THE NEW ZEALAND OFFICIAL YEAR-BOOK, 1940

By reason of its elongated shape, New Zealand possesses a very lengthy coast-line in proportion to its area. With the exception of the low-lying North Auckland peninsula, the length of the New Zealand land-mass lies along a south-westerlynorth-easterly axis, and is thus parallel to the direction of its mountain-chains.

By reason of the latter fact the coast-line is, on the whole, not greatly indented; and, as a consequence, New Zealand is not well endowed with natural harbours. In the North Island, Auckland and Wellington are the only two safe natural harbours of which the fullest commercial use can be made. On the east coast of the North Auckland peninsula several deep and sheltered harbours exist, but as the surrounding country is comparatively undeveloped and the area somewhat remote they are of little economic consequence at present. In the South Island the Marlborough Sounds and the West Coast Sounds form perfect land-locked harbours, but owing to their situations and to the rugged nature of the terrain they have—with the exception of Queen Charlotte Sound—little or no commercial utility. Where vital localities have not been endowed with ideal harbours it has been necessary to improve existing facilities by dredging and by breakwater-construction, &c. In this manner efficient ports, capable of accommodating overseas vessels, have been formed in Lyttelton, Otago, and Bluff harbours. On the west coast of both Islands the strong ocean-drifts and high seas cause shoaling at river-mouths and harbour-entrances, while on the east coast of the South Island similar circumstances prevail, due to the large quantities of shingle brought down by the rivers being spread along the coast by ocean currents.

Since the mountainous nature of the country makes the haulage of goods to and from the better-equipped natural harbours both costly and difficult, the construction of further ports at various points along the coasts of both Islands has been necessary, either by dredging river-mouths or by harbour-construction work.

The mountainous nature of New Zealand is one of its most striking physical characteristics. In the North Island the higher 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 volcanoes include Mount Tarawera and White Island, each of which has, upon one occasion within historical times, erupted with disastrous consequences. Closely connected with the volcanic system are the multitudinous hot springs and geysers.

The South Island is much more mountainous than the North, but shows fewer manifestations of recent volcanic activity. Along almost the entire length of the Island runs the massive chain known as the Southern Alps, which attains its greatest height in Mount Cook (12,349 ft.), while no fewer than seventeen peaks exceed 10,000 ft.

The position and trend of the mountains in New Zealand exert considerable influence on the economic life of the Dominion. Attention has already been drawn to the relation between the direction of the mountains and the nature of the coast-line, while in the article dealing with climate (post) mention is made of the effect of mountains on climatic conditions.

At, may be expected, the higher mountains of the South Island have exerted a greater influence on the economic development of the country than those of the North Island. For many years the Southern Alps were an effective barrier to communication by land between the east and west coasts, while their climatic effects on the Canterbury plains and Otago plateaux determined the types of cultivation undertaken. Moreover, the existence of much elevated open country led to the development of pastoral holdings on a large scale. While the mountains in the North Island are not as high nor as extensive as those of the South Island, in the early days they effectively isolated various portions of the coastal plains and valleys. Their effect on climatic conditions, however, is considerably less, the rainfall being more evenly distributed. Due to this more even distribution of the rainfall, and to the existence of considerable areas of lower relief, the foothills of the mountain systems were heavily wooded, and so proved a hindrance to agrarian development.

In the 1931 issue of the Year-Book was given a list, not claimed as exhaustive, of 223 named peaks of 7,500 ft. or more in altitude. Below is a list of the peaks, restricted to the three largest volcanic cones in the North Island and to mountains of a minimum height of 9,000 ft. in the South Island. The list has been compiled from various sources, and does not purport to be free from omissions.

In keeping with the dimensions of her mountain system, New Zealand possesses, in the South Island, a glacial system of some magnitude. Of the glaciers the largest is the Tasman, which, with others of comparable size, rises in the more elevated area surrounding Mount Cook. Flowing down the eastern slope of the range, this glacier has a length of 18 miles and a width of 1¼ miles. In common with other glaciers on the eastern slope, of which the more important are the Murchison (11 miles), the Mueller (8 miles), the Godley (8 miles), and the Hooker (7¼ miles), its rate of flow is slow, while its terminal face is at an altitude of somewhat over 2,000 ft. On the western slope of the range, owing to the greater snow precipitation, the glaciers are more numerous and descend to lower levels, while the steeper slope gives them a faster rate of flow. The two largest of these are the Fox and the Franz Josef, with lengths of 9¾ miles and 8½ miles respectively, and terminal faces at altitudes of 670 ft. and 690 ft.

As will be realized, these glaciers are an important tourist attraction, and as such have definite economic significance. Moreover, those glaciers on the eastern slopes which feed rivers utilized for irrigation and hydro-electric purposes are valuable in that they help to ensure a steady volume of water in such rivers.

Of the numerous New Zealand rivers few are of sufficient length or volume to be navigable. Moreover, owing to the high relief of the country, they are mostly swift-flowing, while, as mentioned previously, nearly all are obstructed at their mouths by bars. For the purpose of internal communication, therefore, they are of little economic utility, and only in two or three isolated instances have they been thus consistently used. With improved roading conditions, however, their traffic has become negligible even in these cases.

As sources of hydro-electric power, New Zealand rivers are of considerable importance, since their rapid rate of flow and dependable volume of ice-free water make them eminently suitable for this purpose. At the present time the Waikato and the Mangahao rivers in the North Island and the Waitaki River in the South are used for major hydro-electric schemes. The characteristics just mentioned are also important for purposes of irrigation, but, owing to the country's reliable rainfall, there are few areas other than in Canterbury and Otago where the rivers are so utilized.

In the 1932 Year-Book appears an account of the rivers of New Zealand by Professor R. Speight, M.Sc., F.G.S., Curator of the Canterbury Museum.

Space in this issue is, however, available only for a list of the more important rivers, with their approximate lengths, the latter being supplied by the Department of Lands and Survey. Figures in parentheses indicating the approximate discharge, in cubic feet per minute, are shown for the largest rivers.

The discovery in 1861 that the beds of numerous rivers in the South Island contained extensive deposits of alluvial gold was of considerable importance in the economic development of the country. Not only did it lead to an increase in population and in wealth, but, through the following of the numerous streams to their sources, it also led to the rapid exploration of large tracts of remote country. The exploitation of these deposits has been carried on with varying degrees of success up to the present time by both manual and mechanical means.

A further factor in connection with rivers is that, owing to the very successful acclimatization of fresh-water fish, notably trout, many of them now provide exceptionally fine fishing.

In considering New Zealand's numerous lakes, a distinction can be made, especially from the scenic viewpoint, between the lakes of the two Islands. Surrounded by extremely rugged country the larger lakes of the South Island are distinguished by the grandeur of their alpine settings, while those of the North Island, situated on a volcanic plateau, are of interest by reason of the neighbouring thermal activity. Due to the excellence of their fishing, the latter possess an added tourist attraction. In both Islands the larger lakes are situated at high altitudes, and their consequent remoteness renders them unsuitable as a means of communication. In their functions as reservoirs the lakes of both Islands are of vital importance for the maintenance of the streams draining them and as a means of flood-prevention. More especially is this the case where hydro-electric schemes are involved, Lakes Waikaremoana and Taupo in the North Island, and Lakes Coleridge, Pukaki, and Tekapo in the South Island, being of particular significance in this respect.

A detailed article on the lakes of New Zealand, also by Professor R. Speight, will be found in the 1932 Year-Book. The more important lakes are stated below.

New Zealand is a small country, but its geological history is as complex and as ancient as that of a continent. Land, though from age to age it varied greatly in area, outline, and elevation, must have persisted in the New Zealand area from the oldest Palæozoic or earlier. Long periods—during which gentle regional oscillations and warpings, aided by the slow-acting forces of denudation, brought about gradual changes—were interrupted by great revolutions when earth-stresses ridged the crust into mountains and quickly altered the whole configuration of the land and sea-floor. For New Zealand the important geological periods are those that followed the two latest mountain-building movements—the Kaikoura deformation of late Tertiary time, and the Hokonui deformation of the early Cretaceous. The deposits laid down in the intervening period of relative crustal stability cover a large proportion of the land, and contain all the coal and most of the limestone of the Dominion. The soils on which grow the forests, pastures, and crops are of post-Tertiary age, and the great bulk of the gold has been won from deposits formed during the same period.

The oldest known fossiliferous rocks in New Zealand are the Ordovician slates and greywackes of west Nelson and south-west Otago. Lower unfossiliferous beds of the same great system extend southward from the northern area and outcrop in the Westport, Reefton, Greymouth, Ross, and Okarito districts. Above the fossil-bearing beds, but probably also of Ordovician age, are the black phyllites, quartzites, and marbles, which outcrop continuously from Takaka to Mount Owen, and are again exposed in the upper basins of the Matakitaki, Maruia, and Grey Rivers. The similar rocks of western Otago probably also belong to this group. The complex of gneisses and schists of the same region, intruded by acid and basic plutonics, and usually considered of Archæan age, resembles the part of the Ordovician strata of western Nelson that has been similarly invaded and metamorphosed and may well be of early Palæozoic age. Different authorities assign the mica, chlorite, and quartz schists of Central Otago to ages that range from the Archæan to the Triassic. They are certainly Palæozoic or older, since they grade upward into gréywackes that, at Clinton, contain Permian fossils.

Devonian rocks are certainly known only in the Baton, Wangapeka, and Reefton districts. These beds, fossils from which have lately been examined in England, cover only small areas. But the old Geological Survey mapped wide tracts of country in Nelson and Otago, covered with beds of the Te Anau Series, as Devonian, and the correlation may well be correct, though the rocks are entirely unfossiliferous.

The Maitai Series, which forms the ranges on the south-east side of the Nelson lowlands, is probably of Carboniferous or Permo-Carboniferous age. Their position in the time scale and their correlation with rocks in other parts of New Zealand have provoked much discussion. Permian strata, as already stated, occur in Otago, where the area they cover may be considerable.

Richly fossiliferous late Triassic rocks are known in the Kawhia-Mokau district, near the City of Nelson, and at several localities in Canterbury and Otago. Except in Nelson and Canterbury, strata that contain fossils referable to several stages of the Jurassic succeed without observed unconformity. The broad belt of greywacke and argillite that forms the mountains of Canterbury and Marlborough, and continues as a narrower belt through Wellington to northern Hawke's Bay, is usually referred to the Trias-Jura. Similar rocks outcrop in the centre of the North Island and at many points in North Auckland. There are Upper Triassic molluscs in these beds at several localities, and the vertebra of a saurian with Triassic rather than Permian affinities was found near Wellington. Lithologically the greywackes and argillites of this vast series differ somewhat from the rocks of similar type belonging to the Jurassic and Maitai series; they are therefore thought to be of older Triassic age, but may well range into the Permian. The schists occurring with them in the Kaimanawa, Kaikoura, Moorhouse, and Kirkliston Ranges are probably older.

The thick conglomerates conformably overlying the younger Jurassic shales of the Port Waikato, Kawhia, and Coromandel regions belong to either the youngest Jurassic or the oldest Cretaceous. Strata of early and middle Cretaceous age occur east of the main axis of New Zealand at several points from Marlborough to East Cape. Late Cretaceous beds are much more widely distributed, being known in North Auckland and in many localities along the eastern side of both Islands. They contain thick layers of black shale that give many indications of oil, which, however, has not yet been found in commercial amount. The oldest known workable coal-seams in New Zealand, those at Broken River, Malvern Hills, Shag Point, and Kaitangata, and perhaps some near Greymouth, are in young Cretaceous beds. Of the same age are the auriferous “cements” of the Tuapeka district that greatly enriched the gravels of the neighbouring streams and are themselves worked for gold.

Tertiary rocks form the greater part of the North Island and are widely distributed in the South. As a whole they are weaker and more readily weathered than the older strata, and hence have given rise to less rugged country, now mostly cleared and grassed and forming productive pastoral land.

Eocene rocks are present in North Auckland, and probably also in the Gisborne, Hawke's Bay, and east Wellington districts. In the South Island they occur on the West Coast and in Canterbury and Otago, in which regions they contain valuable coal-seams worked at Westport, Reefton, Greymouth, Mount Somers, and Milton.

In Oligocene time the maximum subsidence during the Tertiary occurred, and but little of the New Zealand area remained above sea-level at its close. The thick limestones of the Oamaru district and the contemporaneous limestone prominent in many parts of New Zealand are the younger deposits of this age. The older beds contain the extensive coal-measures of the North Auckland, Waikato, Charleston, Nightcaps, and other coalfields.

Miocene strata cover large areas in both islands, and also outcrop in the Mokau, Gisborne, and Hawke's Bay regions. In north Taranaki, the Murchison basin, and parts of the West Coast, thick coal-measures of this age contain workable seams of brown coal.

During the Pliocene the New Zealand area, which had been intermittently rising since the close of the Oligocene, was greatly elevated and deformed. The earth-blocks from which the present mountains have been carved were uplifted from, or from near, sea-level, and New Zealand as it now is was roughly shaped out. In the South Island the deposits of this period are chiefly gravels deposited in structural depressions; but in the North Island, and especially in its southern half, there are thick and extensive shoal-water marine sediments. These, and the underlying Miocene strata, are the source of the petroleum found at New Plymouth, and the lacustrine quartz conglomerates of Otago, probably of Pliocene age, have yielded much detrital gold.

The Pleistocene was a period of regional oscillation. While the land was high the mountains of the South Island were intensely glaciated, and great ice-streams, carrying vast bodies of debris, descended into the low country; after the highlands had been reduced in height through both denudation and decided subsidence the glaciers rapidly retreated, and are to-day represented by comparatively small remnants far in the mountains. While the ice was melting, the rivers of the South Island were unusually active in transporting waste to the lowlands and the sea. At this time, too, as well as somewhat earlier, the volcanoes of the North Island ejected an abundant supply of fragmentary material, much of which was borne away by the streams and used in building plains.

The deposits of Pleistocene and Recent age are in New Zealand of greater economic importance than those of all other ages. The plains, river-flats, and low-lands generally were formed or profoundly modified during this period, and the soils that cover them were produced. During the same time practically all the gold won from the gravels of the South Island was liberated from a hard matrix and concentrated into workable deposits, and the rich bonanzas of the lodes of Hauraki were formed by secondary enrichment. The land-oscillations of the period are also of economic importance, for New Zealand's abundant water-power is derived from streams that have not yet, owing to the recency of land-uplift, cut their valleys to grade. On the other hand, land-depression has provided harbours and valuable artesian basins in many parts of the Dominion.

Plutonic rocks intrude the Palæozoic and Mesozoic strata in many places, and some of the formations show evidence of contemporaneous volcanic action. Of the plutonic rocks granite is much the most prominent, and it outcrops at many points in west Nelson, Westland, Otago, and Stewart Island. In Nelson there were at least two periods of intrusion, probably corresponding with the great mountain-folding movements of the late Palæozoic and early Cretaceous times. The auriferous lodes of Reefton and other localities on the West Coast probably originated from the cooling magmas that formed the younger granites. Basic and ultra-basic rocks, the latter now largely altered to serpentine, occur in Nelson, Westland, Otago, and, to a less extent, in North Auckland.

Though volcanoes are known to have existed in Mesozoic and Palæozoic times, they seem to have been more active during the Tertiary than in any earlier age. The vast pile of flow and fragmental rocks that form the Hauraki Peninsula and the range that continues it southward to Tauranga belong to this period. The gold-silver veins extensively worked at Coromandel, Thames, and Waihi are in these rocks, which southward are smothered by the rhyolitic pumice that vents in the Taupo-Rotorua zone ejected during the late Pliocene and Pleistocene. Thick showers of pumice from this region cover a large part of the centre of the North Island, and streams have carried the finer material to practically all the low-lying parts of the Island. The volcanoes are still alive, as is evidenced by the steam-vents, hot springs, and geysers found in the depressed zone extending from Ruapehu to White Island. The volcanic rocks of Taranaki probably range from the Miocene to the Pleistocene in age. The basalts and scoria cones that occur so abundantly between Kawhia and the Bay of Islands belong for the most part to the late Pliocene and Pleistocene, though cones at Auckland City are probably Recent.

In the South Island the volcanoes appear to be quite dead, for the hot springs at Hanmer and near the alpine chain are due to other causes. In the middle Tertiary, however, there were outbursts at many points, the chief eruptions being at Banks Peninsula and about Dunedin.

In a short article it is impossible to give an adequate idea of what geological workers have accomplished in New Zealand, or of what they have yet to do in order that the wisest use may be made of the country's mineral and agricultural resources. For good general accounts the treatises of Professors Park and Marshall should be consulted, and for more detailed information the bulletins of the Geological Survey and the many papers that have appeared in the Transactions of the New Zealand Institute (now the Royal Society of New Zealand).

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 Island 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 across the floor of the Pacific, 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.

Many great fault-zones have been traced for long distances, but a few only have been active since European occupation. The Hawke's Bay earthquake of 1931 raised an area sixty miles long in a north-east direction and in parts ten miles wide. the uplift was greatest along the south-east edge of the area—for miles amounting to 6 ft. or more. Numerous levels on the Heretaunga Plain and along the railway north of Napier show that the uplift decreased north-westward, so that the area was slightly tilted in that direction. The ground east of the uplifted area sank, and parts of the Napier and Wairoa flats are over a foot lower than before the earthquake.

In 1929, movement along a north-trending fault seven miles west of Murchison raised the ground east of the fault by about 15 ft., and caused it to shift north-west by 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 felt in the area over many months. 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.

A comparison between the records of destructive earthquakes in New Zealand and similar records in other seismic countries shows that the seismicity of New Zealand in general is surprisingly high. This, however, is due to the occurrence of a large number of earthquakes of the semi-destructive type, with comparatively few of the disastrous type.

During the period 1835-1934 sixty-nine destructive earthquakes are known to have occurred in New Zealand, forty-nine of which were of the semi-destructive type (not exceeding intensity R.-F. 8). There were fourteen of intensity 9, and six of intensity 10.^‖ The distribution of earthquakes throughout New Zealand itself during the period 1848-1934 shows that the region of intense seismic activity, where earthquakes are frequent and occasionally severe, includes the eastern and southern parts of the North Island and the northern part of the South Island.^¶

The Auckland Peninsula, South Canterbury, and Eastern Otago appear to have been comparatively free from earthquakes during the past hundred years. Although the seismic history of the Fiord region of the South Island is not very well known, there are records of sealers having experienced violent earthquakes in those parts in 1792, 1810, and 1826-27.^** Also there is some record of violent earthquakes having occurred near Auckland in 1834-35.^††

It is thus evident that, although some parts of New Zealand have experienced no severe earthquakes during the past hundred years, no assurance can be given that none will occur there in the future.

The following table, compiled for some of the main centres in New Zealand, shows—(1) The mean annual frequency of all earthquakes during the period 1848-1934^¶; and (2) the number of destructive earthquakes during the period 1835-1934^‡‡:—

* 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, Wellington, Vol. 1, No. 27, 13th November, 1848, and Vol. 1, No. 29, 20th November, 1848. H. S. Chapman in Westminster Review, Vol. 51, 1849.

‖ L. Bastings: “Destructive Earthquakes in New Zealand, 1835-1934,” N.Z. Jour. Sci. & Tech., Vol. 17, No. 1, July, 1935. Dominion Observatory Bulletin 103.

¶ L. Bastings and R. C. Hayes: “Earthquake Distribution in New Zealand, 1848-1934,” N.Z. Jour. Sci. & Tech., Vol. 16, No. 5, March, 1935. Dominion Observatory Bulletin 95.

** R. McNab: “Murihiku and the Southern Islands” (1907). R. Taylor: “Te Ika a Maui,” London, 1855.

†† Australasian Association for the Advancement of Science, Vol. 3, 1891, p. 531.

‡‡ R. C. Hayes: “The Seismicity of New Zealand Cities and Towns,” N.Z. Jour, of Sci. & Tech., 1936. Dominion Observatory Bulletin 111.

Although there appears to be no regular annual variation in the frequency of New Zealand earthquakes, the mean monthly numbers over a long period indicate that earthquakes are on the average most frequent in March and least so in January. The mean monthly numbers follow approximately the mean annual variation of atmospheric pressure in New Zealand.^*

The total number of earthquakes reported felt in New Zealand, and the maximum intensities reported in each of the years 1921 to 1938 inclusive, were as follows:—

The figures in the above table, giving the number of reported earthquakes, require careful interpretation. In years of major earthquakes, such as 1929 and 1931, many of the numerous after-shocks are liable to be passed unnoticed, while during a period of quiescence there is a tendency for all shocks, however slight, to be reported. This leads to an undue emphasis being placed upon earthquake activity during a comparatively quiet period. The great number of earthquakes reported in 1922 is due to the swarm of local shocks which occurred in the Taupo region in the latter half of that year. Also, although there was no major earthquake in 1930, a large number of shocks occurred in that year, due mainly to the continuation of after-shocks of the Buller earthquake of 17th June, 1929.

During the period 1848-1938 the number of deaths recorded in New Zealand as due directly or indirectly to earthquakes was 284. Of these, 255 were due to the Hawke's Bay earthquake of 3rd February, 1931. A table giving details of the number of deaths due to earthquakes in New Zealand was published in the 1936 issue of the Year-Book.

Earthquakes in New Zealand are recorded by means of seismographs, and also by a system of non-instrumental reports. The main seismograph stations are located at the Dominion Observatory, Wellington, and the Magnetic Observatory, Christchurch. The Dominion Observatory acts as a central station for ten other subsidiary stations in New Zealand and one at the Chatham Islands. The subsidiary stations are operated by officers of other Government Departments, by Engineers of some of the Electric-power Boards, and by private individuals. The station at Apia, Samoa, is under the direct control of Apia Observatory.

The system of non-instrumental earthquake reports was inaugurated in 1888. At first it was confined to a selected number of telegraph-offices distributed throughout the Dominion, but in recent years more telegraph-offices have been added, and a number of lighthouse-keepers and several private observers have also taken up the work. There are at present 120 non-instrumental reporting stations. This system of recording earthquakes depends entirely on personal observations. Special forms are used, on which information is required concerning the observed time of an earthquake, the direction and duration of the movement, and any other particulars likely to be of value in estimating its intensity. The Dominion Observatory collects and summarizes all such reports of earthquakes felt in New Zealand.

*R. C. Hayes: “Earthquake Frequency in New Zealand,” N.Z. Jour. Sci. & Tech., Vol. 16, No. 5, 1935. Dominion Observatory Bulletin 104.

Information regarding earthquakes obtained from the seismograph records of all the New Zealand stations, and from the reports furnished by non-instrumental stations, is published in a monthly seismological bulletin. This bulletin includes provisional earthquake epicentres in New Zealand and in the south-west Pacific generally. The New Zealand epicentres are determined solely from the records and reports of the New Zealand stations, while the determination of those in other parts of the south-west Pacific requires the use of additional data from Apia, Papeete, and the Australian seismograph stations.

The Dominion Observatory also publishes special bulletins dealing with the results of research work in seismology. All seismological publications are distributed to the chief seismological stations and institutions throughout the world.

Seismic activity in New Zealand in 1938 was notable chiefly for a series of rather severe earthquakes towards the close of the year. Although the number of shocks felt was less than in 1937, the maximum intensity reported (R.-F. 8) was the highest since 1934. The activity in 1938 may be summarized as follows:—

The following list gives some particulars of the most important New Zealand earthquakes in 1938:—

A total of 132 shocks was reported felt during 1938, 80 of which were felt in some part of the North Island and 60 in some part of the South Island. Eight shocks were felt in both Islands. The maximum intensity was R.-F. 8, and this occurred in parts of southern Hawke's Bay and northern Wairarapa on 15th and 30th December.

The following is a monthly summary of earthquakes reported felt during 1938:—

The New Zealand Meteorological Office is situated at Wellington. Aviation-service stations are established also at Auckland and Christchurch (Wigram Aerodrome). General weather forecasts based on observations at 9 a.m. and 3 p.m. are issued at noon and 5 p.m. respectively. District forecasts are telegraphed at midday to certain of the principal seaports, where they are displayed at the post-offices, and are provided, also, to the leading newspapers. The evening forecast is published by the newspapers on the following morning. Weather reports intended primarily for aviators are transmitted from Station 2YA of the National Broadcasting Service at 6.50 a.m., 10 a.m., and 1 p.m. With the 1 p.m. issue is given the noon forecast for the Dominion and the Wellington District forecast. District forecasts are broadcast at 1 p.m. also from Stations 1YA, 3YA, and 4YA. In the late afternoon a special Dominion forecast for farmers is issued from each of the main centres. In the evening the Dominion forecast is broadcast once or twice from the four main centres, followed by district forecasts. The first issue from 2YA during the news session, which commences at 7 p.m., gives, in addition, weather reports from a series of observation stations distributed over the Dominion and the surrounding area.

Rainfall data from approximately four hundred stations are printed monthly in the New Zealand Gazette. Observations of temperature, pressure, sunshine, wind, &c., from about forty-five stations are published annually by the Meteorological Office. Papers on various aspects of the climate and weather of the Dominion are published from time to time as “Meteorological Office Notes.”

New Zealand lies wholly within the Temperate Zone, and it is also wholly and at all seasons within the zone of prevailing westerly winds though they are stronger and more persistent farther southward. Owing to its isolation and its narrowness in the direction of the prevailing winds, its climate is predominantly marine in character. Nevertheless, the modifications due to the height and continuity of the main ranges and the general high relief of the country are quite considerable, especially in the South Island. There is, for example, a very great variation in the rainfall from the western to the eastern side of the Southern Alps, and for so narrow a country, features of a continental type are rather strongly developed in the interior of the South Island. By breaking up the prevailing winds and causing the air at different levels to mix, mountains tend, also, to prevent the stratification of the air into layers of different density. Consequently very extensive and persistent cloud-sheets are seldom experienced. New Zealand therefore enjoys a high percentage of sunshine, a factor of great importance in the climate of a country with so high a rainfall.

The principal current in the surrounding ocean waters is from south-west to north-east. Off the west coast of the South Island, however, the current divides, one branch turning southwards to Foveaux Strait, while others pass through Cook Strait and round the northern extremity of the Dominion. The rather small range in climate from north to south is probably accounted for by this current.

According to the widely accepted classification of climates developed by W. Köppen, New Zealand has the climatic formula Cfb, denoting a cool-temperate moist climate without marked seasonal variations in temperature or precipitation. Under the same formula are classified southern Victoria and Tasmania and parts of southern Chile in the Southern Hemisphere, much of Europe, Japan and Korea, and a strip of the west coast of North America in the Northern Hemisphere. Generally, however, it is a climate characteristic of the ocean rather than the land areas of the Temperate Zone.

Tables 1 to 10 appearing in the following pages relate to varying, but usually lengthy, periods. In Table 11 the duration covered by the respective averages for that table is given.

Of all the climatic elements, probably the one that exerts the greatest influence on our lives is rainfall. It causes us much personal discomfort, but the production of the food by which we live depends directly on the availability of moisture from this source. Maps showing the distribution of mean annual rainfall appeared in issues of the Year-Book prior to 1934.

The controlling influence of topography on rainfall in New Zealand is very conspicuous. Areas exposed to the westerly winds have heavier rains than those protected from them by mountain ranges. Next, the greater the altitude the greater in general is the precipitation. There must be a limit beyond which precipitation begins to decrease again with altitude, but this has not yet been determined in this country. The indications are that precipitation is heaviest between 3,000 ft. and 4,000 ft. The annual total varies from about 13 in. at Galloway in Central Otago to over 200 in. in parts of the Southern Alps and on Mount Egmont.

The distribution of the precipitation throughout the year is little less important than its total amount, the effect of rainfall in winter, for example, being very different from that in summer. There are three principal factors controlling the annual variation of rainfall in New Zealand. The first of these is the proximity to the high-pressure belt in the subtropics. In this belt the rainfall year is divided into a dry summer and a wet winter season. We will call this distribution type A. As the distance from the high-pressure belt increases, the contrast between summer and winter decreases, so that by the time southern New Zealand is reached the variation due to this factor is small. The next most important factor is the influence of the prevailing westerly winds. These bring rains to the areas exposed to them, while areas which are protected from them by mountain ranges have little rain when the westerlies are blowing. Now, the westerly winds are strongest in spring, the maximum flow being in October. There is a temporary drop in February, followed by a partial recovery in the autumn, but the flow is least in winter. The régime of the westerly winds, therefore, tends to produce a second type of annual variation, type C, in which the rainfall is heaviest in spring, decreases somewhat in the late summer, increases again in the autumn, and decreases to a minimum in winter.

The third factor is the convection which takes place during periods of light winds, clear skies, and intense sunshine, especially when the preceding winds have brought cold air over the land from the south. After conditions of the type mentioned have endured for several days, the convection is likely to be so intense as to produce local showers. These are often heavy, sometimes accompanied by thunder, and occasionally of the nature of local cloud-bursts. Rainfall of this type is most common in the interior of continents. Being caused by solar radiation, it is most frequent when solar radiation is strongest—namely, in summer. According to type B, therefore, we would have a relatively wet summer and a dry winter.

A rainfall régime of type A in a fairly pure form is experienced in the part of the Auckland Province, north, roughly, of Kawhia and Tauranga, and on the eastern side of the main ranges from Cook Strait to East Cape. It is still dominant in the lower country about the Tasman and Golden Bays, and in Marlborough and North Canterbury. Type C is developed strongly in Westland and the south-west Fiord country. It is shown fairly well by Hokitika, but much more distinctly if the data for a number of West Coast stations be combined. It is dominant in the far South, in the mountains of Nelson, and in the portion of the North Island not yet referred to. In this latter area, however, types A and C combine in varying proportions. Most districts show the effect of the westerly winds in a relatively high rainfall in October, but this is least noticeable in the low country east of the main ranges. The areas where type C dominates are those with the heaviest rainfall. Type B is dominant in the interior and southern portions of Canterbury and the central and eastern portions of Otago, and is especially characteristic of the dry areas of the provinces mentioned. The summer rains of this type are of great importance to the farming communities in the interior of Canterbury and Otago. The régime of annual rainfall experienced had an important influence in determining the nature of the primitive vegetation in the various districts.

Next to the amount and the annual variation of precipitation, the frequency with which it falls is its most important characteristic. In Table 2 the average number of days with rain in each month is given for some representative stations. A day with rain is one on which 0.005 in. 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. New Zealand is extremely fortunate in that, even where the rainfall is very heavy, intervals between rains are almost everywhere sufficiently frequent and prolonged to ensure adequate drainage, while there is enough sunshine to dry the soil surface. Otherwise, large areas in the west and south would be covered with peat.

Temperature is no less important than rainfall in determining the living conditions of a country and the yield from its soil. But it is much less variable, and in the Southern Hemisphere especially, is largely determined by latitude. Its influence is therefore taken much more for granted. 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. It is to this effect that the principal difference between a continental and a marine climate is due. Although New Zealand is narrow, the high ranges shield the country to the east of them to a considerable extent, so that there is a nearer approach to continental conditions than would otherwise be expected, particularly in the interior of Canterbury and Otago. 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. The effect is accentuated near the slopes of hills because the cold air flows away down the slopes to lower levels. The hills, therefore, gain freedom from frost at the expense of the plains. In windy situations, also, the susceptibility to frost is lowered owing to the prevention of stagnation. Apart from the effects due to air-drainage and windiness, the temperature decreases with altitude. In temperate latitudes the fall is about 9° F. per kilometre. It is unsound, therefore, to compare, for example, temperatures recorded at Thorndon, Wellington, which was only 12 ft. above sea-level, with those at the present meteorological station at Kelburn, which is at an altitude of 415 ft., without making allowance for this difference in altitude. Such a procedure would lead to the erroneous conclusion that the climate had become colder. If charts of mean temperature are to be prepared it is clear that they will be very complicated, especially in a mountainous country like New Zealand, owing to this effect of altitude. It is usual, therefore, to simplify matters by applying a correction 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. If the actual temperature is required, it can be found by reversing this process.

In New Zealand publications it has been the general practice 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 from the records of thermographs with fair accuracy at Wellington and more roughly at several other places.

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.