THE NEW ZEALAND OFFICIAL YEAR-BOOK, 1932

THE Dominion of New Zealand consists of two large and several small islands in the South Pacific. These may be classified as follows:—

(a) Islands forming the Dominion proper, for statistical and general practical purposes:—

In all further references in this volume, unless the context indicates the contrary, Chatham Islands and Stewart Island are classed with the South Island.

(b) Outlying islands (total area, 307 square miles) included within the geographical boundaries of New Zealand as proclaimed in 1847:—

(c) Islands (total area, 293 square miles) annexed to New Zealand:—

The total area of the above is 104,015 square miles. Elsewhere in this issue the aggregate area appears as 66,390,262 acres—i.e., 103,735 square miles. This covers not only the Dominion proper, but also the outlying islands and the Kermadecs.

The Proclamation of British sovereignty over New Zealand, dated the 30th January, 1840, gave as the boundaries of what was then the colony the following degrees of latitude and longitude: On the north, 34° 30' S. lat.; on the south, 47° 10' S. lat.; on the east, 179° 0' E. long.; on the west, 166° 5' E. long. These limits excluded small portions of the extreme north of the North Island and of the extreme south of Stewart Island.

In April, 1842, by Letters Patent, and again by the Imperial Act 26 and 27 Vict., c. 23 (1863), the boundaries were altered so as to extend from 33° to 53° of south latitude and from 162° of east longitude to 173° of west longitude. By Proclamation bearing date the 21st July, 1887, the Kermadec Islands, lying between the 29th and 32nd degrees of south latitude and the 177th and 180th degrees of west longitude, were declared to be annexed to and to become part of the then Colony of New Zealand.

By Proclamation of the 10th June, 1901, the Cook Group of islands, and all the other islands and territories situate within the boundary-lines mentioned in the following schedule, were included as from the 11th June, 1901:—

A line commencing at a point at the intersection of the 23rd degree of south latitude and the 156th degree of longitude west of Greenwich, and proceeding due north to the point of intersection of the 8th degree of south latitude and the 156th degree of longitude west of Greenwich; thence due west to the point of intersection of the 8th degree of south latitude and the 167th degree of longitude west of Greenwich; thence due south to the point of intersection of the 17th degree of south latitude and the 167th degree of longitude west of Greenwich; thence due west to the point of intersection of the 17th degree of south latitude and the 170th degree of longitude west of Greenwich; thence due south to the point of intersection of the 23rd degree of south latitude and the 170th degree of longitude west of Greenwich; and thence due east to the point of intersection of the 23rd degree of south latitude and the 156th degree of longitude west of Greenwich.

By mandate of the League of Nations the New Zealand Government also now administers the former German possession of Western Samoa; and, jointly with the Imperial Government and the Government of Australia, holds the League's mandate over the Island of Nauru.

By Imperial Order in Council of the 30th July, 1923, the coasts of the Ross Sea, with the adjacent islands and territories, were declared a British settlement within the meaning of the British Settlements Act, 1887, and named the Ross Dependency. The Governor - General of New Zealand is Governor of the Ross Dependency, and is vested with the administration of the dependency.

By Imperial Orders in Council of the 4th November, 1925, the Union or Tokelau Islands (consisting of the islands of Fakaofu, Nukunono, and Atafu, and the small islands, islets, rocks, and reefs depending on them) were excluded from the Gilbert and Ellice Islands Colony, and placed under the administration of the Governor-General of New Zealand. In accordance with a provision of the second of these Orders in Council, the Governor-General's authority and power in connection with the administration of the islands were, by New Zealand Order in Council of the 8th March, 1926, delegated to the Administrator of Western Samoa.

The mountainous character of New Zealand is one of its most striking physical characteristics. In the North Island mountains occupy approximately one-tenth of the surface; but, with the exception of the four volcanic peaks of Egmont (8,260 ft.), Ruapehu (9,175 ft.), Ngauruhoe (7,515 ft.), and Tongariro (6,458 ft.), they do not exceed an altitude of 6,000 ft. Of these four volcanoes only the first-named can be classed as extinct. Other dormant volcanoes include Mount Tarawera and White Island, both of which have, in recent years, erupted with disastrous consequences. Closely connected with the volcanic system are the multitudinous hot springs and geysers.

The South Island contains much more mountainous country than is to be found in the North. Along almost its entire length runs the mighty chain known as the Southern Alps, rising to its culmination in Mount Cook (12,349 ft.). No fewer than seventeen peaks of the Southern Alps attain a height of over 10,000 ft. Owing to the snow-line being low in New Zealand, many large and beautiful glaciers exist. The Tasman Glacier (Southern Alps), which has a total length of over eighteen miles and an average width of one mile and a quarter, is the largest. On the west coast the terminal faces of the Franz Josef and Fox Glaciers are but a few hundred feet above sea-level.

The following list has been compiled from various sources, and does not purport to be free of omissions, nor is exactitude claimed in respect of the elevations shown, many of which are known to be only approximate.

The 1931 issue of the Year-book contained a list, not claimed as exhaustive, of 223 named peaks of 7,500 ft or more in altitude. In this issue, the list of South Island mountains is restricted to a minimum of 9,000 ft. altitude.

The hot springs of the North Island form one of the most remarkable features of New Zealand. They are found over a large area, extending from Tongariro, south of Lake Taupo, to Ohaeawai, in the extreme north—a distance of some three hundred miles; but the principal seat of hydrothermal action appears to be in the neighbourhood of Lake Rotorua, about forty miles north-north-east from Lake Taupo. By the destruction of the famed Pink and White Terraces at Lake Rotomahana during the eruption of Mount Tarawera on the 10th June, 1886, the neighbourhood was deprived of attractions unique in character and of unrivalled beauty; but the natural features of the country — the numerous lakes, geysers, and hot springs, some of which possess remarkable curative properties in certain complaints—are still very attractive to tourists and invalids. The importance of conserving this region as a sanatorium for all time has been recognized by the Government, and it is dedicated by Act of Parliament to that purpose.

There are also several small hot springs in the South Island, the best known being those at Hanmer.

The following article on the mineral waters and spas of New Zealand is by the Government Balneologist, Dr. J. D. C. Duncan, M.B., Ch.B. (Edin.), Member of the International Society of Medical Hydrology, Fellow of the Royal Society of Medicine, and Fellow of the Royal Geographical Society:—

The following account of the rivers of New Zealand is by Professor R. Speight, M.Sc., F.G.S., Curator of the Canterbury Museum. The approximate length of course which has been added in parentheses following the name of the river has been supplied by the Department of Lands and Survey.

In a country like New Zealand, with marked variations in topographic relief and with a plentiful and well-distributed rainfall, the rivers must necessarily form characteristic features of the landscape. Mountains, however, exert an important influence on their adaptability to the necessities of commerce, reducing their value on the one hand while increasing it on the other. Owing to the steep grades of their channels few of the rivers are fitted for navigation except near their mouths, but to compensate for this disability they furnish in many places ideal sites for power plants. No country south of the Equator, except Chile and Patagonia, possesses such stores of energy conveniently placed, which cannot become exhausted until the sun fails to raise vapour from the neighbouring seas—a contingency to be realized only when life on the earth is becoming extinct.

The only part of the country which possesses rivers capable of being used for navigation is the North Island. The relief is not so marked as in the South, and many streams flow in deep beds, with somewhat sluggish current. There are flowing into the Tasman Sea rivers like the Waikato (220), Wairoa, Mokau, and Wanganui, which served the Maoris as important means of communication, and which are decidedly useful for the purposes of modern transport. The first-mentioned of these is by far the most important. Rising in the flows of Ruapehu, and receiving numerous affluents from the western slopes of the Kaimanawa Range, it pursues a northerly course for twenty miles with all the features of a mountain torrent till it enters Lake Taupo. Almost immediately on leaving this it plunges over the Huka Falls, formed by a hard ledge of volcanic rock, and then runs first north-east and then north-west till it reaches the sea, the amount of water discharged exceeding 800,000 cubic feet per minute. In certain parts of its course the valley is gorgelike in character and picturesque rapids obstruct its navigation, but in its lower reaches it widens out and flows for long distances through marshes and shallow lakes, and empties into the sea by a wide estuary, which is unfortunately blocked by a bad bar. It receives on the west a large tributary, the Waipa—itself also navigable for small steamers, and a river which may ultimately play no small part in the development of the south-western portion of the Auckland Province.

The Northern Wairoa (95) shows features which resemble those of the Waikato. It rises in the hilly land of the North Auckland Peninsula, and flows south as a noble stream till it enters Kaipara Harbour, a magnificent sheet of water with many winding and far-reaching arms, but with its utility greatly discounted by the presence of a bar which, though with sufficient depth of water for vessels of moderate size, is frequently impracticable. The total estimated discharge from the streams running into the Kaipara Harbour is about 500,000 cubic feet per minute, of which the Wairoa certainly contributes one-half.

The Mokau River (75), which enters the sea about sixty miles north-east of New Plymouth, is navigable for a considerable distance in its lower reaches. Here it is flanked by limestone bluffs, clad with a wealth of ferns and other native vegetation, forming one of the most picturesque rivers of the country. Higher up, as in the Waikato, there are fine falls, which may ultimately be used for power purposes owing to their proximity to one of the important agricultural districts of the North Island.

The last of the four principal navigable rivers on the west coast is the Wanganui (140). This river gathers its initial supplies from the western flanks of the volcanic ridge of the centre of the Island, from which numerous streams run west over the Waimarino Plain in somewhat open channels till they coalesce and form the main river. Other tributaries, such as the Tangarakau and the Maunganui-te-ao, subsequently add their quota, and the river then flows in a southerly direction in loops and windings depressed far below the level of the coastal plain, between high papa bluffs clad with rich vegetation, till it reaches the sea as a deep tidal stream, the amount of its discharge being estimated at over 500,000 cubic feet per minute. Through the greater part of its course it has a characteristic trench-like channel, with a fairly even gradient, and with only slight interruptions from rapids. At low water these are most troublesome, but at times of high river-level they are passed without serious difficulty. This fine stream affords communication into a country difficult of access by road or railway, and it may be taken as typical of other smaller streams to the west, such as the Waitotara (50), the Patea (65), and the Waitara (65), which are navigable to a less extent, principally owing to the obstructions of timber in their channels; while the rivers lying more to the east and with courses parallel to the Wanganui—e.g., the Rangitikei (115) and the Wangaehu (85)—are more rapid and have little adaptability to the needs of transport. Further east still, in the neighbourhood of the Ruahine Mountains, the rivers become true mountain torrents, with steep grades and rapid currents.

On the other coast of the North Island the only streams capable of being used for navigation except just at their mouths are those running into the Firth of Thames—the Piako (60) and the Waihou (90). But no account of our navigable rivers would be complete without a reference to the "drowned rivers" which characterize the northern parts of the Island. The Kaipara may be taken as a typical case of such, for the harbour merely represents the depressed and sunken lower reaches of the Wairoa and other streams. A further notable case is the Hokianga River (40), which runs for twenty miles between wooded hills and receives numerous tributaries from them, tidal for a considerable part of their courses, and allowing water communication to be used for at least fifteen miles from the point where actual discharge into the open sea takes place.

The remaining rivers of the North Island of any importance rise in the mountain axis that stretches from near Wellington towards the eastern margin of the Bay of Plenty. Towards the southern end, where it lies close to the shore of Cook Strait, the rivers from it are short and swift, the only exception being the Manawatu (100), which has cut a deep gorge in the mountain barrier and drains an extensive basin lying on the eastern flanks of the Ruahine Range to the north, and of the Tararua Range to the south, as well as a considerable area of country on the slopes of the Puketoi Range, its headwaters in this direction reaching nearly to the east coast of the Island. The Manawatu has an estimated discharge of over 600,000 cubic feet per minute, and judging by this it must be considered the second largest river in the North Island. Although the Manawatu is the only stream which has succeeded up to the present in cutting through the range at its head, several of the rivers flowing west have eaten their way far back, and in future ages will no doubt struggle with the Manawatu for the supremacy of that tract of land lying to the east of the range. Remarkable changes are likely to occur in the direction of drainage, especially if the earth-movements now in progress in the neighbourhood of Cook Strait continue for any lengthy period.

The central and southern parts of the Tararua and Rimutaka Ranges are drained by the Ohau, Otaki (30), Waikanae, and other streams flowing into Cook Strait; by the Hutt River (35), which flows into Wellington Harbour; and by the Ruamahanga (70) and its tributaries, flowing through the Wairarapa Plain. These last include within their basins some amount of papa-country as well as steep mountain-slopes. While in the former they run in deep narrow channels, but when free from it they spread at times over wide shingly beds in a manner more characteristic of the streams of the South Island.

Several large rivers rise on the Ruahine Mountains and their northerly extensions. The chief of these flowing into Hawke's Bay are the Ngaururoro (85), Tukituki (65), Mohaka (80), and Wairoa (50), the first being noteworthy for the enormous amount of shingle it has brought down; while farther north the Waipaoa (50) runs into Poverty Bay and the Waiapu (55) into the open sea, both draining an extensive area of rich papa land. From the north-western side of the range the Whakatane (60), and the Rangitaiki (95), two considerable streams, flow into the Bay of Plenty.

The chief factor which determines the characters of the rivers of the South Island is the great mountain mass of the Southern Alps, with its extensions and semi-detached fragments. Its general direction is parallel to the west coast of the Island, and nearer to this coast than to the eastern one; it also lies right athwart the path of the wet westerly winds which prevail in these latitudes. The moisture collected during their passage across the Tasman Sea is precipitated in the form of rain on the coastal plain and the hills behind it, while the mountain-tops intercept it chiefly in the form of snow, the amount of annual rainfall varying from about 100 in. at sea-level up to over 200 in. near the main divide. The eastern slopes of the range receive less rain, and are increasingly drier as the coast is approached, but there the amount is slightly augmented by moist winds coming from the open ocean to the east. In the higher mountain valleys on both sides of the range lie numerous glaciers, either of the small cliff type or large ones of the first order, the most notable being the Tasman, Hooker, Mueller, Godley, Rangitata, Lyell, and Ramsay on the east, and the Franz Josef and Fox on the west. The chief large rivers of the central district of the Island rise from the terminals of the glaciers and issue from the ice as streams of considerable volume. They reach their highest level in spring and summer, for not only does the heavier rainfall of that time of the year serve to swell them inordinately, but the snow and ice are melted under the combined influence of the rain itself and of the strong sun-heat. Although they are almost always more or less turbulent and dangerous to the traveller who attempts to ford them—in the warm months of the year they are liable to sudden and serious floods, and formerly they frequently blocked communication for weeks at a stretch—now, however, many of the worst streams have been bridged, and communication is thus easier and less precarious.

The general form of these valleys is of a fairly uniform type. Their heads are usually amphitheatre - like in shape, and for some distance they are occasionally covered by old moraines, and the course of the stream is impeded by huge angular blocks washed out of these or shed from the steep slopes; at times, too, the rivers flow through deep and somewhat narrow gorges. Lower down the valleys open out, with even steep sides, nearly perpendicular at times, and with flat floors covered by a waste of shingle, over which the rivers wander in braided streams. The sides are clad with dense bush for a height of approximately 2,500 ft., that merges into a tangle of subalpine scrub, to be succeeded after another 1,000 ft. by open alpine meadow, gradually passing upward into bare rock and perpetual snow.

After leaving the mountains the streams flowing to the West Coast cross the narrow fringe of aggraded coastal plain, and cut down their channels through old glacial drifts which furnished in former times rich leads of alluvial gold. The mouths of these rivers are usually blocked by shallow bars, but after heavy floods a channel may be scoured out, only to be closed, when the river falls, by the vast quantities of drift material moved along the beach by the heavy seas and the strong shore currents which sweep the open coast. It is only where it is possible to confine the river-mouths and direct their scour that open channels can be permanently maintained, and even these entrances are at times extremely dangerous to shipping.

The chief rivers which flow from the central portion of the Southern Alps to the Tasman Sea are the Taramakau (45), Hokitika (40), Wanganui (35), Wataroa (35), Waiho, Karangarua (30), Haast (60), and Arawata (45). All rise in glaciers, and their valleys are remarkable for their magnificently diversified bush and mountain scenery. Occasionally lakes, ponded back behind old moraines or lying in rock-bound basins and fringed with primeval forest, lend charm to the landscape, and make a journey along the Westland Plain one of the most delightful in New Zealand from the scenic point of view.

Farther north glaciers are absent, but the heavy rain feeds numerous large streams and rivers, the most noticeable being the Grey (75) and the Buller (105), the latter being in all probability the largest on the west coast, the amount of its discharge being estimated at nearly 1,000,000 cubic feet per minute.

The general features of the rivers which flow into the West Coast Sounds are somewhat similar, except that few rise in glaciers, and there is no fringe of plain to the mountains. The valleys have steeper sides, waterfalls and lakes are more common, and are ideally situated for power installations. One of the large rivers of this area is the Hollyford (50), which flows into Martin's Bay; but the largest of all is the Waiau (115), which drains the eastern side of the Sounds region, receives the waters of Lakes Te Anau, Manapouri, and Monowai, and enters the sea on the south coast of the Island.

The rivers on the eastern slope of the Alps present features similar to those of the west coast in their upper courses, but the valleys are broader and flatter, floored from wall to wall with shingle and frequently containing large lakes of glacial origin. In those cases where lakes do not now exist there are undoubted signs that they occurred formerly, having been emptied by the erosion of the rock-bars across their lower extremities and filled at the same time by detrital matter poured in at their heads.

The largest of all these rivers is the Clutha (210); in fact, it discharges the greatest volume of water of any river in New Zealand, the amount being estimated at over 2,000,000 cubic feet per minute. The main streams which give rise to this river flow into Lakes Wanaka and Hawea, and have their sources in the main divide to the north of the ice-clad peak of Mount Aspiring and in the neighbourhood of the Haast Pass. After flowing as a united stream for nearly thirty miles it receives from the west a tributary nearly as large as itself called the Kawarau, whose discharge has been accurately gauged by Professor Park at 800,000 cubic feet per minute. This great volume of water is due to the fact that the Kawarau drains Lake Wakatipu, which serves as a vast reservoir for the drainage of a considerable area of mountain country, including snow-clad peaks at the head of the lake. The united streams continue in a south-easterly direction, and their volume is substantially increased by the Manuherikia on the east bank as well as by the Pomahaka on the west. The course of the Clutha lies through the somewhat arid schist region of Central Otago, gorge alternating with open valley and river-flats; but some ten miles or so before it reaches the sea it divides, only to reunite lower down and thus include the island known as Inch-Clutha. It almost immediately afterwards enters the sea, but its outlet is of little use as a harbour owing to a shifting and dangerous bar. Portions of its course are navigable to a very limited extent, but it is more important commercially, since it has yielded by means of dredging operations great quantities of gold; in fact, it may be regarded as a huge natural sluice-box, in which the gold disseminated through the schists of Central Otago has been concentrated through geological ages into highly payable alluvial leads.

The following large rivers belong to the Southland and Otago District, but do not reach back to the main divide—the Jacobs (65), Oreti (105), Mataura (120), and Taieri (125); and forming the northern boundary of the Otago Provincial District is the Waitaki (135), which drains a great area of alpine country, and includes in its basin Lakes Tekapo, Pukaki, and Ohau. Its main affluents are the Tasman and the Godley, rising in glaciers of the same names near the axis of the range where it is at its highest. As the river approaches the sea it crosses shingle plains, through which it has cut a deep channel flanked by terraces, which rise bench-like for some hundreds of feet above the present level of the river. Its general features are similar to those of the rivers of Canterbury farther north, except that a larger proportion of the course of the latter lies across the plains and uninterfered-with in any way by the underlying harder and more consolidated rocks. The four principal rivers which rise in glaciers are the Rangitata (75), Ashburton (67), Rakaia (95), and Waimakariri (93); while farther north are the Hurunui (90), and Waiau (110), snow- and rain-fed rivers rising in the main range beyond the northerly limit of glaciers; and there are other streams—such as the Waihao (45), Pareora (35), Opihi (50), Selwyn (55), Ashley (55), and Waipara (40) —which do not reach beyond the outer flanking ranges, and are almost entirely rain-supplied.

According to recent investigations the low-water discharge of the Waimakariri is approximately 80,000 cubic feet per minute, but it frequently rises in normal flood to 500,000 cubic feet per minute.

The rivers flowing to the east all carry down enormous quantities of shingle, but in former times they carried down even more, and built up the wide expanse of the Canterbury Plains by the coalescing and overlapping of their fans of detritus, the depth of shingle certainly exceeding 1,000 ft. Subsequently, when conditions, climatic or otherwise, slightly altered, they cut down deep through this incoherent mass of material, forming high and continuous terraces. Nowhere is the terrace system more completely developed than at the point where the rivers enter on the plains, for there the solid rock that underlies the gravels is exposed, and by the protection that it affords to the bases of old river flood-plains or former terraces it contributes materially to their preservation in a comparatively uninjured condition. The valleys of all these rivers are now almost treeless except in their higher parts, but there the mixed bush of Westland is replaced by the sombre beech forest; it is only in exceptional cases that the totara, which forms an important element of the bush on the hills to the west, crosses the range and covers portions of the sides of the valleys on the east.

Both the Hurunui and the Waiau have cut down gorges through semi-detached mountain masses of older Mesozoic rock, a result probably accelerated by the movements of the earth's crust; and farther north, in Marlborough, the Clarence (125), Awatere (70), and Wairau (105) have their directions almost entirely determined by a system of huge parallel earth-fractures, running north-east and south-west, and the rivers are walled in on either side by steep mountains for the greater part of their length. The Clarence Valley is the most gorge-like, since it lies between the great ridges known as the Seaward and Inland Kaikouras, which reach a height of about 9,000 ft. The last river of the three, the Wairau, flows for a considerable distance through a rich alluvial plain, and enters Cloudy Bay by an estuary which is practicable for small steamers as far as the Town of Blenheim. The most important of the streams on the southern shores of Cook Strait are the Pelorus (40), Motueka (75), Takaka (45), and Aorere (45), great structural faults being chiefly responsible for the position and characteristic features of the valleys of the last two.

An important commercial aspect of our rivers is their use not only as drainage channels, but as a source of water for pastoral purposes. Hardly any area is without water for stock or with a subsoil wanting in moisture necessary for successful cultivation. Only in Central Otago and on the Canterbury Plains were there formerly wide stretches of arid country, but the deficiency in the water-supply has been remedied by well-engineered systems of races, tapping unfailing streams at higher levels, and distributing a portion of their contents far and wide, so that the districts mentioned are rendered highly productive and absolutely protected from the serious effects of drought. It is, however, the rich alluvial flats and well-drained terrace lands bordering on the rivers that contribute specially to the high average yield per acre year after year for which this country has such a world-wide reputation.

From the brief summary given above it will be evident also that in her rivers the country possesses enormous stores of energy awaiting exploitation. A beginning has been made in some places, such as at Waipori in Otago, at Lake Coleridge in Canterbury, at the Horahora Falls and at Arapuni on the Waikato River, at Mangahao in Wellington, at Lake Waikaremoana, and at a few other places where there are minor installations. These owe their development to their comparative nearness to centres of industry; but they represent an infinitesimal portion of the energy available, and the value of our vast store will be more truly appreciated when our somewhat limited reserves of coal show signs of failure or become difficult to work—unless, indeed, some new form of power is disclosed by the researches of science in the near future.

The following article on the lakes of New Zealand is also by Professor R. Speight:—

Lakes are features of the landscape which are usually attributable to the filling up of hollows formed by faulting or warping, or by volcanic explosions, or by the irregular accumulation of material round volcanic vents, or to the interference with river-valleys by glaciers. Seeing that all these agencies have operated on an extensive scale in New Zealand in comparatively recent geological times, it is not surprising that its lake systems are well developed. The remarkable group of lakes lying in the middle of the North Island, as well as isolated enclosed sheets of water in other parts of the Auckland Provincial District, are due to volcanic action in its various forms, while those in the South Island are to be credited to the operations of glaciers. We have therefore two distinct types of lake scenery—one for each Island. The relief of the land near the volcanic lakes is not by any means marked, and they therefore rarely have bold and precipitous shores, and their scenic interest depends partly on the patches of subtropical bush which grows luxuriantly in places on the weathered igneous material, and partly on their desolate and forbidding surroundings, everywhere reminiscent of volcanic action, where the softening hand of time has not reduced the outpourings of the eruptive centres to a condition favourable for the establishment of vegetation. The thermal activity which is manifested in numerous places on their shores adds to their interest. In the South Island the lakes lie in the midst of splendid mountain scenery, with amphitheatres of noble peaks at their heads, crowned with perpetual snow, and clad at lower levels with dark primeval beech forest, which affords an appropriate setting for the waters at their base, rendered milky-white at times with the finest of sediment worn from solid rocks by powerful glaciers, and swept down to the quiet waters of the lake by turbulent glacial torrents.

The following article on the geology of New Zealand was prepared by Dr. J. Henderson, M.A., F.N.Z. Inst., Director of the Geological Survey:—

The following article dealing with earthquakes in New Zealand has been prepared by Dr. C. E. Adams, F.R.A.S., Government Astronomer and Seismologist, with the assistance of Dr. J. Henderson, Director of the Geological Survey.

Earthquake and volcanic activity are manifestations of the adjustments constantly occurring in the earth's crust. In the not far distant past, geologically speaking, a more or less continuous belt of mountains was raised up round the border of the great sunken area of the Pacific, and this belt as a whole is characterized by "chronic and acute seismicity." At times the earthquakes occur within the belt itself, though a large proportion have their epicentres on its submerged frontal slope.

The South Island of New Zealand and the eastern part of the North are on the crest of the great mountain ridge or crustal fold which forms a portion of the real border of the Pacific. This ridge maintains a relatively straight course north-north-east for 1,600 miles, nearly to Samoa. The Auckland Peninsula, part of a decidedly weaker fold, meets the main fold nearly at right angles in the Rotorua-Taupo volcanic region. The earthquakes of this seismically sensitive district, though they may be locally severe, are not usually felt far from their points of origin. On the other hand, the tectonic earthquakes that occur along the main earth-fold shake large areas, some of them being recorded on instruments throughout the world. These are caused by the slipping of earth-blocks against their neighbours along fractures, and, fortunately for New Zealand, the most severe earthquakes have their origin along the great shears that probably cut the submerged flank of the main fold about 200 miles east of the North Island. The crest in New Zealand is not straight or simply curved and the elevation is not constant; elongated uplifted areas, most of them in linear series though some overlap, form a continuous ridge.

Many great faults and fault-zones have been traced for long distances, but a few only have been active since European occupation. Movement along a north-trending fault seven miles west of Murchison raised the ground east of the fault about 15 ft., and caused it to shift north-west about 9 ft. The uplift gradually decreases eastward, and dies out sixteen miles from the fault, facts indicating a slight tilt of the earth-block toward the east. Recent levellings show that the block is sinking somewhat irregularly, a movement, no doubt, causing some of the innumerable local after-shocks still being felt in the area. Other sensible earth-movements occurred in connection with the Taupo earthquake series of 1922,^* the Amuri earthquake of 1888,^† the Wellington earthquake of 1855,^‡ and probably the Awatere earthquake of 1848.§ There is also definite evidence of geologically recent differential movement of earth-blocks at several widely separated points in both Islands.

The origins of the New Zealand seismic region will be seen to arrange themselves in groups as follows:—

* P. G. Morgan: N.Z. Geological Survey; Annual Report for the year 1923, p. 10.

† Alexander McKay: Reports of Geological Explorations during 1888–89. Wellington, 1890.

‡ New Zealand Government Gazette, Wellington, vol. 2, No. 14, 17th October, 1855, p. 116. Sir Charles Lyell, "The Principles of Geology," tenth edition, 1868, vol. 2, p. 82. London: John. Murray. § New Zealand Government Gazette, Auckland, vol. 1, No. 27, 13th November, 1848. and vol. 1, No. 29, 20th November, 1848. H. S. Chapman in Westminster Review, vol. 51, 1849.

Group I.—Earthquakes felt most strongly on south-east coast of North Island; the origins form a strip 180 miles from the coast, parallel to the axis of New Zealand, and to axis of folding of older rocks in Hawke's Bay. Chief shocks: 17th August, 1868; 7th March, 1890; 23rd and 29th July, 1904; 9th August, 1904 (intensity IX on R.-F. scale); 8th September, 1904; prob. 23rd February, 1863 (IX, R.-F.); &c.

According to the late Captain F. W. Hutton, F.R.S., the geological evidence shows that New Zealand rose considerably in the older Pliocene period, and was then probably joined to the Chatham Islands. At a later period subsidence occurred, followed again by elevation in the Pleistocene period, with oscillations of level since. The seismic origins of this group are at the foot of a sloping submarine plateau, about two hundred miles wide, which culminates to the east-south-east in the Chatham Islands. This elevation is separated from the New Zealand coast by a trough from 1,000 to 2,000 fathoms in depth, which is widest and deepest between these origins and the mainland.

Group II.—(a) South-east of Otago Peninsula. Shocks: 20th November, 1872, &c.

(b) A strip south-east of Oamaru. Shocks: February, 1876; April, 1876; &c.

(c) Many short and jerky, but generally harmless, quakes felt in Christchurch. Banks Peninsula, and mid-Canterbury. Chief shocks: 31st August, 1876; 27th December, 1888 (VII, R.-F.); &c. Focus of 1888 shock, sixteen miles long, from west-south-west to east-north-east, twenty-four to twenty-five miles below surface, being the deepest ascertained origin in the New Zealand region.

These origins form a line parallel to the general axis of the land. It is possible that the loading of the sea-floor by the detritus brought down by the rivers of Canterbury and Otago is a contributing cause of the earthquakes of this group.

Group III.—Wellington earthquakes of January, 1855, and Cheviot earthquakes of 16th November, 1901, and of 25th December, 1922 (VIII, R.-F.).

The origin of the earthquake of 1855 was probably the fault that forms the eastern boundary of the Rimutaka Range and the western boundary of the Wairarapa Valley.

The origin of the Cheviot earthquake of 1901 was probably in or near the southern continuation of this fault.

The great earthquakes of October, 1848, probably came from the same region as those of January, 1855. The chief shocks of both series did extensive damage to property, and caused the formation of large rifts in the earth's surface.

Group IV.—(a) Region about twenty-five to thirty miles in length, and ten miles or less in width, running nearly north-north-east from middle of Lake Sumner, about twenty miles below the surface, whence proceed most of the serer shocks felt from Christchurch to the Amuri, and a large number of minor shocks. Chief earthquakes: 1st February, 1868; 27th August to 1st September, 1871; 14th September and 21st October, 1878; 11th April, 1884; 5th December, 1881 (VIII, R.-F.), when Christchurch Cathedral spire was slightly injured; 1st September, 1888 (IX, R.-F.), when upper part of same spire fell, and still more severe damage was done in the Amuri district; 9th March, 1929 (IX, R.-F.).

(b) A small shallow origin not more than five to ten miles below the surface, a few miles south of Nelson. Earthquake: 12th February, 1893 (VIII to IX, R.-F.); chimneys thrown down and buildings injured.

(c) Origin in Cook Strait, north-north-east of Stephen Island, about ten miles wide, and apparently traceable with few interruptions nearly to mouth of Wanganui River; depth, fifteen miles or more. More than half the earthquakes recorded in New Zealand belong to this region; earthquake of 8th December, 1897 (VIII to IX, R.-F.). and other severer ones came from south-south-west end. Probably the first recorded New Zealand earthquake, felt by Captain Furneaux on the 11th May, 1773, belonged to this region. Also 8th May, 1929 (VIII, R.-F.), and 29th May, 1929 (VII, R.-F.).

(d) Taupo Earthquakes.—During June and July, 1922, earthquakes were almost continuous in the Taupo district. The shocks reached intensity VIII on the Rossi-Forel scale, and then gradually subsided. Conditions were practically normal by the end of the year. The shocks were restricted to a small area of country, and were felt most strongly at Taupo, Wairakei, and Oruanui. The disturbances were accompanied by loud rumblings. No effect appears to have been produced on the thermal activities of the region. Considerable subsidence was reported along the north side of Lake Taupo in a general north-easterly direction.

Former smart shocks in this region were reported in September-October, 1897.

(e) Morrinsville Earthquakes.—During November and December, 1926, earthquakes similar to the Taupo ones of 1922 were felt in and around Morrinsville. The earthquakes were apparently of shallow origin, and were probably caused by a movement along a fault trending west-north-west on the eastern side of the Pakaroa Range. The average intensity of the shocks was about IV, although one shock reached VIII on the Rossi-Forel scale. As in the case of the Taupo earthquakes, there was no evidence of any variation in the thermal activities of the district.

(f) An origin near Mount Tarawera, with a large number of moderate or slight shocks, most, but not all, volcanic and local in character—e.g., those of September, 1866, and those of June, 1886, which accompanied and followed the well-known eruption of Mount Tarawera.

These origins of Group IV are nearly in a straight line on the map; on or near the same line are the origins of earthquakes felt in the Southern Lakes District (15th December, 1883, &c.), the volcanoes Ruapehu, Ngauruhoe, Tongariro, Tarawera, and White Island. It is evident that this line, which, like the rest, is parallel or nearly so to the general axis, is a line of weakness or of unstable equilibrium. Hence the adjusting movements that have caused earthquakes may have from time to time relieved the pressure of the rocks that restrained overheated steam and other volcanic agents from bursting out, and so may have led to volcanic eruptions; just as the series of earthquakes in Guatemala and in the Caribbean Sea in April and May, 1902, were the signs of movements in the great folds of that part of the earth's crust, in the course of which, the pressure in the Antillean Ridge being relieved, the volcanic forces below Mount Pelée in Martinique, and Mount Souffrière in St. Vincent, caused the disastrous eruptions of that year.

Group V.—Off the west coast of the North Island near Raglan and Kawhia. Chief shock: 24th June, 1891 (VII to VIII, R.-F.). The line joining this origin to that of the earthquake of 1st February, 1882, is parallel to the other lines of origin (Groups I to IV); but we have no data to establish any connection between them.

The following article on the climate of New Zealand has been prepared by Dr. E. Kidson, O.B.E., D.Sc., F.N.Z.Inst., Director of Meteorological Services:—

Owing to the necessity for economy, it has not been possible to allot the customary space to the article on the climate of New Zealand. It was, therefore, decided to confine the present note to a brief discussion of certain aspects of the subject. Those requiring more general information may refer to the volumes of the Year-book which immediately precede this.

Rainfall.—Of all the climatic elements, rainfall is the one regarding which information is earliest and most frequently sought, since both one's comfort and the productivity of the soil depend so directly upon it. The distribution of annual rainfall in New Zealand is shown in the accompanying map. The control by topography is very conspicuous. Generally speaking, the more directly a locality is exposed to the prevailing westerly or north-westerly winds and the greater the altitude above sea-level, the greater the rainfall.

But, in addition to the total fall, we wish to know how the rainfall varies throughout the year. In this respect the regimes in various parts of the Dominion differ considerably. Monthly rainfalls for a few typical stations are given in Table 1. In the part of the Auckland Province north (roughly) of Kawhia and Tauranga, on the eastern side of the main range from East Cape to Wellington,

about Tasman and Golden Bays, and in Marlborough and North Canterbury, the rainfall is much heavier in winter than in summer. May, June, and July are the wettest and November, December, January, and February the driest months. This type of annual variation is shown by Auckland, Napier, and, to a less extent, by Christchurch. The farther south one goes, the less marked does the tendency for the heaviest rain to fall in winter become.

At Hokitika, which is fairly typical of all the western districts of the South Island, the distribution is very different. The rainfall is highest in spring, October being the wettest month, rather high in the autumn, lowest in February, and low also in winter. The reason for this is that the rain is brought by winds from a westerly quarter which have an annual variation of the type described. In the western districts of the North Island, as at New Plymouth and Wellington, the variation is a combination of the first and second types.

The third type of variation occurs in Canterbury and Otago, especially the interior portions. It is illustrated by the figures for Peel Forest in Table 1. Peel Forest is in the interior of South Canterbury. The rainfall in this type is heaviest in summer and lightest in winter. This fact is of great economic importance, because in most of the area concerned the rainfall is low. The distribution throughout the year is the most favourable for producing a good yield from the soil.

The number of days on which rain falls is an important factor in climate, as well as the amount. Table 2 gives the average number of days with rain in each month for some representative stations. A day with rain is one on which 0.005 inch or more is measured. Generally speaking, there is a fairly close relationship in New Zealand between the amount of rain and the number of rain days, but the latter is not directly proportional to the rainfall. There are considerable areas on the west coast of the South Island, for instance, which have ten or more times as much rain as the driest portions of the interior, but only about double the number of rain days. Marlborough seems to have a small number of wet days compared with its rainfall. To the south of New Zealand there is a rapid increase in cloudiness, showers fall with great frequency, and the number of rain days becomes high. This effect begins to be felt at Stewart Island, as can be seen from the data for Half-moon Bay.

Temperature.—Temperature is no less important than rainfall in determining the living conditions of a country and the yield from its soil. The specification of the temperature of a place is, however, not so simple a matter as might appear. Many different factors are involved in the determination of the precise temperatures experienced in any locality. The sea, for instance, responds very slowly to both daily and yearly changes in the amount of heat received from the sun, while on the land the response is rapid. Consequently, the nearer a station is to the sea the smaller are its daily and yearly fluctuations of temperature. Again, on plain country the air tends to stagnate, especially at night. At night time the surface layer cools rapidly through radiation from the ground, while during the day it becomes heated by the sun. There is less stagnation in the warm layer of the daytime than in the cold layer of the night. Consequently, stations on level plains or plateaux tend to be subject to frost and to have a relatively low mean temperature. On hill slopes the cold air flows away to lower levels as it is formed. In windy places, also, the air is prevented from stagnation. Frosts, therefore, are less frequent in such positions than at plain stations, and the mean temperature, if we allow for altitude, is higher. Allowance must be made for altitude, because it is found that the higher we go in the atmosphere the lower does the temperature become. In temperate latitudes the fall is about 9° F. per kilometre. It is not fair, therefore, to compare temperatures recorded at Thorndon, which was 12 ft. above sea-level, with those at the present Wellington meteorological station at Kelburn, which is at an altitude of 415 ft. To make temperatures comparable, the practice is frequently adopted of adding a correction for altitude at the rate of 9° F. per kilometre, or approximately 2°.7 F. per 1,000 ft. This has been done in Table 3. The Rotorua values, for example, have been increased by 2°.5 F., the station being 925 ft. above sea-level.

In all New Zealand publications it has been the practice hitherto to derive monthly mean temperatures from the means of the daily maximum and minimum. But, even on the average, the mean of the maximum and minimum differs slightly from the true mean for the day. The correction to the mean for the day has been determined approximately at Wellington from the records of thermographs.

In Table 3, therefore, the temperatures are reduced to sea-level and mean of day. For the remainder of the temperature tables the observed readings have been used without correction. All are in Fahrenheit degrees.

The stations given in Table 3 were chosen to show the effect of changing latitude, the difference between the east and west coasts in the South Island, and the difference between coastal and inland stations. Ophir is in Central Otago, where the nearest approach is made to continental conditions of any district in New Zealand.

The accompanying tables (Nos. 4 to 9) relate to temperature extremes. The first line gives the average of the maximum temperatures as observed each day, the second the average of the highest temperatures observed in each month and the year, and the third the highest yet recorded. Corresponding information regarding minimum temperatures follows. Next comes the average number of days on which the minimum temperature in the thermometer screen falls to 32° F. or below. This gives some idea of the susceptibility to severe frosts, such as would affect fruit trees. The last line gives the number of ground frosts. According to the British convention, a ground frost is recorded when the grass minimum thermometer falls below 30.4° F., damage being unlikely at higher temperatures. In the preparation of these tables some of the older records have, for various reasons, been discarded.

Sunshine.—The next most important element is sunshine. There is no doubt that New Zealand's greatest asset is its climate, and the outstanding feature of the climate is that, in spite of a high average rainfall and rather windy conditions, the proportion of sunshine is everywhere high. There must be few places in temperate latitudes which, while having a rainfall of over 116 in., experience as much sunshine as does Hokitika. The average amount of sunshine in each month and the year is given for eighteen places with fairly long records in Table 10. The greatest amounts are recorded at places which are protected by high mountain ranges as, for instance, at Nelson and Napier. A short record for Lake Tekapo, in the Mackenzie Country of Canterbury, indicates that conditions there are little, if at all, inferior to those at Nelson and Napier.

In Tables 11 to 15 will be found information regarding the frequency of occurrence of various phenomena.

Fog.—The best means of recording fog, and the one now generally adopted, is to measure the horizontal visibility at regular intervals. A fog is regarded as occurring when the visibility is less than one kilometre (1,100 yards). Visibility observations are not available for most places in New Zealand. Table 11 will, however, give some idea of the frequency of occurrence of fog. New Zealand is comparatively free from fog, especially fog of long duration. The most widespread and persistent fogs occur during the approach of cyclonic depressions. The record for Rangiahua, on Hokianga Harbour, is included in Table 11 to illustrate the frequency of fog on some of the landlocked harbours and estuaries of North Auckland.

Snowfall.—Snow is rare at sea - level, especially in the North Island. It is more frequent in the interior and at high altitudes. In eastern districts from Canterbury southwards it lies on the ground occasionally, even at sea - level. An entry of 0.0 in Table 12 indicates that snow has been recorded, but that the frequency was not more than 0.05 day. A similar practice is adopted in the subsequent tables.

Hail.—Hail is experienced more frequently as the latitude increases and on the west coast than on the east. It occurs more often in spring than at other times of year. The majority of the hailstorms recorded, however, are harmless, the stones being quite small. Occasionally, severe hailstorms are experienced in New Zealand, the stones reaching a diameter of from 1/2 in. upwards. These are usually associated with thunderstorms, and are probably quite as numerous on the east coast as the west and in the North Island as in the South.

Thunder.—Thunderstorms are more numerous in the North than in the South and on the west than on the east side of the main ranges. They are very rare in eastern districts in winter.

Strong Winds.—The figures in Table 15 include a proportion of high winds (force 7 on the Beaufort scale) as well as gales (force 8 and over). The figures for Wellington show the effect of the concentration of the winds through Cook Strait.