on the Geology of the North Island
of New Zealand.
Up to the time when the first systematic colonization of New Zealand commenced, but little appears to have been known of the Geology of the country. The prevailing idea concerning the North Island was, that it was a region of volcanic rocks only; and the greenstone weapons of the aboriginies, the material for the manufacture of which was said to be procured from some mysterious lake in the Middle Island, proved that rocks of Nephrite were found there.
In the year 1839, however, the Directors of the New Zealand Company, with intelligent foresight, selected a talented and experienced naturalist to proceed to the colony with their first expedition in the ship “Tory,” and to the person so appointed to report on the Natural History and Geology of the colony, Dr. Ernest Dieffenbach, we owe our first systematic information as to the Geology of the North Island. About the same time, the late Mr. John Bidwill, a man of excellent scientific attainments, and known to fame from the Araucaria, which he discovered at Moreton Bay, and which bears his name, performed a journey through the North Island; and, having succeeded in effecting the ascent of Tongariro, or, more probably, of its lateral cone, called Ngauruhoe, gave interesting information concerning the volcanic system of the interior, and other geological matters. I am glad to have this opportunity of bearing testimony to the merits of an old and valued friend. The communications of Mr. Walter Mantell to the Geological Society also threw much light on the Palæontology of New Zealand, and his observations on the deposits of moa bones, and subsequent deductions as to the existence, at the same period, of man and the moa, are extremely curious and interesting.
Contributions towards the knowledge of the rocks of the colony continued to be made from time to time by Mr. Charles Heaphy and Mr. Theophilus Heale, of Auckland.
In 1845, “Darwin's Voyage of a Naturalist” was published, with some account of the Geology of the Bay of Islands.
In the year 1855, Dr. C. Forbes, R.N., of H.M.S., “Pandora,” contributed a valuable paper to the Geological Society on the Geology of New Zealand.
In 1856, the Rev. R. Taylor, of Whanganui, published his work on New Zealand and its inhabitants, which contains the results of his long geological experience.
In 1859, Dr. Thomson's “Story of New Zealand” was published, in which he refers instructively to the Geology of the colony, and describes some points of great interest. In the same year, Dr. Hochstetter arrived in New Zealand, in the I. and R. Austrian frigate “Novara,” and commenced that investigation of the provinces of Auckland and Nelson which has resulted in the valuable contributions to science now before the public. In this investigation he was assisted by the present Government Geologist of Canterbury, Dr. Julius Haast.
In the province of Wellington, Mr. William Lyon has done much, during a long series of years, to advance the cause of Geology, and Mr. Thomas Dawson Triphook has investigated the rocks of the province of Hawke's Bay. From him, in the year 1860, I obtained a valuable “tabular view” of the rocks of that province.
Having now brought down these observations on our previous knowledge of the North Island rocks, I will state that for the purpose of this essay, I shall principally make use of the results of Hochstetter's investigations in the province of Auckland, and my own observations in the southern part of the island, while engaged as Government Geologist of the province of Wellington, from the year 1861 to 1864. In this investigation I received valuable assistance from the Rev. W. B. Clarke, of Sydney, whose zeal for the advancement of Geological knowledge is so well known.
As a considerable portion of the North Island of New Zealand has never been subjected to a systematic Geological investigation, many parts of its still require to be scientifically examined, and as indeed too short a period has been devoted to the study of any one part of the Island, I can do no more than collate all the evidence that is already before the world on the subject—which is, at all events, considerable, and amply sufficient to give a good general idea of the age and character of the rocks, and of the changes which have taken place in them.
In the North Island there appears to be an absence of the older Crystalline and Plutonic rocks, and the various formations appear to be principally composed of a flooring of Palæozoic age, overlaid in general by sedimentary Tertiary rocks, which cover an extensive area
(comprising about half the island) to the northward and eastward of a line struck from the southern slopes Mount of Egmont and Ruapehu, and are broken through by volcanic rocks, which, to a considerable extent, overspread their surface.
The secondary, or Mesozoic rocks, as yet discovered, or positively known, occupy an area of moderate extent, and the greater part of the surface of the island is covered by the above strata of Tertiary age, both sedimentary and volcanic.
Before entering upon a description of the Palæozoic rocks, it is however necessary to state that there is reason to suspect that a considerable proportion of the rocks now classed as Palæozoic may have hereafter to be transferred to the Mesozoic list. Dr. Hector thinks that the sandstones and slates associated with the plant beds near Wellington, have a strong resemblance to Mesozoic rocks elsewhere in New Zealand, and that they will probably be found to lie unconformably upon the older diorite rocks of the neighbourhood, while I have a decided impression that the rocks of the ranges at Cape Palliser will prove to be of later date than those of the Rimutaka range on the eastern side of the Wairarapa. With the above understanding, it will be as well, for present purposes of description, to consider all the apparently old and highly inclined rocks of the great leading ranges of mountains as of Palæozoic age.
Primary or Palæozoic Rocks.
There is reason to suppose that the Palæozoic rocks, which are almost invariably found highly inclined, decrease in Geological age from west to east. They appear to have been subjected during the lapse of ages to extreme lateral pressure, which has thrown them, particularly towards the eastern or main ranges, into abrupt mountain ridges, extending in a N.N.E. and S.S.W. direction, and enclosing only very narrow valleys. Except where these mountain ridges rise from out of the Tertiary covering, the indication of their existence can often only be proved at remote spots, where the violent torrents near the sources of the great rivers have scooped out deep gullies in the soft Tertiaries and left a flooring of old slates, or sandstones, exposed in their beds.
Although the volcanic chain of Ruapehu and Tongariro may be said to be the leading feature of the North Island, rising, as it does, from a very elevated plateau, one of its cones, Ruapehu, being the
highest mountain in the island, yet we cannot consider this isolated chain as the leading range, but must award a higher structural importance to the Palæozoic ranges further to the eastward. These ranges, though broken, pass completely through the island from the coast near Wellington in a N.N.E. direction. They have an extreme width of about twenty-three miles, and a minimum width of about four miles, and form a succession of gigantic “hog-backs,” rising from Cook's Strait, to an extreme elevation of about 5000 feet, nearly opposite the Horowhenua river and lake. At this latter place they attain the greatest width, and afterwards sink to an altitude of 1300 or 1400 feet, but at the gorge of the Manawatu their breadth is decreased to four or five miles. Here the striking feature is observed of a river (the Manawatu), rising on the eastern side of the main range, passing through a narrow gorge, and falling into the sea on the western side of the island. This phenomenon though occurs in the opposite direction, viz.:—from west to east with various Hawke's Bay rivers. The mountains which may be regarded as the southernmost group of the main range, pass under the general names of Tararua and Rimutaka, but have various spurs and off-shoots bearing subordinate denominations.
From the northern side of the Manawatu Gorge, the main range, which is composed of rocks of a similar geological character, continues its course to the N.N.E., under the name of Ruahine, attaining an elevation of 5000 or 6000 feet, and, like the above described more southern group, drops again to the northward, to be succeeded by the Kaweka range, and that again by other ranges continuing the line to Hick's Bay, westward of the East Cape. These ranges in the latter part of their course have never been surveyed, nor even examined, but their general character has been roughly determined by observation in passing along the coast.
Parallel ranges of Palæozoic rocks are found both east and west of this line, but none of them like the above described mountains, traverse the Island from end to end.
The rocks of these ranges consist of sandstones of different kinds, varying from of a soft decomposing texture and yellow colour, to a hard compact blue and grey semi-crystalline rock, plant beds, tentaculite beds, slates (some being pyritous), diorite schist, jasperoid rocks, and a little serpentine.
More modern eruptive rocks also appear to penetrate the ranges, as
seen at Muka Muka, and elsewhere, consisting of amygdaloidal trap and basalt.
The line of strike of these eruptive rocks will probably be found to be shown by the jasperoid rocks, supposing these to have been metamorphosed into their present state by the effect of the intrusive dykes.
The fossils that have been found in the Palæozoic ranges are few and indistinct, and, as far as we know, are confined to those discovered by myself in the neighbourhood of Wellington. One from Belmont Hill; above the western entrance of the Hutt Valley, is supposed to be either “Theca” or “Dentalium;” and some vermiform casts, probably “Tentaculites,” have been found at the same place.
The most frequent remains of organic life however, are to be found as markings, or seams of carbonaceous substances. Organisms are found at Porirua, and at Oriental Bay, near Wellington, where they seem to indicate a Mesozoic age; but they, in both cases, are too obscure to found a theory upon, and we must await the discovery of more distinct specimens before drawing decided conclusions.
Thin seams of an impure Graphite are found at a great variety of places—on the Pitone road near Wellington, at the Mungaroa Hill, at various points on the Rimutaka Mountains, in the mountain part of the valleys of the Waiohine, the Wai Ngawa, and the Ruamahanga, in the Waikanae, the Akatarewa, and particularly in the upper part of the Otaki valleys.
The inclination of these old rocks is very great, from 45° to vertical—(on an average perhaps 70°). They must have been folded by great lateral pressure; and at various points on the south coast, particularly between Wellington harbour and the Wairarapa valley, there are excellent examples of contorted strata.
These rocks are freely jointed, and consequently break readily into angular fragments. They are therefore, in general, unfit for building purposes.
To the eastward of the main chain a parallel range of Palæozoic rocks rises from Cape Palliser to an elevation of about 3000 feet above the sea; but at or about the latitude of the Pahaoa river its Palæozoic rocks pass beneath the Tertiaries, with the exception of a few insignificant ridges, which may be seen further to the northward. To all appearance no Palæozoic rocks are found along the same line further north than the Kaiwhata river, on the eastern side of the Wellington province, nor in those parts of the provinces of Auckland and Hawke's
Bay which lie to the eastward of the main Palæozoic range. The continuation in the Middle Island of similar rocks to those of the main range, is said by Dr. Haast, to lie between the Wairau and the Awatere.
To the westward, the first great upward undulation of the Palæozoic rocks is found in the Kaimanawa range—the “heart eater.” This range commences its rise from beneath marine Tertiaries and volcanic deposits, to the eastward, and about ten miles from the base of Ruapehu, assumes an elevation of 5000 feet opposite Lake Taupo, and passes in a N.N.E. direction towards the Bay of Plenty, under the subsequent names of Te Whaiti or Whakatane range. In the maps, Ruahine is generally made to curve to the westward, to meet the Kaimanawa range. This is incorrect, and gives a false view of the topography of the country. Kaimanawa is parallel to Ruahine, or its successors, not continuous with them; nor do they curve to the westward towards it.
Passing farther to the eastward, the Palæozoic ranges are found at Coromandel harbour, and at Cape Colville, and there form the boundaries of both sides of the Frith of the Thames. For a description of these rocks we must refer to Hochstetter, who writes as follows:—1
“The oldest rock I have met with in the province of Auckland belongs to the primary formation. It is of very variable character, sometimes being more argillaceous, of a dark blue color (when decomposed, yellowish brown, the color generally presented on the surface), and more or less distinctly stratified like clay slate—(at Maraetai on the Waitemata). At other times the siliceous element preponderates, and, from the admixture of oxide of iron, the rock, has a red jasper-like appearance (at Waiheke, Managanese Point). In other localities it is more distinctly arenaceous, resembling the old sandstones of the Silurian and Devonian systems, called Grauwacke (at Taupo, on the Hauraki Gulf). As no fossils have yet been found in this formation in New Zealand, it is impossible to state the exact age. I am, however, of opinion that these argillaceous siliceous rocks will be found to correspond to the oldest Silurian strata of Europe. In these rocks occur the copper pyrites, which has been worked for some years at the Kawau and Great Barrier, the Manganese (Psilomelane), at Waiheke, and the gold-bearing quartz at Coromandel.”
“The gold which is washed out from the beds of quartz gravel in the rivers and creeks flowing down from both sides of Coromandel range is derived from quartz veins, of crystalline character and considerable
[Footnote] * Fischer's translation p. 14.
thickness, running in a general direction from north to south, through the old Primary rocks, which form the foundation of the Coromandel range. In some places these veins stand up like a wall on the summit of the range to the height of eight or ten feet. The clay slate rock itself is exposed only at the bottom of deep gorges which form the channels of the principal streams. In almost all places it is covered by large masses of trachytic tuff and breccia, of which the hils surrounding the harbour of Coromandel are composed. The magnetic iron sand which, in washing, is found with the gold, is derived from the same source as all the magnetic iron sand of New Zealand,1 namely, from the decomposition of Trachytic rocks. Small veins of quartz of amorphous character—that is, not crystalline, but in the shape of chalcedony, carnelian, agate, and jasper—are found in numerous places on the shores of Coromandel. These veins, occurring in Trachytic rocks are quite different from the auriferous quartz veins in the primary formation.”
“The primary formation occurs, to a more considerable extent, to the eastward of Auckland, in ranges on both sides of the Wairoa River, attaining an altitude of 1500 feet above the level of the sea—and striking from thence northward, over Waiheki and Kawau to the Bay of Islands. In a southerly direction they extend, through Hakarimata and Hauturu range, parallel with the west coast, to the Mokau district, where, at Wairere, the Makau River falls in a magnificent cascade over a lofty precipice of that rock.”
“The same formation occurs again in the Rangitoto Mountain, in the upper Waipa, and west of Taupo Lake, in the Tuhua mountains.”
To the southward of the country described by Hochstetter, Palæozoic slates and sandstones are found cropping out in the bed of the Waipare, a tributary of the upper Whanganui, and from Maori report old slates will probably be found in a similar manner in the bed of the Whakapapa and other tributaries of the Whanganui, and perhaps also at some point of the upper part of the main stream itself.
At the Waipare, Tertiary sandstones and volcanic tuffs have been cut through by the action of the stream down to the Palæozoic base. The latter rock, at this point, is a slate traversed by threads of quartz.
To the eastward of the Hauraki gulf, the Palæozoic rocks retain somewhat, but in a lesser degree, the bold angular form of the main ranges to the eastward of the island, but on the western side of the gulf, as at Kawau, they frequently sink to comparatively a few feet above the
[Footnote] * Magnetite occurs in the Chloritic Schists of Otago.—Ed.
sea level, and are often covered by a thin coating of newer Tertiaries, by which their characteristic outline is destroyed.
Secondary, or Mesozoic Formations.
It is quite possible that Secondary rocks may exist to a considerable extent in the North Island; but, if so, they must be in great part either covered up and hidden by rocks of a later era, or be represented by some of the rocks now classed as Palæozoic.—To Hochstetter belongs the merit of discovering the only decided Secondary rocks which have yet been found, and the following is his description of them:—1
“A very wide interval occurs between the Primary rocks of the North Island and the next sedimentary strata that I met with. Not only the upper members of the primary series are absent, but also nearly the whole of the secondary formations. The only instance of secondary strata that I have met with consists of very regular and highly inclined beds of marl, alternating with Micaceous sandstone, extending to a thickness of more than 1000 feet, which I first saw on the South Head of the Waikato, and afterwards met with on the western shore of Kawhia Harbour.”
“These rocks possess great interest, from the fact that they contain remarkable specimens of marine fossils, which belong exclusively to the secondary period; especially Cephalopods of the genera Ammonites and Belemnites, there being several species of Belemnite, but all belonging to the family of Canaliculati. These are the first specimens of these genera which have been discovered in the regions of Australasia.”
“Secondary rocks may probably be found in some other parts of the west coast, and occur, as I have been kindly informed by the Rev. A. G. Purchas, in the Harbour of Hokianga, but everywhere of limited superficial extent.”
To this short description of the Secondary rocks, I can only add the possible secondary character of sundry limestones and sandstones on the east coast of the Wellington province, but in which no distinctive fossils have as yet been found. The southern limit of these is at the White Rock, Barton's station, and they extend, at all events, as far as the northern boundary of the province of Wellington, occupying, with some decided Tertiaries, which rest upon them, a breadth of about seven miles from the coast.
[Footnote] * Fischer's translation, p.17
Tertiary, or Kainozoic Formations.
By far the greater part of the North Island of New Zealand is covered by rocks of Tertiary age.
The oldest of the Tertiary rocks would appear to be beds of brown coal, with accompanying shales. It is necessary to observe that there are beds of lignite found in the newer Tertiary sandstones, which may be defined as lignites, not brown coal.
These brown coal and shale strata are succeeded, in the Wellington province, by strata of blue clay and limestone, with Cucullœa singularis, of which beds this fossil is most characteristic. The blue clay is again covered by a succession of strata of sandstones, and arenaceous limestones, both being fossiliferous, and attaining in some parts a great thickness. Above these again a drift gravel is often found. In the Whanganui, Rangitikei, and other west coast rivers, some of these Tertiary strata are marked in a remarkable manner, with numerous horizontal bands, or lines, of boulders, or concretions surrounding boulders or some other substances, such as fossil shells. These boulders are generally either of Igneous or Palæozoic rocks. In the southern part of the Island, these Tertiary formations, or some of them at least, are found on both sides of the main range, lying generally horizontal or slightly inclined, and abutting on the Tararua and Ruahine ranges on both sides. They then stretch northward on the west side of the range, until they reach, and become mixed with, the volcanic products of the interior, continue to the N.W. probably all through the province of Taranaki (fringing Mount Egmont), into the province of Auckland—the Tertiaries of which will be hereafter described. From the western shores of Cook's Straits these Tertiaries have a gentle slope upwards until they reach to within half-a-mile of Tararua and Ruahine, where the inclination becomes greater, and the beds appear somewhat disturbed, as if the range had been thrust through them, or pressed against them from the eastward, and in support of this view there is a line of fault along the western, or Wairarapa, side of the ranges, in which the gravels of the plain, resting against the ranges are fissured, and that side of the fissure next the ranges is raised some four feet above the other.
In a similar way the nearly horizontal Tertiaries at the Whanganui part of the basin, are tilted at an angle of perhaps 20°, on approaching the volcanic chains.
We may, therefore describe the whole of the North Island, except the Palæozoic ranges, or, at all events, all that part of the country to the
westward of the main ranges, as the great Tertiary field of New Zealand; and the country sloping from the flanks of Tararua and Ruahine, from the Patea country and the end of Kaimanawa, and from the great volcanic chain, and also the slopes of Mount Egmont, and into, perhaps across, Cook's Straits, in fact, all the slopes towards Cook's Straits, as the great Tertiary basin of the country. On the eastern side of the main range, the usual Tertiaries are found, except the brown coal series, which has not yet been discovered, except in small quantity, but Cucullœa singularis is found on a tributary of the Pahaoa, and the usual Tertiary fossils abound in many places. The eastern rocks generally dip slightly to the westward, but, at about seven miles from the east coast, they are thrown up at a very high angle, where the edges of the upturned strata form a most striking series of peaks, called Taipo, and supposed by the aborigines to be the haunts of Taniwha, or other mysterious and mythical animals; and certain sandstones and limestones, of undetermined age, succeed them, which, as before stated, are probably of Mesozoic age.
The Tertiary rocks pass northward from the eastern side of the province of Wellington, through that of Hawke's Bay and appear to extend throughout along the east coast, to the East Cape, at which point they lie horizontal, and extend from that Cape to the nearest Palæozoic rocks in Hick's Bay, a distance of perhaps eight to ten miles.
It will be seen from the above, that the Tertiaries occupy a great breadth of country on the east coast, having an average width of about thirty miles, and as Hochstetter gives, perhaps somewhat undue prominence to the mountain chain extending N.N.E. from Cape Palliser, and inferentially to the older rocks along the east coast,1 I propose to amend his description of the main ranges, as follows, viz, which stretch along parallel to the east coast, and at an average distance of about thirty miles inland, from Cook's Straits to Hick's Bay, near the Bay of Plenty. This description will leave room for the Tertiaries, and probable Secondaries, which, although forming ridges of an average height of perhaps 1000 feet, or rather more, can barely be called mountainous, nor can they be considered as the continuation of the Southern Alps.
In the southern part of the Island the general character of the Tertiaries is as follows:—
On the eastern side, the upper beds are calcareous—the middle beds are arenaceous and argillaceous.
[Footnote] * Fischer's translation, p. 45.
On the western side, the upper Whanganui beds are arenaceous; the middle calcareous and argillaceous; and the lower argillaceous.
With regard to the Auckland Tertiaries, Hochstetter writes as follows:—“The various Tertiary strata are found for the most part in a horizontal position. A remarkable fact, from which we may conclude that even the numerous volcanic eruptions which took place during and after the period of their deposition had not power enough to dislocate the whole system, but merely to produce local disturbances.”
“The Tertiary period must be divided into two distinct formations, which may perhaps correspond to the European Eocene and Miocene. There is an older formation which is found principally on the west coast and in the interior on both sides of the primary ranges, and a newer one, which may be called the Auckland Tertiary formation.” After a description of the brown coal of the Auckland Province, the same writer goes on to state: “I now come to another series of the older Tertiary strata, examples of which are found occurring in great regularity on the west coast from Waikato to Kawhia. The lowest are argillaceous, the middle calcareous, and the upper arenaceous. The characteristics of the first clayey strata, are a light grey colour, very few fossils, small crystals of iron pyrites, and glauconitic grains, which give these clay marls a similarity to the gault and green sands of the cretaceous formation in Europe. They are found on the eastern branches of Whaingaroa, Aotea and Kawhia harbours.
Of greater interest and importance are the calcareous strata, consisting of tabular limestone, sometimes of conglomerate nature, sometimes more crystalline, the whole mass of which is formed of fragments of shells, corals, and foraminiferæ, interspersed with perfect specimens of terebratulæ, oysters, pectens, and other shells. The limestone when burnt makes excellent lime and may be wrought and polished for architectural purposes.” Beds of limestone in the Wairoa district, as well as rich fossiliferous strata from the Waikato Heads towards Kawhia harbour, also columnar blocks of the same adorning the entrance to Whaingaroa harbour, and the fine caves of the Rakaunui branch of Kawhia harbour, are then described.
“The limestone attains its greatest thickness (from 400 to 500 feet) in the Upper Waipa and Mokau district, between the Rangitoto range and the west coast.”
“The third and uppermost stratum of the older Tertiary strata consists of beds of fine fossiliferous sandstone, in which quarries of good building
stone may be found. There are whole ranges parallel to the Primary mountains which seem to consist of this sandstone. I will mention only the Tapui-wahine range, about 2000 feet above the level of the sea, in which is the pass from Mokau to the Whanganui country.”
“The horizontal beds of limestone and marls, which form the cliffs of the Waitemata, and extend in a northerly direction towards Kawau, belong to a newer Tertiary formation, and instead of coal, have only thin layers of lignite. A characteristic feature of this Auckland Tertiary formation is the existence of beds of volcanic ashes, which are here and there interstratified with the ordinary Tertiary layers.”
“Sandstone and Brown Coal have been found in places to the north of Auckland, in the districts from Cape Rodney to the North Cape.”
I have now, with Hochstetter's assistance, taken a glance at the Tertiary rocks, which occupy so much of the surface of the Island, but, as yet, little has been said of the brown coal, which is found in large quantities, and which, for inland navigation and other economical purposes, promises to prove of great value.
A description of the brown coals of the Auckland province, with several analyses, will be found in Hochstetter's work.1
Besides the localities in the Waikato valley, in which the brown coal is found, it has also been discovered in the direction of the Bay of Islands. In the Wellington province these coal measures are found cropping out in the upper part of the Whanganui river, and some of its tributaries, particularly in the Tangarakau, which takes its rise towards the head waters of the Waitera.
As the Tangarakau seams are found in, or near, the boundary of Taranaki, it is probable that that province also may contain much brown coal.
To the eastward of the main range, a thin seam, about nine inches thick, has been observed in the Hawke's Bay province, and it is not unlikely that good seams of brown coal may yet be discovered on that side of the island.
We may perhaps now consider the circumstances under which these Tertiaries have been deposited.
We find a flooring of Palæozoic rocks generally, perhaps invariably, inclined at high angles, and on this flooring we find the brown coal, with accompanying shales, deposited uncomformably. At the period of deposition of the coal, we must have had dry land for the growth of coal
[Footnote] * Fischer's Translation, commencing at page 18.
plants. After the deposition of the coal, the Island must have undergone depression, and as it sunk, the various Tertiaries must have been deposited above the coal. Not yet, perhaps, did the volcanic eruptions commence, but as the country gradually sunk, and reached its point of greatest depression, the crust of the earth was broken, and streams of basalt flowed over the surface; the depression probably reaching a depth of 1800 or 2000 feet. Nature having completed her work so far, the Island commenced to rise again slowly and steadily, but slightly disarranging the Tertiary rocks on either side of the Island, the volcanic eruptions doubtless still continuing. The Island appears to have rested in its rise at various points, at from 1000 feet to 1200, at 400, 150 to 200, at 15, and at 9 and 4 feet. Various comparatively slight oscillations of level appear to have taken place in recent times, for we find strata of trees, not yet converted into lignite, covered by marine deposits—as between Whanganui and Taranaki, on the Rangitikei river, in Palliser bay, and in places in the Auckland province.1
Thus, after a depression of 1800 or 2000 feet, and the deposition of successive beds of Tertiary strata, the Island rose again, and assumed somewhat of its present form, although probably at the time of emergence it was joined to the Middle Island.
I must not omit a most striking feature of the Tertiaries in the southern part of the Island, in the very broken character which they assume over large areas, notwithstanding their general horizontality. The great Tertiary basin in the interior of the west coast country appears to have formed a series of terraces, gradually rising to the volcanic plateau and chain, and to the Palæozoic ridges; but, whether from contraction, or from contraction, or from the shaking of earthquakes, or from unequal rising of the land, or simply from the wearing away of soft rocks by the action of rain and rivers, each, several, or all of these causes, have cut up the terraces into deep ravines of a very remarkable character.
To give a general idea of the character of the New Zealand landscape, as chiefly affected by its Geological formations, it will be desirable to travel round the coasts of the North Island.
On approaching New Zealand from the westward it is possible that the eye of the traveller will first light upon the magnificent cone of Mount Egmont, forming, with its bold outlying spur, the grand buttress
[Footnote] * Terebratulæ are found in gravel at Cape Palliser, 200 feet above the sea level, and a long rest of the sea level, at a lower elevation, may be inferred from the growth of Pohutukawa trees in certain inland districts of the Auckland province, a tree which only grows naturally on the sea shore.—Thomson, vol. p. 1, 10 and 19.
of Igneous rocks, which protects the great Tertiary basin of the North Island from the encroachments of the waves driven upon the shore by the westerly gales. Mount Egmont forms a regular cone of surpassing beauty, and may be regarded as the Vesuvius of New Zealand. Although hardly possessing the grand features of the great volcanic chain of the centre of the Island, Ruapehu and Tongariro, it has nevertheless a more graceful outline, and its beauty may perhaps be described as of a softer character, the more so, when we consider that the great central chain rises from a plateau of some 2000 feet above the sea, which is swept by cold blasts, and covered by the snows of winter, while the cone of Mount Egmont sweeps gracefully down to the sea level, into fertile plains and low plateaux, which enjoy a genial climate, and are clad in luxuriant vegetation.
The cone of Mount Egmont reaches an elevation of 8270 feet. Its rocks are composed of dolerites and trachytes. Its eruptions have probably ceased since the early Tertiary period; at all events, it does not appear that it has shown any activity since New Zealand has been inhabited.
There is a fanciful tale of the Maoris that Taranaki quarrelled with Tongariro, descended the Whanganui river, and established itself in its present position, but the most fertile imagination can hardly suppose this might refer to the rise of the cone of Mount Egmont, during the “recent” period.
In the neighbourhood of Taranaki are volcanic tuffs, forming cliffs of moderate elevation, and at their base on the sea beach, is found the well-known iron sand of Taranaki, released by degradation from some of the trachytes of the mountain, or its out-lying flows, or other Volcanic rocks along the coast, for the titaniferous iron sand appears to extend, more or less, as far north as Kaipara Heads, and as far south as Whanganui. Indeed small quantities are found still further south, at the Rangitikei and even at the Manawatu rivers, and there are few parts of the Island where its presence may not be detected; this, with siliceous sand, forms dunes on parts of this coast. The Tertiaries in the neighbourhood of Taranaki, are probably very recent. Coasting along to the northward, the Waitara river is passed and the country becomes higher and of a more broken character, the Tertiaries being much fractured and worn into narrow gullies, with an upper surface sometimes flat and sometimes forming sharp ridges. On a clear morning the central volcanic chain may be observed at this point from a short distance in the
offing. Passing onwards towards Mokau, a large area appears to be covered by a tabular limestone of a middle Tertiary age, composed of fragments of shells, corals, and foraminiferœ, interspersed with perfect specimens of terebratulœ, oysters, pectens, and other shells.1
The aspect of the west coast from Taranaki, we may say as far as the Kaipara Heads, or even to Cape Maria Van Diemen, is hilly and broken. The rocks principally consist of marine Tertiaries, viz:—sandstones and limestones, alternating with doleritic and trachytic lavas, conglomerates, and breccias of the same, an occasional volcanic cone (as at Karioi to the southward of Whaingaroa harbour), considerable formations of drift sand forming dunes which reach a height of 500 feet above the sea, and patches of Secondary rocks at the heads of the Kawhia and Whaingaroa harbours.
The coast ranges are hardly high enough to be called mountainous, but almost too high to be described as hilly.
The sand dunes appear to a great extent between the Waikato and Manukau Heads, and also at some points to the northward of the latter, but the country north of Auckland has never to my knowledge, been systematically described.
It appears, however, that this district shows in places a flooring of Palæozoic rocks, and a large proportion of marine Tertiaries. Secondary rocks are said to occur in the harbour of Hokianga to a limited extent. Limestones and calcareous sandstones are found profusely distributed in the Kaipara harbour, of which the age is undetermined, but they are probably Tertiary. Coal, of which the beds appear to be of considerable thickness, is found to the northward, and at the Bay of Islands appears to be of good quality, whatever its geological age may be.
The northern Peninsula is dotted over with numerous volcanic cones, and other remains of igneous action. The range which runs from Cape Rodney to the Kaipara harbour, on the ridge of which the escaped Waikato prisoners have built their “pa,” seems to be mostly composed of tufaceous materials, frequently arranged in spheroidal concretions. Similar rocks are found at Matakana and near Mahurangi, not far from which (at Waiwera) are hot springs.
At Wangarei North Head, are the remains of a magnificent crater, which formerly may have included the “Hen and Chickens” group of Islands, either as one gigantic crater, or as a series of cones forming a volcanic chain. Almost all of the old crater wall is now broken down
[Footnote] * See Hochstetter, Fischer's Translation, page 25.
and has disappeared, but, part of it I think may still be made out from inland of the Heads. Many first and second-class harbours indent the northern peninsula. The Palæozoic rocks of the “Barrier” on the left contrast with the more tame outline of the Tertiary landscape on the right.
Certainly the approach to the Waitemata harbour is very beautiful. The Hauraki gulf is dotted over with islands of all sizes; and being of various geological formations, they are in consequence of varied and picturesque outline. Those of tertiary formation, or of older rocks capped by Tertiaries, are of a low horizontal character. Those composed of Palæozoic rocks are bold and angular in outline, while the regular cone of Rangitoto guards with its hard volcanic rocks the entrance to the Auckland port.
There we find a great extent of the later Tertiaries, forming low cliffs along the coast, while the Isthmus of Auckland is found to be a crowded group of small volcanic cones. The decomposing rocks of this volcanic series form the richest soils of the north, and the slopes of these volcanoes are covered by fertile fields.
Passing round the Frith of the Thames, we find Palæozoic rocks on both sides, with low lands of alluvium and swamp in the interval. Thence passing between the mountainous country at Cape Colville, and the great Barrier Island, is found a tract of country of Palæozoic, flanked by basaltic rocks; and turning to the southward we pass along by the high Coromandel ranges, which attain a maximum elevation of 2700 feet, until we find ourselves trending to the eastward along the low shores of the Bay of Plenty, a large part of which presents to the sea a low swampy shore,1 with basaltic or trachytic rocks at various points, as at Okura and Matata. Approaching Whakatane, the long and lofty ridges of the Palæozoic rocks of the main ranges may be perceived coming up from the S.S.W., possibly invaded by some eruptive rocks, and amongst them, as Hick's Bay is approached, the high peaks of Mount Ikurangi, 5533 feet above the sea, show well out in the interior, and indicate an apparent volcanic or, to say the least, a trappean appearance for that mountain. About eight miles from the East Cape, at a place called Kawakawa, rocks, evidently of Tertiary age, and with cliffs much resembling those of the Whanganui river, appear abutting on the Palæozoic rocks. Their highestelevation is about 400 feet. Passing the East Cape, we find apparently the same Tertiaries, with possible Secondaries, all the way to Table Cape
[Footnote] * Hochstetter's Map.
and Portland Island; but this country has never been geologically examined. The interior, as seen from the sea, is much broken, and the long ridges of the Palæozoic ranges may generally be seen, some twenty or thirty miles inland. Between the Terakaka Peninsula and Napier, besides the marine Tertiaries, there is also said to be a good deal of drift pumice in places. Arriving at Napier, we find a Peninsula of new Tertiary limestone, rising to a height of several hundred feet, and forming a centre to long boulder banks on both sides. That on the northern side forms a protection to the inner harbour.
From the southern boulder bank the Ahuriri Plains sweep into the interior to join the plains of the Rua Taniwha, which are continued by the terraces of the Forty Mile bush to the Wairarapa Plain and to Palliser Bay.
Passing round the shores of Hawke's Bay we find the Tertiary limestones, sandstones, mudstones, and clays forming cliffs towards Cape Kidnapper; they dip slightly to the westward, and therefore it may be supposed that certain lines of trappean dykes, which are found further south, near Flat point, and elsewhere, here pass out diagonally seaward, and that their intrusion has caused the tilting action which will account for the westerly dip. At Cape Kidnapper there is some reason to suppose that the hydraulic limestones, of probably Mesozoic age, may be found lying uncomformably below the Tertiaries. From Cape Kidnapper, on a clear day, Ruapehu may be seen, but Tongariro and Ngauruhoe are hidden by the intervening ranges. Hence the Ruahine range shows out strongly and sharply, covered by snow for many months in the year. Passing to the southward from Cape Kidnapper, we skirt a range of calcareous and sandstone rocks, the probable Secondaries, rising to an average elevation of about 1000 feet, and preserving a monotonous sameness of character and outline. They hide the higher and more picturesque ranges in the background. At Castle Point, a small harbour is formed by a reef and peninsula of Tertiary limestone, with Pecten Burnettii, and here also certain sandstones and mudstones are found containing undefined impressions of plants and small seams of coal. Along this coast, and more particularly between Flat Point and Pahaoa, the hydraulic limestone series is met with, which may possibly be of Mesozoic age. At Waikekino, six miles south of Flat Point, reefs of Amphibolite are found on the shore and in the sea, penetrating the above-named calcareous rocks, and boulders of various trappean rocks are common in the Kaiwhata and other rivers. Passing to the south of the Pahaoa river, Palæozoic sandstones
and slates appear, with jasperoid rocks, and these continue round the bold buttress-like headland of Cape Palliser.
Proceeding round the abrupt and rugged country which lies behind Cape Palliser, we reach the level plain of the Wairarapa valley. An inland plain, of about ten miles broad, which passes up between the Rimutaka and Tararua ranges on the left and the lower slope of the Tertiary ranges on the right, continues with a similar width through the Forty Mile bush to the eastern Manawatu, thence to the Rua Taniwha plains and then turns seaward to Napier. An old Fjord, or possibly two separate arms of the sea, which formed gravel terraces, now offers an admirable line of communication between Wellington and Napier. In Palliser Bay the cliffs are from 50 to 150 feet high, composed of “drift” gravel on the western side, of gravel over blue clay on the eastern. Passing across Palliser Bay we arrive at the highly inclined rocks of the main range, cut off and scarped along this south coast, and at the Muka Muka are found trappean rocks, altering the slates into jasperoid rocks. At this point also was the greatest rise of land caused by the earthquake of 1855 (viz., 9 feet), and here the coast road which was before that time almost impassable, except at low tide, has now a broad stretch of rooky beach between it and the sea.
Proceeding to the westward along the south end of the Island, we continue to pass the vertical scarp of the rocks, caused by the great depression of Cook's Straits. The strata being highly inclined, and the mountains forming remarkably sharp ridges, rising to a height of from 2000 to 3000 feet, and running in a N.N.E. direction. Looking up the noble harbour of Port Nicholson, the alluvial valley of the Hutt may be perceived, forming the only great longitudinal valley of the mountain ranges. Proceding onwards, we may find the same evidence of the intrusion of Igneous rocks as at the Muka Muka, and may also perceive small patches of drift gravel, lying at various elevations from 400 feet downwards; from the position of these terraces we may, I think, conclude that they were formed previous to the depression which formed Cook's Straits. At Terawiti instead of passing along the great scarp at right angles to the strike of the rocks, we now proceed to the northward in their line of direction, and as we look into the harbor of Porirua we may think of the “plant beds” there, a further investigation of which may perhaps lead to a clear history of the age of these rocks. On the left we leave the flat topped island of Mana (Palæozoic), and pass on to the junction of the Tertiary and
and Palæozoic rocks, near Paekakariki, and here the great Tertiary basin commences. From this point the ranges of the old rocks pass away inland towards the N.N.E. while the Tertiaries, commencing the great western curve towards Cape Egmont, are as yet only represented by dunes of sand. Eight miles further on we reach Waikanae, opposite to which is the high Palæozoic island of Kapiti which forms a shelter from the prevailing westerly winds. In consequence of this protection the Waikanae river throws out a long point seaward. At Otaki, in addition to the sandy dunes, there is a considerble breadth of “drift” gravel formation, and also here and along this coast, there is much alluvium and swamp. At the Manawatu river, the sandhills which sometimes reach a height of from 40 to 50 feet, attain their greatest breadth, of about ten miles, and are intermixed with some rich tracts of swamp and alluvium. Inland of this, the “drift” gravel forms terraces, and what appears to be the blue clay shows itself a few feet above the river level, the mountains having receded to a distance of 25 or 30 miles from the coast. The coast now trends rapidly to the westward, fringed by sandhills, behind which may be seen the fertile country composed of Upper Tertiaries. Passing the low ground at Rangitikei the coast rises into cliffs towards Whanganui, of from 100 to 200 feet high. The bold outline of Ruapehu may now be seen overlooking the great Tertiary basin, and covered with snow, to the north of Whanganui. The ridges of Ruahine stretching to the N.N.E. are far in the distance, while to the westward the graceful cone of Mount Egmont also comes into the general view. Between Whanganui and Kai-iwi an “old forest” is found in the cliffs, and numerous remains of Moa in the sandhills above. Between this and Taranki the grand curve of the coast shows Tertiary cliffs to the sea, the upper beds of which appear to be very recent. This part of the coast has not yet been examined and it is more than probable that the basalts or other Igneous rocks may be exposed at different points on the coast and to the inland of the mountain. With this exception, the interior country here appears to be entirely composed of sedimentary Tertiaries, with the grand cone of Mount Egmont rising like an island from their midst.
The Volcanic system of the North Island is comprised within certain limits, as follows:—If we draw a line from the southern base of Mount Egmont and continue it past the southern base of Ruapehu until it approaches the Kaimanawa range—then by striking a line nearly at
right angles from this point to the mouth of the Whakatane river, in the Bay of Plenty, we shall find the whole country to the north and north-west, as far as the North Cape, more or less dotted over with volcanic cones. Certain trappean dykes are found in districts to the southward and eastward of these lines, but no true volcanic craters, unless possibly Mount Ikurangi, previously mentioned, may prove to be one.
With regard to the volcanic part of the Island, Hochstetter states as follows:—“Lofty trachytic peaks covered with perpetual snow, a vast number of smaller volcanic cones, presenting all the varied characteristics of volcanic systems, and a long line of boiling springs, fumaroles and solfataras, present an almost unbounded field of interest, and at the same time, a succession of magnificent scenery.”
“The first volcanic eruptions were sub-marine, consisting of vast quantities of trachytic lava, breccia, tuff, obsidian and pumice stone, which, flowing over the bottom of the sea, formed an extensive submarine volcanic plateau. The volcanic action continuing, the whole mass was upheaved above the level of the sea, and new phenomena were developed. The eruptions going on in the air instead of under the sea, lofty cones of trachytic and phonolitic lava, ashes and cinders were gradually formed. These eruptions breaking through the original submarine layers of trachytic lava, breccia and tuff, raised them and left them, as we now find them, forming a more or less regular belt round the central cones, and having a slight inclination from the centre outwards. These belts I shall have occasion to refer to under the name of ‘tuff craters,’ or ‘cones of tuffs,’ or ‘craters of elevation.’ In the course of time the volcanic action decreased, and we must now imagine that tremendous earthquakes occurred, that parts of the newly formed crust gave way, and fell in, forming vast chasms and fissures, which are now occupied by the lakes, hot springs, and solfataras.”
“Thus we now find in the central part of the Northern Island an extensive volcanic plateau, of an elevation of 2000 feet, from which rise two gigantic mountains—Tongariro and Ruapehu. They are surrounded by many smaller ones, as Pihanga, Kakaramea, Kaharua, Rangitukua, Puke Onaki, Hauhanga. The natives have well-named these latter—‘the wives and children of the two giants Tongariro and Ruapehu’—and they have a legend to the effect that a third giants, named Taranaki, formerly stood near these two, but, quarrelling with his companions about their wives, was worsted in combat, and forced
to fly to the west coast, where he now stands in solitary grandeur, the magnificent snow-capped beacon of Mount Egmont (8270 feet). These are the three principal trachytic cones of the Northern Island.”
“By far the grandest and loftiest of the three is Ruapehu, whose truncated cone, standing on a basis of about twenty-five miles in diameter, attains a height of 9000 to 10,000 feet above the level of the sea, about 3000 feet of which is covered with glaciers and perpetual snow. Ruapehu, like Taranaki, is extinct; Tongariro can alone be said to be active. I was enabled to distinguish five craters on Tongariro, three of which are, to a certain extent, active. Steam is always issuing from them, and the natives state that from the principal crater, called Ngauruhoe, on the top of the highest cone of eruption (6500 feet), occasional eruptions of black ashes and dust took place, accompanied by loud subterranean noises.”
To this description I will add that Tongariro appeared to me to be a truncated cone, of which the main crater had fallen in, and had probably at one time exceeded Ruapehu in height. Ngauruhoe rises from its flank as a lateral cone.
The plateau under the eastern side of Ruapehu is called Onetapu, or sacred ground. The wild appearance of this tract is well described by Dieffenbach. Here the trees, principally birch and totara, are dwarfed from the elevation, and the ground is scarred by the washing of torrents, or from the effects of winter frosts.
From the eastern base of Ruapehu the river Wangaehu rises, as a stream of water, said to be charged with sulphurous acid as well as other mineral compounds. All along the base of the volcanic chain similar springs may be found, until on arriving at Tokanu, on the southern shores of Lake Taupo, the delta of the Tongariro river is found honeycombed by hot springs, and long lines of the same may be seen extending up the side of the hill overlooking the smothered village of Terapa, where the venerable Te Heu Heu, and many of his tribe, met their death by the slipping of the side of the mountain in the year 1847.
It would occupy too much space in an essay of this kind to enter into a description of the grand system of hot springs, warm lakes, mud springs, and other volcanic phenomena, which are found in this country, extending from Lake Taupo to the Bay of Plenty, and thence to White Island. For a description of these, the reader must be referred to Hochstetter and other authors.1
We may now proceed to consider the Igneous rocks in the southwestern or trappean part of the Island, as previously indicated.
These rocks are only to be perceived at a few points, apparently forming dykes in, or nearly in, the line of direction of the ranges. Thus Amygdaloidal Trap may be perceived traversing Palæozoic rocks at Muka Muka, and Amphibolite, traversing calcareous rocks of a newer age at Waikekino, on the east coast of the Wellington province.
Terraces and Raised Beaches.
These form a characteristic feature of New Zealand Geology. Pumicestone terraces are found fringing the volcanic chain at an elevation of about 2000 feet, and also occupying large areas in the Province of Auckland at a lower elevation.
Terraces at the south part of the Island are found, as previously stated, at about 1000 feet, 400, 250 to 300, and decided raised beaches at about 15, and 4 to 9 feet. That these extend throughout the Island at similar levels is probable, but more information is wanted to establish this fact.
Between these principal terraces are many smaller ones. Although fossils are in general absent, it is likely that the terraces mark successive rests of the land during its rise. To account for them as lake terraces would require the supposed erection, or rather demolition, of a vast number of barriers.
At a height of about fifteen feet above the present sea level a very well defined sea beach is found all along the southern coast, worn into cavities, and bored by the shells of Pholadœ. The latest raised beach is that which marks the rise of the land during the great earthquake of 1855. This upheaval appears to have been greatest at the Muka Muka rocks—nearly nine feet—and is supposed to have sloped off to nothing at the Manawatu; but, although the coast may not have risen at the latter point, there is no evidence that the interior ranges were not lifted, and they certainly show signs of having been thrust through, and having partially lifted the Tertiaries, either at that time or at some former period, or to have oscillated upwards on the eastern side with a pressure at the same time against the west coast Tertiaries. In the southern part of the Island the chief gravel formations extend from Palliser Bay up through the Wairarapa and Forty-Mile Bush towards Napier; next on the west coast from the Waikanae river to the Rangitikei and Whanganui rivers, capping the Tertiary sandstones of the interior,
where undenuded. At the south-west corner of the Wairarapa valley, the higher drift is found to rest unconformably upon an older formation of gravel and lignite.
Gold has been found at various points in the North Island, and it may almost be said that all the Palæozoic rocks show its presence. It has only been worked, however, to any extent at Coromandel.1 From Coromandel and from the Palæozoic rocks on the western side of the Frith of the Thames it is possible that gold may be found to extend up the valley of the Thames, wherever the old clay slates may be exposed, but whether in the shape of quartz reefs, or of alluvial gold, remains to be proved.
Specimens of auriferous quartz have been procured from the Hangawera range, which separates the valley of the Thames and the Waikato, and this indicates the line along which the precious metal may be sought for. The Kaimanawa range has never been examined. Some specimens of galena and other metallic ores, brought in by the natives to Hochstetter's party, are said to have come from it, and there is a strong probability of its rocks having an auriferous character, lying as it does in the continuation of a probable line of strike from the gold bearing rocks of the Pelorus district.
The great mass of Tertiaries which covers the interior renders the search for gold difficult and uncertain. A small quantity has been procured from some of the gullies in the neighbourhood of Terawiti, near Wellington, and it seems probable that the pyritous slates, or veins, of the ranges there may be more or less auriferous.
Any remarks on the Geology of New Zealand would be deficient if they did not refer to the numerous earthquakes by which this group of islands has been visited.
It may be decidedly assumed that there are certain long lines, or segments of circles, along which, either from the weakness of the earth's crust, or from other causes, volcanic eruptions are most prevalent, and the action of subterranean forces are prominently shown by earthquake shocks.
The New Zealand group is situated on one of these lines, the southern
[Footnote] * Total exported to 31st December, 1864, 9,584 ozs., value £22,875.—Ed.
known limit of which is the land where Mounts Erebus and Terror raise their lofty volcanic peaks amidst Antarctic snow and ice. From these mountains the trend of the curve may be said to pass through New Zealand, and other oceanic isles to New Guinea (appearing to conform to the shape of the eastern coast of Australia), and thence through a long chain of eastern islands to the Straits of Sumatra. The experience of twenty-four years is insufficient to form very decided opinions on the character or locality of the earthquakes of New Zealand. Nor indeed is there sufficient knowledge of the causes at work to be able to predict where or when an earthquake may break out. Reasoning on the subject is useless, from want of sufficient data. Along the analogous volcanic line of South America earthquakes are of constant occurrence. One day they will break out at Concepcion, the next shock will be felt at Lima, then at Valparaiso, at Islay, at Guayaquil, and two years ago the action appears to have shifted to the city of Mendoza, on the eastern side of the Andes, where earthquakes had been hitherto unknown. The changes going on from time to time in the great area of depression of the Pacific, may be reasonably supposed to act with notable force on the eastern and western edges of the basin, whether in America, or in New Zealand and its continuing curves.
The severest shocks of earthquakes that have been felt in New Zealand since the arrival of the Settlers, took place in 1843, in October 1848, in January 1855, and in February, 1863. These three latter shocks appear to have been felt more or less, over, at all events, a large part, if not the whole, of the islands, but no systematic attempts have hitherto been made to record earthquake shocks throughout the Colony. The three former ones were most severe in Cook's Straits—the last at Napier. The greatest force of the earthquakes of 1848 and 1855 appears to have been exerted near the Kaikoua mountains, in the Middle Island. Wellington suffered severely from the earthquake of 1848, and that of 1855 raised the land in its vicinity to a height of from nine to four feet above its former level. Nelson felt both shocks perhaps less severely than Wellington. The impression is that during the earthquake of 1855, while the land at Wellington rose, that on the south side of the Straits was depressed, and of this there appears to be good evidence. The earthquake of 1863 was felt severely in some parts of the Hawke's Bay province, and considerable local changes of level there appear to have taken place. A description of several of these earthquakes may be found in Taylor's work, page 226 et seq.
The natives have traditions of many earthquakes having happened before the arrival of the settlers.
Earthquakes are generally looked upon as the manifestion of a destructive force, whereas, if rightly considered, they indicate a great conservative power, which balances the relation of land and water on the surface of the globe, and it may not be out of place to remark, that in many countries subject to their effects, we find the ancient seats of civilization. In the East we find these, in China and Japan, in India and Mesopotamia, all earthquake countries. In Europe and Africa the old haunts of arts, science and philosophy: Egypt, Greece and Italy, are earthquake countries. In America the highest civilization to which the old race attained, was reached by the Aztecs of Mexico, and the subjects of the Incas of Peru, both races inhabiting earthquake countries “par excellence” of the American continent.
The most fertile lands of the Southern Hemisphere are those which are, and have been, subjected to great igneous and earthquake action, and the varied outline, and in consequence the well watered and fertile lands of New Zealand, might be disadvantageously exchanged for the broader, and more level, less earthquake shaken, but arid expanse of the Australian plains.
The present information as to earthquakes in New Zealand may be summarized as follows:—
Mr. Edward Weller felt shocks of very great force in Stewart's Island, in the year 1833, and it is probable, that there may have been many shocks since that time.
Mr. W. Mantell collected information from the Maoris, that very severe shocks had formerly been felt in Otago.
The earthquake of 1855 was marked in this latter province by a great sea wave, and since then various slight shocks have been felt at different times by the settlers.
In Canterbury the information with regard to earthquakes is imperfect, but many minor shocks have been felt, and the earthquake of 1855 was felt severely.
In Cook's Straits earthquake shocks have been more numerous than elsewhere since the settlers arrived. The severest shocks, as before stated, were in the years 1848 and 1855. At Taranaki shocks have been very numerous, and some of them tolerably severe. At Napier the shocks latterly have been more severe than elsewhere, and at Auckland
many minor shocks have been felt, with a few of rather decided character.
Comparisons with Middle Island.
It is a point worthy of note that the vertical oscillations of the two great Islands of New Zealand seem to have differed very much, both in time of occurrence and in degree. In the North Island the depression in Tertiary times would appear to have been much greater than that of the Middle Island. At all events, if not greater in amount, it must have affected the character of the Island to a greater degree, from its much smaller elevation, and consequent greater submergence.
In the North Island the greatest depression seems to have been on the western side, while in the Middle Island the reverse was probably the case.
In the North Island the Tertiaries occupy a far greater area than in the Middle Island, which alone would tend to show, a longer and greater depression. Glacial action must have had much less effect in the North than in the Middle Island, irrespective of difference of latitude, for two peaks only in the former Island now carry perpetual snow, viz:—Ruapehu and Mount Egmont, and at no Tertiary time could the mountain masses have equalled those of the latter Island.
Aerolites have been frequently seen in New Zealand. It is believed, however, that the only one which has been found on the surface of the country, is that which will be now described.
It was found in the year 1863, in front of Mr. Donald's house, at Manaia, near the left bank of the Wai Ngawa river in the Wairarapa, province of Wellington, the plain is here composed of coarse gravel. The aerolite was found on or near the surface, and meassures 9 in. × 6 in. × 7 in.
A portion of this interesting specimen was forwarded for examination to the Laboratory of the Otago Geological Survey, at Dunedin, and the following notes respecting its composition have been furnished by Dr. Hector.
“The fragment submitted for analysis was externally of a rust colour with an exudation of chloride of iron. The freshly fractured surface was of a dull grey colour. Its hardness was between—5 and—6, and its specific gravity 3.254. It is affected by the magnet, but does not exhibit
polarity. It consists principally of earthy silicates and sulphide of iron, but also contains nickel and native iron, and possesses the general character of a Meteoric Stone.”
The direction of the prevailing winds is well shown in the North Island by the fact of sandhills being almost entirely confined to the west coast, and wherever the shores are sufficiently low the sand on that coast travels inland and forms dunes. Where the coast trends north and south, with the above conditions, the sand travels far into the interior. Where the coast line runs east and west the sand blows along it, and does not reach far inland.