In Touch With Nature

Hawke's Bay Tribune, Volume XVI, Issue 209, 21 August 1926, Page 9

In Touch With Nature

<By

J. DRUMMOND, F.L.S., F.Z.S.)

Nature notes will appear in the “Tribune” every Saturday. Mr. Drummond wil be pleased to receive from our readers, notes relating to any remarkable incident or peculiarity they have noticed in bird, animal, or plant life, and he will also be pleased to answer questions. Letters should be addressed to him personally, care of Tribune Office, Hastings. ® ® ® ® WRITTEN IN THE ROOKS. TPROM the horizontal, or almost ■w horizontal form in which sedimentary rocks originate, they may be altered until they tilt at all angles. Some of them now stand up on end. Others have been completely overturned. The folding that produces this is the result of long and stupendous pressure. Rocks yield to pressure without breaking, in the same way as cloth may be folded. The folds in rocks sometimes are so small that several could be included in a . piece no larger than a man’s hand; sometimes they change the face of a whole district. Rocks often fold into the form of arches; others fold into troughs. These natural arches are anticlines, and troughs synclines. Rocks in an upland which has Kawhia and Raglan as its chief centres of population and along which the principal road between Auckland and Taranaki ran before the Main Trunk Railway was opened, are arranged in a gigantic trough twenty miles wide. It is complete only south of the Kawhia depression ; northward its great western wing was depressed below sea-level in Tertiary times when Nature traced some of New Zealands present features. The trough is traversed by many faults. These have broken the rocks into large blocks. The main mass of upland is formed of rocks laid down in the Mesozoic Era, which came after the Palaeozoic, and before the Tertiary or Cainozoic, the era that immediately preceded the one in which we live. ®® ® ®

A DILAPIDATED VOLCANO. The, upland extends along the coast as a distorted plateau, deeply dissected. An ancient dilapidated volcano, Mount Pirongia, rises from it for 3150 feet in the south,, and a mighty corner buttress. Mount Karioi, rises 2420 feet south of Raglan Harbour. In the north-west corner of the district, there is an ancient surface that rises from sea-level near the coast to 1100 feet. Raglan Harbour was formed by the sea invading the lower part of a branching rivervalley. Kawria, Aotea, and Whaingaroa Harbours are the result of an invasion by the sea of valleys eroded by streams. Remnants of tea terraces along the shore show that, although the land there has sunk, to admit the sea, it once wag lower even than it is now. A bench, from 190 feet to 250 feet high, up to foil chains wide, backed by an old seacliff, runs for half a mile along the coast. North of Aotea Harbour there are well-marked terraces about 200 feet high. The flat tops of many high ridges indicate ancient shores. A lowland extending for about thirteen miles from Waikorea Stream to Raglan Harbour, probably originated when the shore was from 500 feet to 600 feet higher than it is now. Most of the hot springs in that part issue from Mesozoic rocks. ®®® ® . LIFE HISTORIES OF LAKES. Every lake, in every country, like has youth, maturity, old age, decay, every individual and every nation, death, and is under one of the ereatest laws of Nature, the struggle for existence. The life-histories of lakes in the basins of the Waikato River, which drains the eastern side of the upland, are not less interesting than the life-history of the ristorical river itself. Lakes in the middle basin of the Waikato have died since settlement began. The bed of Lake Rotorangi, six miles south-south-east of Cambridge, is now dry land. The bed of Round Lake, two miles south-.

Ohaupo. is dry except after rain. The area of Lake Hamilton has been reduced by the draining of swamps to the west. The Waikato, carrying sand and silt, has dammed the " gawara River, until it s lower course for three miles, is a narrow winding lake. Right lakes in the lower basin of the Waikato, and east of the river, have several characters in common. All are very shallow; their surfaces are slightly above the normal river level of the river, their outlets are across wide swampy flats of the present flood plain: their flood-plains pass gently below the surfaces of the water. Encroaching sand-dunes, blocking small streams? have formed ponds near Raglan, North Head and north of Kawhia. Parangi, a pond near Kawhia, 150 fete above sea-level, lies amongst old fixed sand-dunes, cemented with iron oxjde, but loose sand is rapidly encroaching on it. Many ponds and lakes in the middle basin of the Waikato probably are remnants of lakes that once were much tore extensive. The lakes of the Wai ka'o, one of the most noticeable randscipe features of that part, seem to be pirticularlv ephemeral—this word miv be used with strict propriety wt».'i thousand years are as a d .’. —and they may be merely a n incid ,ut in the district’s geological liistorv. Wi ll ponds/ swamps, lakes ajj rivers, all changing and all passing their cycles, that part of New Zealand is an open book in which he who rung may read chapters in the Dominion’s history. ®® ® ® LOWER WAIKATO BASIN. During early Tertiary times, the site of the Lower Waikato basin was lowland, probably the wide lower valley of a river. A slight depression of the land allowed swamps to extend over the lowland. The swamp was fflogt luxuriant ju

the hollows of the old land. Layers of silt and mud were spread over the swamps. These deposits were aooa covered by vegetation in their turn. Then sediment in large quantities was deposited on the great swamp. Vegetation overgrew it also; and that vegetation forms the upper coal-seam at Huntly and Rotowaro. Depression continuing, the swamp was covered by the siltg and muds that now form grey and brownish claystones which over-lie the coal. The Gl»n Massey coal is believed to have beep formed in the same wide valley in which the Huntly coals accumulated, but it wa 8 at a later period, when the depression of the land was morn advanced, and after the sea had penetrated further inland, and the Huntly coals had been al] covered with mud. Between South Head and Kawhia and Te Mairi, in layers of sandstone,. petrified trunks and stumps of trees stand where they grew.

® ® ® AMMONITES BELEMNIJES. The sable g eas of the Mesqyoic a were characterised by a great development of molluscan life. Their chambered division wa s represented by ammonites, and the cuttlefishes by beleinnites. Both these molluscs, now extinct, have left their remains in many parts of the world, to help in reading the history of their times. Both ammonites and belemnites are scattered over the Huntly-Kawhia district, with the sheila of other Mesozoic magnates that were their contemporaries. All thia and more also, is set out by Dr. J. Henderson and JjlL. I. Grange in Bulletin No. 28 of the New Zealand Geological Survey, recently issued from the Government Printing Office. This is the latest of an admirable series of geological works published by the Survey. An examination of the coal-beds near Huntly was the basii of the bulletin. The authors extended their researches to a comprehensive geological survey. The district contains no precious metals, but it is rich in brown coal, limestone and clays; and its geological history, as sketched in this bulletin, is more fascinating than any human history. In comparison with the geology of that district, with itg ups and downs, the migrations of creatures that peopled it long ago, the advance and retreat of the sea, and outbursts pf volcanic activity, the strife of powers and principalities sinks into the limb' of insignificance. ® ® ® ® OUR COMPLICATED GEOLOGY. In spite of skilful and able work by New Zealand geologists, this Dominion's long and complicated geological history has not been clearjy read. The land has often risen and subsided. Some of these movements have affected the land and the neighbouring ocean floor as a whole; others have had only a lueal ettecr. he outline has altered during the ages. At one period New Zealand was'a continent. At another period it almost or completely disappeared into the ocean. Great changes have been made on the surface of the land. Mountain chains have been planed down by Nature’s gigantic tools, and new mountains have been built up, step by step, in their place. The changes have been slow but incessant and exceeding sure. New Zealand received her frame in the Palaeozoic Era, the era of Early Life, and in the past she never was the same as she is now. ■’, ® ® ® ® '< “GONDW ANA-LAND.” When the world was very young New Zealand it is believed, was tbe dreary foreland of a land-mass which extended far west, and which may have been a continent that was dismembered. This lost continent. i« known to geologists a.- n-ond«»na-land. A great Mesozun . weed, abundant in Mesozoic rocks throughout the Southern Hemisphere, a weed that seems, like the bracken fern in these times, to have flourished vigorously in many widely separated areas, left is remains in New Zealands Mesozoic rocks. A cosmopolitan fern known as the great Carboniferous weed apparently has not been found in any part of New Zealand. A petrified Jurassic forest at Curio Bay, Waikawa, on the southern coast of the. South Island is one of the most interesting collections of Mesozoic fossil plants known. Investigation of the geological succession of sedimentary rocks in New Zealand is difficult, but the geological structure here is devoid of some complexities that distinguish the continental areas of the Northern Hemisphere. As Mr P. G. Morgan, director of the Geological Survey, states, New Zealand geologists have a rich field of research, but patient workers in the field must wrestle with big problems.