits along the valleys and river-courses, may be the last effort of some of the extinct craters described, as well as of the active ones, Ruapehu and Ngauruhoe. The great depth of pumice however, around the north end of Taupo and on the Kaingaroa Plain, is more likely to have been formed at the time when the great rhyolite lava streams around that lake and the tufas to the north were exuded from vents now lost.

The north shore of the lake is formed by deep pumice-beds, but at no great depth the lava flow will be found, as witnessed at the Huka Falls, three miles below the outlet, and along the lake-coast south-westward. This lava would appear to have flowed in a northerly direction under what is now the Kaingaroa Plain, and in its extension northwards it becomes tufaceous, as might be expected, until it finally terminates in the wall-like northern end of Kaingaroa, a few miles south-cast of Tarawera mountain. It is everywhere overlain by pumice more or less deep, but decreasing in amount from south to north. The manner in which this pumice-deposit wraps round the isolated slate hills in the neighbourhood of Runanga and northern end of the Kaimanawa Mountains, forming a generally level plain, page 12 tends somewhat to the belief that it was deposited in a lake; but the evidence has not been followed out sufficiently to allow of this being stated as an ascertained fact. Large logs of carbonized wood are sometimes found in this locality, buried deep in the pumice-strata, which may have been carried there by water, unless indeed, they owe their present position to a similar cause to that which placed the logs around Rotomahana, to be referred to later on.

If a line is drawn from the summit of Ruapehu, cast to within fifteen miles of the coast, and thence north-easterly towards the East Cape till it strikes the road from Gisborne to Opotiki, and thence to the coast on the Bay of Plenty by that road, whilst another is made to extend from Ruapehu northerly to near Matamata, and thence to the coast at Tauranga, we shall include an area of country of about 10,775 square miles, over the whole of which more or less pumice is found on the tops of the highest hills, with deeper deposits in the valleys. Nor is this pumice always in a fine state of division: on the hills inland of Hawke's Bay and far to the north the lumps are frequently of the size of an orange, and at the eastern bases of the mountains it has often accumulated in drifts, as if by the action of the wind blowing it over the ranges* The Waikato River, which drains the larger part of the Taupo Zone, is noted for its perfect terraces, all formed of pumice; and many other rivers, such as the upper branches of the Wanganui, are similarly terraced to a depth of hundreds of feet—pure pumice being the formation—the bulk of which has doubtless accumulated in the lower grounds by being washed off the hills. On many of the mountains within the Taupo Zone the pumice is but a few inches deep, whilst immediately at their bases the valleys are filled to a depth of 200ft. with it, and these now form level plains, once the beds of lakes, through which the water has worn deep channels down to the bed-rock, exposing the section of pumice, often containing large fragments of carbonized wood. A good example of these former lake-basins filled with pumice, three in number, is to be seen under Tuahu, the steep ascent on the coach-road from Rotorua to Taupo. Many of the minor plains within this? district, which have level surfaces surrounded by hills with one or more low outlets from them, and the surface of which is formed of deep pumice, must have been lakes. The worn, shore-like cliffs, the stratified pumice, all point to their having been such; and the origin is in many cases due to the valleys in which they lie having been blocked, and the waters dammed back, by pumice and volcanic dust.

* For further particulars of the pumice-deposit, see Trans. N.Z. Inst., Vol. IX., page 565.

page 13 The size of the blocks of pumice varies much in different places, showing doubtless, that it originated from many points. On the shore of Taupo, 50ft. above the lake, can be found blocks containing as much as a thousand cubic feet. On a level plain (an old lake-bed probably) not many miles north-west of Runanga the ground is so covered for ten or fifteen square miles with large blocks of pumice, closely packed together, that no horse can cross it, whilst the adjacent undulating Kaingaroa Plain has few blocks of any size. The immediate vicinity of Ruapehu and Tongariro has less pumice on the surface than probably any part of the Taupo Zone: it is present in fine particles, but to no great extent, the surface being formed by a dark-brown earth or loam, forming a more fertile soil than is usual in the district.

In addition to the craters, active and extinct, the lava and pumice-beds, the district is studded with isolated hills of a characteristic shape and appearance. They take the form of a flattened plateau, or somewhat conical hill, but always encircled by steep precipitous mural cliffs of trachytic or rhyolitic lava, the decomposed portions of which form a more or less steep talus below. Good examples will be found in Ngongotaha, Haparangi, Tutuhinau, Tutukau, Ngautuku, Moroa, Tuahu, Nganiho, Tumunui, Marotiri, &c. These and other hills have all a strong family likeness and a somewhat similar height, varying from about 2,500ft. to 2,800ft. Their origin is somewhat obscure. Hochstetter, who saw some of them, believes them to be the remains of a former plateau which extended from Horohoro eastwards and southwards. The hills in question are all composed of the two lavas above mentioned, whilst the Horohoro Mountain, and the plateau extending northward from it, are composed of tufas, forming possibly the extension of the lava-plateau westward, where we should naturally expect to find this class of rock—that is, outside of the lava. It is noticeable that all the hills of this class are situated to the north-west of the great fissure to be referred to later on, and that nearly all of them are within the boundaries of the area enclosed by that and the most westward fissure.

Some indications observed from the peculiarity of their shapes in more than one instance tend to the probability that they are the denuded remains of vents or volcanic necks, formed by the harder and more consolidated portions of the lava-streams where they issued from the depths below; their extensions having disappeared by ordinary meteoric agency.

The forest-clad region lying on the west side of the Taupo Zone page 14 north of the Waikato River, known under the general name of the Patetere Plateau, and which ends to the south in the Horohoro Mountain—whose perpendicular inaccessible cliffs are prominent landmarks over a large extent of country—is composed of trachytic tufaceous rocks, generally soft, and grey in colour, overlain by thin and local strata of pumice and the rusty arenaceous loam before referred to. Its average height is about 1,800ft. to 2,200ft., and on its western side it slopes for a long distance by easy grades towards the upper waters of the Thames River, whose numerous brandies have cut deep gorges into its lower parts, and frequently formed canons with steep sides of tufaceous rock.

The superficial rusty-coloured clay (or earth, for it has no plasticity), together with the lighter deposits of pumice, cover a very large area in the Taupo Zone; but they are generally confined to the western side of the main north-east and south-west axis. Within that area they form the subsoil, and vary somewhat in composition, being occasionally fertile, hut generally only partially so. Abundant evidence is to be found that they are due to one of the latest efforts of volcanic agency in the district. The clay covers the country as with a mantle of snow, taking the same inclination as the slopes of the present hills; and frequently underneath it can be traced a former land-surface. It is, in fact, an exactly similar deposit to that ejected by the craters recently formed, with this difference: that it covers an enormously greater extent of country and is of a different colour, due, doubtless, to the action of rain-water on the iron matter contained in all volcanic ejecta. The recent deposit from Rotomahana is grey in colour; hut time will doubtless alter its appearance to that of the older deposits. Its great extension has hitherto prevented a proper understanding of the nature of this deposit; but if a minor explosion such as that of Rotomahana can cause such changes in the face of the country in six hours, what would not a few similar explosions on a somewhat larger scale effect over this large district? Evidently this rusty-coloured clay fell in an exactly similar manner to the mud at the Wairoa—in the form of an exceedingly heavy rain, charged with mud. It was accompanied by simultaneous deposits of pumice; for we find this substance gathered in hollows or pockets in the loam, and these also conform to the slopes of the ground. Generally the hills are sprinkled with it to a few inches deep, showing that the ejection of pumice was the latest effort of the vents from which both deposits came.

From what has been said above it will readily be inferred that the covering of clay and pumice is, geologically speaking, of quite page 15 recent origin. It was subsequent to the changes which have taken place in the contour and depth of some of the lakes, as is proved by fading it spread in the same equal manner over the former bed of Rotorua. Both this lake and that of Taupo have well-defined terraces, or ancient shore-lines, encircling their present basins, the former at about 120ft., and the latter at about 100ft., above their present levels.

If we turn now to a consideration of the existing points of greatest thermal activity, as exhibited in the geysers, solfataras, and fumaroles, we shall find that the same axial line from Ruapehu to White Island marks also the direction along which the greatest activity is displayed. The accompanying map (No. 1) indicates the several groups of hot springs, &c.; but it is impossible on so small a scale to show the individual springs, which may be numbered by hundreds, and of varieties innumerable. It will suffice to point out that the greatest activity in the district is seen at Tokaanu, at the south end of Taupo; at Wairakei, near the north end; at Orakeikorako, on the Waikato, but at a short distance off the line to the west; in the Waiotapu Valley; at Rotomahana, the most active point of all, and which is nearly half-way between Ruapehu and White Island; and lastly, at Ohinemutu, Whakarewarewa, and Tikitere, points much further to the west, and which are probably on another fissure, which nevertheless, has an intimate connection with the one under consideration, as will be seen later on. By varying this line very little from a strictly lineal direction, and making it a slightly sinuous one, we shall find that in addition to its denoting the region of greatest activity of thermal action, it will follow well-marked features in the physiography of the country, characterized by river-valleys, low plains, lake-margins, and the comparatively low fiat water-parting between streams draining into Rotomahana and the Waiotapu. Along this somewhat sinuous line running water in considerable volume is Hound everywhere but on the above-named water-parting, and there it is absent for not more than half a mile. These facts, taken in conjunction with the presence of all the craters, both active and extinct, in the immediate proximity of this line, point directly to the great Probability—nay, certainty—that we have here a line of weakness in the earth's crust, in which the molten matter from below is quite near the surface. A fissure doubtless exists along which the lava wells up, seeking a vent to escape the pressure of the incumbent strata, and down to which part of the water of the rivers finds its way by percolating through crevasses and fissures, its contact with the heated matter giving rise to the thermal phenomena exhibited. It would be page 16 contrary to observed facts in other countries to suppose that this fissure takes a mathematically straight line from White Island to Ruapehu: the weight of superincumbent rocks, of different degrees of hardness or method of formation, would render it somewhat devious from a true line, though its general direction throughout varies but little from such a one. We shall see later on, that the recent eruption, although it deviates somewhat, but to no great extent, from the general direction, is on the line of this fissure. That such a fissure is deep-seated, and intimately connected with the larger and more general lines on which the two Islands are built up, is proved by its parallelism to the great mountain-backbones of both Islands. The opinion may also be hazarded that it is as ancient as the volcanic region itself, and possibly is the same from which emanated the first signs of activity in Eocene times, when it was probably submarine.

Whilst recognizing this as a great fissure of the earth, and the principal one of the district, it is quite probable that others and nearly parallel ones exist. An almost exactly parallel line drawn from the hot springs at Orakeikorako to the hot springs at the end of the eastern arm of Lake Rotoehu, indicates another line along which are a number of hot springs and fumaroles of considerable activity, and which line passes along the wall-like face of the Paeroa Range, and through the old lake-basin of Waikorua, a place which is riven by earthquake-cracks, and in which are several deep crater-like holes, probably the sites of former thermal action. The southern half of this line seems to mark a fault with a downthrow to the north-west, with the Paeroa Range, 3,214ft. high, rising on the east, and with the low undulating country of Ratoreka to the west.

Although the presence of a fissure in this locality seems to he borne out by the facts as stated, another hypothesis is possible with respect to part of it. By starting from the same place, Orakeikorako, and taking a direction somewhat more inclined to the cast, slightly curving it at the north end of the Paeroa Range, it will be found to take the direction of the recently-formed fissure, and thus form a connecting-link between the two, by lines converging and meeting in Tarawera Mountain, or in Rotomahana crater.

Again, at about twelve miles to the north-west of the great fissure, and lying nearly parallel with it, a line drawn from the hot springs on the Waipapa Stream to those on the Kaituna River near Taheke, Rotoiti, seems to indicate—by the presence of several hot springs, geysers, fumaroles, and mud-volcanoes—another fissure of about thirty-five miles in length. Along this line are some very celebrated springs, such as Whakarewarewa, Ohinemutu, &c., with page 17 the hot-mud caldrons and boiling sulphurous waters of Tikiterc a short distance off it to the cast, and the Waimahana Springs on the Waikato River to the west, these latter being the most westerly or north-westerly ones of the Taupo Zone. And here again, as in the great fissure, we find this one following, (or being followed by,) a marked depression of the country, along which the main streams flow, and on which are situated the lakes Rotorua and Rotoiti. Somewhat to the north-west of the continuation of this line we find another hot spring near Maketu, close to the coast of the Bay of Plenty, and, equally with the middle fissure, its southern part seems also to indicate a fault running along the edge of the Horohoro Mountain and the Patetere Plateau; but it is here much more obscure and more sinuous than the opposite one of Paeroa.

East of the great fissure, no signs of thermal action are found until the volcanic district is left, and a point well within the old slate rocks forming the main range of the Island is reached. At Tarawera, on the Napier coach-road, a distance of about forty-four miles from Taupo, is a hot spring, and south of that again, at the foot of the Ahimanawa Mountain, are a few hot springs and a small hot stream, none of which, however, are of much importance, nor are they connected with volcanic rocks.

Whilst the number of places within the Taupo Zone at which hydro-thermal action is still in full force may be counted by the thousand, and in which every known variety of such action is; exhibited, it is the prevalent opinion of both learned and unlearned that in former times the forces producing it were far more active, and in some respects on a grander scale, than at present. No one can traverse the district without seeing on all sides evidence of former hot springs, now extinct. Even within the memory of those living, geysers have ceased to play, temperatures have sunk, and the activity generally appears to have decreased. The traditions of the Maoris bear witness to the same facts; and amongst a people so observant of natural phenomena, and whose traditions have been handed down orally from father to son with such scrupulous care as to make them almost equal in value to documentary evidence, it is not likely that such changes would escape their attention. Making due allowance for possible exaggerations in these traditions, there is no doubt that they are correct in stating that the thermal activity has been decreasing. But it is to be observed that none of their traditions speaks of any such catastrophe as that which has lately occurred; indeed, it is impossible to believe that any such occurrence has been witnessed by the Maoris during the five or six hundred years of their occupancy of this page 18 country, or the signs of it would still be visible to any one having a habit of observation*

That the Maoris were very observant, however, of natural phenomena is well known, although the reasons they assign as the original causes of such phenomena or events appear to us often absurd, but at the same time frequently poetical. The well-known story of the origin they assign to the volcanic fires of the Taupo Zone shows this observant faculty, while, at the same time, exalting the powers of one of their great ancestors, Ngatoroirangi, who was the high priest of one of the original canoes—the "Arawa"—in which the first emigrants came to this country; and this legend, as pointed out by Hochstetter, truly indicated the line of greatest activity. It is abridged below, as taken from Mr. S. Locke's translation.

To recapitulate briefly what has been stated with respect to the Taupo Zone: we find that the volcanic rocks extend immediately to the westward from, and are abutting against, the much older series of slate rocks of the backbone range, of Palæozoic age; that the rocks are acidic in character; that a definite axial line, running about north-east and south-west between the extreme points—each end marked by active volcanoes—indicates the line of greatest present activity, and that this is probably a fissure in which the molten lavas are everywhere near

* The eruption of the Waikite geyser, at Ohinemutu, which occurred eight generations ago, cannot be compared, of course, to that of Tarawera, although it caused the death of a number of persons, belonging—strange to say—to the same Tuhourangi Tribe who suffered so much lately. These people, it seems, were camped outside of the Ohinemutu village when the geyser exploded, throwing mud and stones all over that part of the ground, killing and scalding many; but the village itself is said to have escaped any damage.

"This is an account of one of our renowned ancestors who visited the sea of Taupo, and the open country, the forests, and the plains around. He came to this island from Hawaiki in the 'Arawa' canoe, which landed first at Whangaparaoa (near the East Cape), then sailed on to Whakatane and Maketu. After Ngatoroirangi had resided on the coast for a time he travelled inland by way of Kanakaua, Ruawahia, and Te Punatakahi After crossing the Kaingaroa Plains he reached Tauhara Mountain, which he ascended, and from thence looked down on the sea of Taupo and at the snow-capped Tongariro in the distance. Ngatoroirangi then descended to the shores of the lake, near Waipahihi, and performed incantations and erected a tuahu, naming it Taharepa. When he discovered there was no fish in the lake he scattered the threads of his mat on the waters and performed religious rites, and the lake at once contained fish—viz., the inanga and the kokopu. He then travelled along the shores of the lake and ascended Tongariro, and was there benumbed with the cold on that snowy mountain. His companion, Ngauruhoe, died here from cold. So Ngatoro commenced calling out to his sisters to bring him fire from Hawaiki; for they had been left behind there. His sisters heard him and came at once, bringing fire. Their canoe was a taniwha. The sisters landed at Whakaari (White Island), and here lit a fire (geyser), and then came on to the main land at Umapokapoka (a geyser), and then travelled on by the Kaingaroa Plains. The sisters lit a fire (geyser) at Tarawera Lake, then ascended a hill and looked down on Rotorua Lake; one of them slipped down here, so they called the place Te Hemo, and lit a fire (geyser) there, and then proceeded on to Paeroa and Orakei-korako, where they lit another geyser, and shortly after arrived at Taupo. But But Ngatoro had returned to Maketu, so the sisters determined to join him there," &c. (Trans. NZ. Inst., Vol. XV., page 435.

page 19 the surface; that it is along this line the recent eruption has taken place, and further, that the volcanic rocks on either side of this line differ somewhat in character; and finally, that the volcanic forces have been gradually dying out, the present activity being hydro-thermal rather than volcanic.