A Voyage of Discovery and Research in the Southern and Antarctic Regions/Volume 2/Appendix 3
APPENDIX, No. III.
GEOLOGY OF NEW ZEALAND. BY ROBERT McCORMICK, ESQ., SURGEON OF H. M. S. EREBUS.
My observations on the geological structure of this new colony were limited chiefly to the northern portion of the North Island, the Bay of Islands, and its vicinity.
The bay, perhaps, the finest harbour in New Zealand, is studded with several islands, and has its shores bounded by argillaceous cliffs of moderate height. The clay of which these are composed is of a yellow colour, variegated by a reddish tint, and rests upon a substratum of trappean rocks, fragments of which, more especially greenstone, frequently occur imbedded in it. A low tract of prismatic basalt, intermingled with scoriæ and greenstone, extends between the Waitangui and Kiddi-Kiddi (or, as it is also called, Keri-Keri) rivers. This, doubtless, has been a lava current, the source from whence it flowed being pretty clearly indicated by a conical crateriform hill, situated at no great distance inland of it. Several rivers fall into the bay, whose shore is intersected by numerous ravines, creeks, and mangrove swamps, Manawa (Avicennia tomentosa). Whilst the Expedition remained in the bay, the Manuka, or tea shrub of the New Zealanders (Leptospermum scoparium) was in full flower, and lent a cheerful appearance to the sides of the hills, over which it was spread in profusion; the paths of the natives leading in an intricate maze of windings through it around every neighbouring hill. That beautiful tree the Pohutukava (Metrosideros tomentosa) was just beginning to put forth its rich crimson blossoms, amid a deep green clustering foliage; and it appeared to be the favourite station of the Kotaritari, a small kingfisher (Alcedo cyanea), whilst watching for its prey in the waters beneath.
In an excursion to Waimate, a missionary station, about fifteen miles inland of the bay, my course lay over hills about seven or eight hundred feet in height, crested with trees, or clothed with fern (Pteris esculenta),—once constituting the main subsistence of the natives,—and intersected by deep and densely wooded ravines. On crossing the second range of hills, I came upon the fern-clad plateau of the Waimate, and made a detour to the left, to examine some limestone rocks, cropping out from the bed of the Waitangui River, which is here about thirty feet wide; and the current setting so rapidly round the sharp curve it makes between its steep and wooded banks, that the horse I rode lost his footing, and had some difficulty in stemming it, whilst I chipped off specimens from two highly crystalline blocks of white marble, rising four or five feet above the centre of the stream, which ran S.W. and N.E.; the strike of the bed of limestone being E.N.E. and W.S.W., but no discernible dip.
On the approach to Waimate, emerging from a narrow belt of wood, ornamented by a large graceful tree-fern, the settlement, with its neat new church, farms, and houses enclosed in flower-gardens, having a thoroughly English aspect, all at once burst upon the view, amidst the surrounding fern-clad region, like an oasis in the desert. The decomposing greenstone in the vicinity presents a globular jointed structure, spherical masses of which, resembling cannon-balls, lay scattered about the surface of the soil, near a forest of the Kaudi pine (Dammara Australis), the only cone-bearing pine in the island, and confined to its northern part, where the stiff clayey soil seems favourable to its growth; it is mostly found in hilly situations, in the vicinity of the sea, usually with a quantity of its yellow transparent resin (pare) imbedded at its base. The thirty-eighth degree of south latitude is about the limit of its geographical range.
Ten miles from Waimate, I ascended a truncated cone-shaped hill, terminating in the most symmetrical and perfect crater I have ever seen, forming a circular bowl, nearly 300 feet in depth, and much about the same in diameter, strewed over with fragments of scoriaceous lava, basalt, and greenstone, and densely lined with trees and tangled underwood, through which, after some little difficulty, I scrambled to the bottom; where the almost death-like solitude of the scene was broken only by the melodious note of that elegant and singular bird, the Tui (Meliphaga concinnata), which, like the American mocking-thrush, imitates the notes of every other bird in the forest.
On one side of the hill is a steep ravine, which once gave exit to the lava current, but is now separated by an embankment of scoriæ, which here completes the rim of the crater. Numerous ancient native "pahs" crest the neighbouring hills.
About a mile to the north of this once volcanic vent, which has long been in a state of repose, are some thermal springs, forming small pools in a level tract of scoriaceous lava, overgrown with rushes, from which sulphuretted hydrogen gas rose in bubbles to the surface; the grass on the margin was incrusted with a deposit of sulphur, yet the water is not unpleasantly impregnated with it.
Some miles distant are a lake and hot springs, which my time did not permit me to visit. On my return to the bay, I passed the Waitangui Falls, forming a pretty little cascade over basaltic rocks into the channel of the river beneath, where it sweeps round a sandy cove, not far from its exit into the bay. From this waterfall the river receives the name of Waitangui, meaning in the Maori, or native language, "crying, or weeping waters."
In a boat excursion I made up the river Kiddi-Kiddi, I found the banks composed of the same kind of argillaceous deposit resting on a trappean basis, as on the shores of the bay. About six miles up, the stream divides into two branches; I followed the one to the left, on the right bank of which a bed of pipe-clay (kotare), twelve feet in thickness, striking S.E. and N.W., crops out from columnar greenstone.
At the missionary station I landed, and crossed over a platform of fern for about two miles to the Keri-Keri falls, which descend over a perpendicular escarpment of basalt eighty or ninety feet high into the ravine below: this is scattered over with fragments of rock, and its banks finely wooded, between which the river continues its winding course. Behind the cascade, and beneath the basalt, is a cave nearly a hundred feet wide, about forty deep, and much the same in height, from which the spray of the falling waters (termed by the natives waianiwaniva, or rainbow-waters), produces a pretty effect, forming a complete curtain of mist in front of the cavern, the roof and floor of which are crusted over with ochraceous clays of various colours. The red ochre (kokowai), and the blue (pukepoto), are used by the natives to paint their skins. On rounding the point at the entrance of the river, on my return to the bay, in the dusk of the evening, the splash of the boat's oars breaking on the silence of nightfall, disturbed a whole colony of cormorants (Phalacrocorax), the kauwau, or preachers of the natives, who had built their nests on the tops of a group of trees, over which they hovered in the wildest confusion and uproar.
In a boat excursion on another occasion, up the river Kawa-Kawa, or Bitter-Bitter, the main continuation of the bay, I landed on the left bank, and proceeded over about four miles of a fern-clad table land to the valley of Waiomio, where some remarkable groups of marble crop out from the adjacent hills of greenstone, to the height of from ten to about forty feet, in castellated forms, like ancient ruins, grown over with trees and shrubs, and occupying a somewhat irregular circle, having the same general bearing, E.N.E. and W.S.W., as the Waitangui marble. Most of the masses were white, hard, and crystalline, having sharp and angular edges, with a blackened surface, and horizontal stratification. One group was of a reddish yellow colour, and of coarser grain than the rest. As I was about ascending the highest group, my steps were arrested by a chief much tattooed, who suddenly emerged from the wood, and gave me to understand that the place was "tapu," or forbidden ground, being the "warau," or burial-place of his tribe, who inhabited the village of Waiomio, on the banks of the river which meanders through the valley beneath, in a S.E. and N.W. course.
As the boat passed the missionary station on the Kawa-Kawa, I observed something suspended in the air like a hawk hovering over its quarry; but which turned out to be a kite, the flying of which is here an amusement of the Maori children. It is most ingeniously made from the leaves of a species of Cyperaceæ, or sedge, with wings resembling a bird, from which it receives the names "manu," a bird, or "paku," wing of a bird; the Phormium tenax furnishes its flaxen string.
From the foregoing remarks on the northern part of the island, it will be perceived that New Zealand has a volcanic substratum of basalt and greenstone, with a superincumbent deposition of clay, through which beds of limestone and sandstone crop out in various places. The limestone cliffs at Waingaroa Bay contain fossil shells of the following genera: Ostrea, Pecten, Terebratula, and Turritella, with Asterias and Echinus: the neighbouring sandstone being much interrupted by greenstone dykes. Layers of lignite are found in beds of loam. This carbonised wood, which is said to have belonged to Kaudi and Pohutukava trees, is abundantly distributed, both on the east and west coasts, especially in the valley of the Thames, associated with horizontal sandstone formations near Auckland. Copper ore, in micaceous slate, has also been found in this locality. Fossil shells occur in the vicinity of Poverty Bay. The Green Jade, or a variety of serpentine, of which the Meri, or native club, is made, is found only in the southern island, and is much valued; it is called Ponamu by the New Zealanders.
Cape Maria Van Diemen, the north-western extremity of the island, is composed of a volcanic conglomerate; in the vicinity of which is the Reinga, or entrance to the New Zealanders' world of departed spirits, which they suppose to be down a steep escarpment of conglomerate rock, overhung by an aged Pohutukava tree, from which the spirit is said to take its final flight to the region below. This sacred spot is the Land's End of the natives, "Te muri wenua." Coal has been found in the sandstone, overlaid by this conglomerate, but to no great extent.
Fossil bones of a large extinct struthious bird, known to the natives by the name of Moa, have been discovered in the alluvium of the mountain streams of Hikorangi on the east coast. It has received the name of Dinornis gigantea, and its height has been estimated at sixteen feet: remains of several smaller species have been also found.
Its only existing type is the Kiwi Kiwi, or Apterix Australis, a bird now becoming very scarce, and, like its gigantic predecessors, destined to become extinct. The natives formerly hunted it for its feathers, of which they made beautiful mats: but since the introduction of the dog and cat, its destruction has been rapidly accelerated; and, as it lays only one egg, its total extirpation cannot be far distant. It is a nocturnal bird, burrowing in the ground during the day, and wandering about the deepest recesses of the forest in the night, in search of the larvæ of insects, and seeds of a rush (Astelia Banksii), its favourite food. It is now mostly met with in the locality of the East Cape.
The principal mountains in the interior are Ruapahu, rising to the height of 9000 feet above the level of the sea, Taranaki, or Mount Egmont, to about 8800, and Tongariri, to somewhat more than 6000 feet. The latter is the great centre of volcanic action, and has a large crater on its summit, sending forth smoke and steam, and from which eruptions of lava not unfrequently take place. Pumice, obsidian, and porphyry are abundantly distributed about this district. Hot springs (pui) are numerous; some have an argillaceous, others a sulphureous taste, and often a boiling temperature, accompanied by continuous subterranean sounds. Cold saline springs occur near the hot ones. Shocks of earthquakes, termed by the natives "Wiringa O te Wenua," or, trembling of the land, are occasionally felt. Ruapahu is even in summer covered with perpetual snow, the snow-line being here at an elevation of about 7000 feet. A chain of lakes extends through the interior. Taupo, the largest, is thirty-six miles long, and twenty-five broad, of a triangular shape, encircled by high cliffs, and situated in 39° south latitude, and 176° east longitude, at an elevation of 1300 feet above the sea, and Lake Rotu Aire at 1700 feet. On White Island (Puhia-i-Wakati) there is also a volcanic vent, sending forth smoke and vapour. Raised beaches occur on the coast, indicating here, as in Tasmania, an upheaval of the land.
The climate of New Zealand is so fine and equable, that the mean annual temperature falls little short of 60° Fahr. It is humid, as might be expected, in two narrow islands, 800 miles in extent, covered with forests, and on all sides encompassed by a vast ocean. Northerly winds prevail in winter, and the southerly in summer.
In the month of November, "Marama-ko te-ono," or sixth month of the New Zealanders, I found the nights so mild, that having on one occasion extended an excursion inland from the bay, to a greater distance than I had anticipated, in search of that beautiful species of pigeon, the Kukupa (Columba Novae Seelandiæ), which conceals itself in the deepest recesses of the ravines, feeding on the berries of the liands (Smilax), and other seeds, and where it is most difficult to find, night closed in upon me, before I could retrace my steps through the many dense thickets of wood, and hills of high fern, which lay between me and the anchorage of the ships; and I slept in the open air, without sustaining any other inconvenience than that of being awoke somewhat early in the morning by a shower of rain, with no other covering than some withered clematis, the fern being wet with the dew. The beautiful white flowers of the clematis appeared suspended in graceful festoons from the tops of the highest trees.
I, however, had no reason to regret passing the night in the woods, as I not only succeeded in shooting some pigeons, but it afforded me a fine opportunity in my favourite pursuit, ornithology, for observing the habits, and making myself acquainted with the notes of the various species of the feathered tribe. The bottom of the ravine, on the margin of which I passed the night, was brilliantly illumined by phosphorescent particles, which glittered like so many glow-worms, or fire flies, in the decaying wood. Over head, the Peka-peka, a small bat (Vespertilio tuberculata),—the only mammal in the country, with the exception of the native rat (kiore maori), which is now become nearly extinct—silently wheeled in circles above the wood, and in the topmost branches of a tree, the Ruru-ruru, a small owl (Strix Novæ Seelandiæ), kept up its incessant monotonous cry of "More-porke, more-porke," throughout the night. At dawn, I heard the voices of the natives, mingled with the barking of the dogs, and crowing of the cocks in a village, from which I found that I had been separated only by a Raupo swamp below me, overgrown with the typha, or bullrush, the favourite haunt of the Matuka, or Bittern (Ardea Australis), the Pukeko (Porphyrio Australis), and the Parera, or wild duck (Anas superciliosa). The latest bird in the evening was the Piwaka-Waka, an elegant little flycatcher (Rhipidura flabellifera), and the earliest in the morning was the Tui.