IN TOUCH WITH NATURE

Otago Witness, Issue 3757, 16 March 1926, Page 55

IN TOUCH WITH NATURE

HISTORY IX THE ROCKS. By J. DRUMMONI PUS., PK f\ A Palmerston North resident who spent his summer holidays at Lake Manapouri has asked for information as to the geological history of that wild and fascinating district. The request should have been made to Professor J. Park, of Dunedin. He has done field work there particularly in the Waiau Valley, but evo he would have some difficulty in summarising in a few paragraphs the district’s geological features. One of the features is a vast land surface reduced by erosion to the condition of a plain, but not quite a plain. In geological literature, this formation is known as a peneplain—“almost a plain”—and in the geological history of New Zealand that particular peneplain is given the title of the Fiordland Peneplain. When it was formed it was merely a continuation of an Otago peneplain, of which Old Man, Rock and Pillar, and the Lammerlaws are some of the remnants. The Otago peneplain extended far beyond the provincial boundaries fixed by human beings, reaching as far north a* Kurow. Early in the Miocene Period of the Tertiary Era the Otago peneplain was slowly submerged by the sea. Vegetation grew and decayed on the banks that were formed, and the sediments were mixed with seams of decomposing peaty material, which later were continued to subside in the Middle and the Upper Miocene Period. Early in the Pliocene Period, which followed the Miocene Period, and closed the Tertiary Era, there was a rapid uplift; but the ancient peneplain was not uplifted uniformly; in some places it was in the form of roughly cube-shaped blocks, in other places it was tilted into sloping blocks.

The origin of the trough-like valley through which the Waiau, one of the great rivers of New Zealand, flows, has been the subject of speculation gy geologists for many years. The general opinion seems to be that it was a gigantic fault, a dislocatjoT in the rocks produced by the walls of a fissure moving. The trough includes the basins of Lake Manapouri and of Lake Te Anau. It is conjectured that the great arms of those lakes—Hope Arm and South Arm in Lake Manapouri and North Fiord, Middle Fiord, and South Fiord in Lake Te Anau —follow the course of faults that run at right angles from the big fault. Some writers believe tha* the lakes’ arms and canons were excavated by immense glaciers that flowed over that region in Pleistocene times. That period was noted for glacial expansion unparalleled in the world’s history. it saw the end of the Tertiary Era and the dawn of the Quarternay Era, which is man’s era. It is called Pleistocene—“most recent”—because most species of shellfish whose remains are found in it are still living. But Professor Park has found no evidence that the arms and canons were excavated by Pleistocene glaciers; he favours the theory that they originated in faults. The story dimly written in the rocks of the Waiau Valley and near Manapouri and Te Anau is a story of faults and crumplings, rifts, rockrents, and foldings, depressions, and uplifts.

The work of the ancient glaciers is evidenced by Professor Park’s description of rounded and flowing contours of the mountains, by U-shaped valleys, by hanging valleys, always scooped out by glaciers, by mountain tarns, and by roclibasins. The ice-sheet seems to have moved down to the coast, now indented by the famous sounds, and discharged on the floor of the sea the loads of rocks it picked up. All the West Coast Sounds are shallower at the entrance than inside. Professor Park explains the shoaling by the glaciers accumulating their moraines under the sea before they finally retreated. After their retreat, there were formed several remarkable rents or chasms that now traverse land covered with grass. The largest is more than 50ft deep at the top, it is from a few yards wide to 10 yards wide. Their origin is obscure, but Professor Park suggests that they may be rents made by earthquakes, or gashes caused by the sagging or creeping of precipitous mountain walls near a profound canon in the Greenstone Valley. The largest and most impressive stretch of rocks grooved by glaciers in New Zealand is on the south-west shore of Ci 1 Cove, at the south end of Lake Manapouri. It was discovered in 1919 by Mr J. M. Fouler, of Invercargill, and Mr Guy Morrell, of Manapouri.

A small, snow-white moth, singularly beautiful in its purity, lias been sent hy Mr T. Bettjeman, Mangapurua Valley. Wanganui River. He states that he lias not seen the species in any other part of New Zealand, and has seen it only about six times during the eight years he has lived at Mangapurua Valley. lie adds that members of the species, like many other moths, nre nocturnal, and are attracted by the light. Mr G. V. Hudson, of Karori, Wellington, has kindly inJentiiled the beauty, ns New Zealand's whit** plume moth, Alucita monospilalis. He will describe it and give its life history, with figures of its caterpillar and chrysalis, in a new edition of his “New Zealand Moths nnd Butterflies,” which will he published soon. He reports that the white plume moth is fairly common in forest districts; about six individuals may be seen in a season.

Birds in New Zealand forests may be attracted to within a few feet of an observer by several devices. Maoris use a thin, long lenf placed between the lips, by which they produce a piercing sound, in imitation of a bird’s excited alarm notes. Birds from far nnd near, thinking apparently that one of their company is in trouble, come down on the lower branches and give unmistakable signs of distress An*enrly New Zealand ornithologist, when he went into the forests, carried in his pocket an old-style matchbox and a nail. By scratching the nail on the matchbox, he male a rasping noise, to which small birds never failed to respond. Another device is to place the lips on the back of the hand, draw iu the breath, and make a

shrill sibilant noise. When this is done forests that were still and silent become alive with birds. A most elaborate device, used by Captain O. Schulz*, of Auckland, when he was a 'in the Old Country, to imitate the nightingale, inay be successful in imitating some New Zealand birls. lie found a finely developed goose quill, cut it at the pointed end and at the pithy end, and made a tuhe, as long and ns nearly perfect as possible. He converted it into a whistle on the pattern of an ordinary penny whistle, with a plug that fitted perfectly, and a sharp and -decided cut into the quill below the plug. Inserting the little whistle about three-quarters of an inch into a tumbler of water, he blew into it and imitated even the most exquisite notes of the world’s greatest songster. Going down to the river ovpry morning for a swim, Mr G. J. MacCormae, Fernhill, Hawke’s Bay, has been interested in the actions of birds that visit a shallow pool. Ilis description seems to show that they nre black-fronted terns, known to Maoris as tara. They circle about him, uttering shrill notes, nnd then return to the pool. He often hears the notes at night, as the birds fly high overhead. The black-* fronted tern, for some reason not appar*i ent, is becoming rare. This is doubly regrettable, ns, added to its grace and beauty, is its usefulness. It feeds largely on the grubs of insects and on small lizards. Large flocks of these terns sometimes rest motionless on the ground with their wings extended, and maintain that singular position for some time. They lay their eggs on the bare ground, without making an attempt at a nest. They ara clamorous at the breeding season. If an intruder approaches he is assailed with swift dartings, accompanied by noisy, harsh and grating cries. Every evening hundreds of seagulls make their way up the river. Mr MacCormae has heard the sparrowhawk at his place, and occasionally he hears the morepork owl. During his three years’ residence at Fernhill he has seen “that lovable little chap,” the tomtit, only once. The bell-* bird’s notes are seldom heard, Me MacCormae often hears “that shy cue-: tomer,” the grey warbler, which he knew; in his boyhood as Jenny Wren. Black•* birds, song thrushes, mynahs, and rooks are very plentiful. In the last week in January, Mr MacCormae heard a chaffinch, the first he had heard for many years.