THE SOUTHERN ISLANDS

New Zealand Times, Volume XXIX, Issue 6383, 4 December 1907, Page 9

THE SOUTHERN ISLANDS

INVESTIGATIONS BY SCIENTISTS,

THE HINEMOA EXPEDITION

GEOLOGICAL RESULTS.

(By R. Speight, M.A.,.8.5c., Lecturer on Geology at Canterbury College.)

In a former article on the Southern Islands of our Dominion, published iu the “New Zealand Times'’ before the departure of the Hincmoa, I gave a sketch of what was known up to the present of their geological history. I pointed out that very little was definitely known about them, and that many contradictory and misleading statements had been made. 1 think that when tho results ol this expedition are fully worked out a Hood of light will bo thrown on their geolo<’\-, and though much remains yet to he done, a solid foundation will be laid on which future workers may build. The main difficulties which confronted th© gco'ogists of the expedition just completed were the climatic conditions which obtain in that region of fog and wind and rain. Several days’ work was lost owing to the difficulty of getting over unknown ground. When the whole landscape was enveloped in the mist the danger of getting lost had continually to be considered. Travelling through bog and fccrub and low bush was painful and clow, and had not for geologists tho compensations which it gave to botanists, in that they were making a close acquaintance with a formula which belonged peculiarly to themselves. It might be a fruitful ‘field for investigation for the botanist mil the zoologist, but an abomination to one who wished to examine thoroughly the underlying rocks. in© whaleboat was of the greatest assistance to the Auckland Island party, as it enabled them to visit widely separated points on tho coast-line of the southern uortion of the large island. The thick covering of peat was a hindrance to the work of the geologist. This is a characteristic "rock” of the island, using that term in its widest sense, which includes anything that plays a part in the solid structure of the earth, a definition which would include ice among the earth s important minerals. This covering or peat is one of tho geological features ot the island. I might say that it is perhaps the onlv mineral oi economic value that we found there. It passes in its lower parts into lignite, and. considering the immense quantities that occur, especially on Campbell Islands, its value is by no means negligable. Although -his covering prevents the solid rock underneath from being examined, it exerts a protective inllucnce on its surface. The nard volcanic rock is so closely covered that the weathering action of rain and frost is practically absent. Except on sea shore and mountain top, where conditions prevent the accumulation ot this product of vegetable life, the coating must be in some places fully forty feet thick Numerous cases observed whore it was twenty and even thirty feet in thickness. This was the greatest difficultv that beset th© geologists in their investigation, 1 but besides this must be reckoned the great one of absolutely unknown land that had to be covered before a detailed examination could be made of anv portion 6f it. Had more time been available a Holier harvest of results would have been reaped than even those of which th© geological section has up to the present been successful iu securing. The delight of being tho first to explore nn unknown and neglected land is a feeling which is impossible to describe, and which is more and more rarely felt, as •even the dark portions of the earth are now being forced to reveal their secrets. THE SUB ANTARCTIC CONTINENT. In my former paper I pointed out that onr Southern islands were part of a continental area extending round Now Zealand, and suggested that of the problems awaiting (olution an investigation 'into the former conditions of this continent was of the highest importance, on .account of its bearing in the distribution of plants and animals throughout the ’whole of those islands, which may be grouped together and called subAntarctic. These include not only our own Southern Island, but all those round i .the South Polar regions, such as Kerguelen Land, the Crozets, Heard Island, the South Shetlands, Tierra del Puego, and other isolated groups between latitude frOdeg south and 70deg. south. One result of the expedition is to determine definitely that the Southern Island of our Dominion formed part of a continental area which extended south of the present mainland of New Zealand. When it first appeared above tho sea it is impossible to say at present. The groups visited, viz., the Snares, the Campbell Islands and the Auckland Islands, contain masses of granite-like rocks, which were heavily eroded at some remote geological date, before other beds were laid down on them.

In the Campbell Islands these consist of sandstones, with seams of poor shaly coal, indicating nearness to land ana shallow water conditions, and over them lie beds of limestone, which closely resemble those at Clarendon in Otago, and those at Amuri Bluff and near Kaikoura. The presence of certain well-known fossilshells and of frequent lumps of flint, show that they are probably of the same geological age and formed under similar circumstances as one of the most widely distributed of New Zealand limestone formations. This points to a common history for these two widely separated localities. The next period in the history of Campbell Island was one of great volcanic activity. Beginning beneath the sea, as so many great volcanoes have doll©., a number of sills were built up, which now form important physical features of this island. Mount Honey (1800 feet) is the highest point, and there are six other summits over 1000 feet in height. No craters now exist, but their former presence is 'proved by the character of the volcanic material which has been ejected. This consists of ashes and scoria, which were the products of spasmodic explosive eruptions, sometimes submarine and sometimes subaerial, true lava flows, which issued from the volcano as a flood of molten, or semi-molten, rock, both of these being associated with a most wonderfully interlacing network of dykes, which have been formed by the consolidation cf molten rock, and forced up fissures in the neighbourhood of the volcano by those tremendous forces, of whose power we can have no adequate conception. This island will be thoroughly described later by Dr Marshall, who, 'assisted by Mr R. Browne, made a complete reconnaissance under great difficulties. He was also able to map thoroughly the foreshore of Perseverance harbour, the principal inlet of tho island. His account differs considerably from that by Dr Filbal, who accompanied the French expedition to observe the transit of Venus in 1874-. The former points out that there are no granites, and no schists, as mentioned by the French geologists, and from his description it seems quite possible that the , party could not have visited some of the spots they described definitely. A special feature of tho geological structure of the island is the existence of two great faults, which have profoundly affected its structure, and also caused the rooks in tho neighbourhood to simulate the structure of slates and schists, which the French scientists mistook for the real tiring. AUCKLAND ISLANDS. The work at the Auckland Islands was carried out by the author of this article, assisted most ably by Mr A. M. Finloyson, M.Sc., of Dunedin. Mr G. S. Collyus, of Canterbury College, also helped the party very materially by tho ready and cheerful way in which 1 he made tracks through difficult country, and assisted in the transportation of tho numerous specimens collected to the flying camps, which were established in different parts of tho island. Without his help many valuable finds would have had to be dropped by the way or left for some investigation. The

country was examined as fully as time and circumstances permitted, and no turraouniab]© difficulties were allowed to stand in the way of visits to likely spots. It was found that the oldest rocks at the Auckland Islands proper are true granites, with beautiful large pink crystals of felsgor, and also n granite-liko rock closely connected I chemically with volcanic basalts. These were followed by vast outpourings of volcanic rocks, chiefly basalts, from several centres of activity, but in tho lowest beds of volcanic material were found abundant fragments of granite gneiss and altered sedimentary rocks, whose existence undoubtedly proves the close proximity of a continental area. In his visit to Disappointment Island Dr Marshall discovered old sedimentary rocks and a series of dykes, which differ considerably from those of the mam island. This discovery is a most interesting one, and its importance cannot be fully appreciated until the evidence has been more thoroughly considered. The Auckland Islands proper are fully twenty-five miles long and fifteen miles wide in the widest part, i.e., at their southern end. Owing to the difficulties mentioned previously, it, was found possible to examine only the southern two-thirds of the group, which consists of Carnley harbour and its neighbouring coasts. An attempt was mad© to cross the northern end of this island, but it was frustrated by. bad weather. Carnley harbour is a magnincent harbour, one of the finest in the world. From ©very point of pewit bears a striking resemblance to that of Akaroa. It is also the enlarged crater of a great volcano. It extends lor nearly fifteen miles from its eastern entrance to the narrow passage winch connects it with the ocean on the west. There are besides two largo arms going north-west, each a fair-sized harbour in itself. They are divided by two peninsulas, which arc exact counterparts of the historical Onawe peninsula in Akaroa harbour. The snlas are largely formed of gronite-like rocks, but the lulls surrounding the harbour are built up of layei after layer of volcanic material, JaTa > and scoria beds till they reach a height of about two thousand feet. The rocks are nearly all of black basalt, and are distinguished by the remarkable fluidity like those poured out from many * Pacific volcanoes. The consequence is that the flows are frequently very thin, and show very-slight difference in level. As they are traced .ior long distances their level character gives a special feature to the landscape, limy rise from the harbour in a senes of steps, to be crowned at the summit by a flat basaltic cap, which is usually the remnant of a large level flow. Some ot those flat-topped hills are several square miles in area, and are only a few square yards, and their * or J a - ?1 a ®" counts for such place names as *l & t; topped Hill” and the "Giants Tomb being applied to the highest elevation. Precipitous faces, unscalable for long distances, showing well marked, basaltic columns are extremely common, and •recall such well-known coses as the Giant's Causeway of North Ireland, F ingall's Cave at Staffa, the palisades of the Hudson river, not to mention numerous instances that could be cited from different parts of New Zealand. Judging from the marked effects of atmospheric and marine denudation the date of this giant volcano cannot be at all recent, and probably corresponds in ego with the ySunger pffrts of Banke Peninsula. No rocks have been found of a later date than the basalts, and no sedimentary -limestones or coal measures h v© been found, although they were diligently searched for, in the hope that some date could be assigned to the period of volcanic action. THE MAGNIFICENT WESTERN CitiFFS. It is possible that the land stood at a h'gher level during the time of its great activity, as valleys have been cut uc-piy in iis slopes, and have thus modified profoundly tho original shape of the volcanic mountain, but it is the extent of marine erosion that is truly remarkable, and shown, in all islands of this region. Their western coasts are always precipitous. At The Snares the granite cliffs rise to a height of 600 ft, The same is true of Campbell Island cliffs, while the western coast of 'the Aucldands is so imposing that muchtravelled members of the expedition, some of whom are familiar with such iron coasts as those of Cornwall, say that they have never seen the like. For twenty miles the cliffs are not less than 40ffft in height, frequently over lOWft, and rising at times perpendicularly for 1300 ft. In only one place on all the western coast is ascent from the sea level possible, and sealers who visited it in pursuit of the fur seal had to be lowered down by ropes to the reefs and piles of debris that fringe its foot in a few places. Little chance of escape have the crew of any ship that strikes tho submerged ledges which divide with narrow width the deqp sea from the precipitous walls. Many a vessel posted as missing must have struck here, been quickly battered into fragments or slipped off into deep water, and not a solitary survivor left to tell the tale of disaster. This line of cliffs gives a magnificent section. From north to south through the island the edges of tho lava flows are seen olearly in wonderful order. On one cliff 1000 feet in height, twenty-nme distinct outpourings were seen with their intermediate beds of scoria and ashes. In another of 1300 feet, forty-two wore counted. The inner structure of the volcanoes are thus exposed. tio much has the sea cut back the western coast that the whole of the present drainage is oashvard up to the edge of the cliffs. Even the puny waterfalls which attempt to cross the western line have their spray blown skyward and eastwaru by tho powerful and continuous westerly winds. Miles of the western fringe ot this land hove been removed since the period of volcanic activity. THE EASTERN COAST LINE. Tho eastern coast line is markedly different. It is a perfect paradise ot secure and commodious harbours, formed by valleys cut out at the time when the land was higher, and now submerged in their lower portion. Carnley Harbour, Port Ross, Norman's Inlet are all harbours which vfoukl be of the greatest use were the land in tneir neighbourhood of any commercial value. Numerous other minor inlets could be mentioned, but the insatiable sea has attacked even those from their western end. Tb© dividing wall between Carnloy Harbour and the western sea has been cut down, and now fierce tides ebb mid flow through tho narrow passage. At the north arm of Carnley the seas are separated by a bare mile of land. A;t the head of Norman Inlet a ridge 1000 feet in height and a chain in width on the top, with precipitous cliffs on either side, is all that remains to prevent the flood of western sea from pouring .through. An observer cannot help but be convinced of the efficiency of sea erosion after a visit to such a coast line, and is disposed to question the wisdom of assigning to it a position of slight importance when compared to the action of rain, frost, ice, and other agents which modify the landscape. In these islands its importance cannot be under-rated, THE GLACIER. PERIOD. ;

The most interesting feature of the geological work of the expedition has been to demonstrate that both the Auckland and Campbell Islands have been subjected to a fairly recent and severe glaciation. Tho evidence is convincing that tho higher parts of the liver valleys were occupied by glaciers. Lateral moraines are extremely common m the vicinity of Carnley Harbour, and Dr Marshall reports their occurrence at Perseverance harbour, in the Campbells. Those probably belong to the last phase of glaciation, whoa the glaciers were merely shrunken remnants. That the glaciation was at ono time more severe is proved by the rounded amphitheatres which head eo many valleys and which can only have been formed by glaciers. There is also much additional evidence, such as the presence of small glacier lakes, bended back by angular debrie.

the occurrence of true hanging vallcvs, of waterfalls coining down from the sides of lateral valleys, of lateral streams flowing over solid rock in no well-defined channel. Norman's Inlet, Cascade Inlet, and Smith’s Inlet are typical valleys, and resemble the West Coast Sounds of the South Island in almost every detail, except that they are on a muck smaller scale. Perseverance harbour, in Campbell Island, is a river valley which has been modified by glacici erosion before it was depressed below tea level. In order to account, for this glaciation it is necessary that the land should have been higher, probably by several thousand feet. This would cause the islands to bo more closely connected witli New Zealand, would allow of a larger space for those plants to grow which have found a last home on the grass-cov-ered and boggy upper slopes. It would explain why the plants and animals are so closely connected with those of New Zealand/ and go a long way to solve many other biological problems. I think I have shown that a good deal of fresh material has been secured by the geologists of the expedition, and the importance of their work cannot yet be fully estimated. When all notoe have been accurately correlated and the microscope has been requisitioned to explain the peculiarities of the extensive petrological collections that have been secured, results null be obtained of which the expedition will by no means be ashamed. There is only one thing wo have not found, i.e., gold or any other metal or mineral of present economic value, nor have we any hope that such exists. Dr Marshall found crystals of tho semiprecious stone called ziscon in tho Campbell Islands, and the Auckland Island party came across a few bands of coal between the lava flows, evidently formed from a thick coating of peat, which must have covered the hills when the volcanoes were in full activity, just as they .are covered now when they are dormant, and; never likely to wake from their long sloop.