THE NEW ZEALAND OFFICIAL YEAR-BOOK, 1941

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-westerly-north-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 clown by the rivers being spread along the coast by ocean currents. The mountainous nature of the country makes the haulage of goods to and from the better-equipped natural harbours both costly and difficult, and the construction and maintenance 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.

As 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 cast 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 the 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.

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 cast 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.^††

* 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.

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^†:—