THE REGION OF LAKE TAUPO.

Natural phenomena—The great table-land—Position and dimensions of the lake—Watershed—Geological features—The lake an extinct crater—Crater lakes—Areas of thermal action.

As during my journey through the King Country the widely extended region surrounding Lake Taupo will of necessity be brought prominently forward as being the principal centre around which my explorations were prosecuted, I will endeavour to define in general terms the leading features of this important area, in order that all my future descriptions of the country traversed may be more readily understood by the general reader.

This portion of the North Island, by reason of the varied features of its natural phenomena, is without doubt one of the most wonderful and interesting fields for geographical exploration and geological research to be found in any part of the world. It is, in fact, a portion of the earth where some of the most marvellous works which mark the progress of a Divine Creation may be viewed in singular and varied contrast, and while one beholds in wonder the stupendous action of volcanic fires, one may trace the no less potent force of the snowy glacier and bounding river. Here nature, with her mighty forces of fire and water, has formed and moulded a region of extended plains pierced by colossal mountains which raise their giant heads to the region of eternal snow, while countless rivers pour down their waters into a lake possessing the dimensions of an inland sea.

TRANSVERSE SECTION

: TRANSVERSE SECTION OF NORTH ISLAND FROM S.W. TO N.E.
AA. S.W. fall of great central table-land to coast, geological formation near surface, pumicious grit and decomposed trachytic rock, in form of light earth, resting on strata of pumice and fluvial drift. Vegetation various native grasses, low fern and forest.
B. Onetapu scoria desert, highest point of table-land, dividing northern and southern watershed.
CC. Sources of Whangaehu and Waikato rivers, flowing south and north respectively.
DD. Centres of volcanic upheaval.
EE. General direction of great pumice deposit, forming extensive open plains. Vegetation principally tussock grass and manuka scrub.

The middle portion of the North Island is formed of an extended table-land, which towards its central point, that is to say, in the vicinity of the lake margin, attains to a mean altitude of nearly 2000 feet above the level of the sea. Beyond this radius, which I may term the inner circle of the great lake basin, the plane of elevation varies in altitude, and attains its highest point at its southern division, where, on the Onetapu desert, at the eastern base of the great mountain Ruapehu, it rises to a height of over 3000 feet, from which place it inclines gradually towards the south coast, and divides the northern and southern watershed of this portion of the country. Easterly of this the table-land is intersected by the Kaimanawa mountains, and from the western base of Ruapehu it falls with a rapid descent into the valley of the Whanganui. To the north of the lake, along the upper valley of the Waikato, it has an average elevation of from 1500 to nearly 2000 feet, until it descends into a broad valley near Atea-amuri, where the river flows round to the north-west to enter the plains of the lower valley of the Waikato. Eastward of the lake the highest point of the plateau is attained near to the northern slope of the Kaimanawa mountains, whence it dips in a north-easterly course, in the direction of the Bay of Plenty. Over a large area, along the western shore of the lake, the table-land maintains a more equal elevation than near the eastern shore-line, until it reaches the head of the Waihora river, whence it inclines north-westerly, around the high mountains of Titiraupenga, until it gradually merges into the broad, low valley of the Upper Waipa.

It is as near as possible in the centre of this vast area of elevation, that the enormous sheet of water forming Lake Taupo is situated. The position of the lake is in lat. 38° 37' to 38° 58' S.; long. 175° 46' to 176° 5' E. Its mean altitude above the sea, by barometrical measurements, I ascertained to be 1175 feet. The margin, or shore-line, assumes a somewhat oval shape, with a broad bay on the western side. It is twenty-four miles long in a north-easterly and south-westerly direction, and fourteen miles broad from east to west, and with a superficial area of over 300 square miles. It possesses one small island, which is situated near to its south-eastern shore, and its coast is surrounded with beautiful bays and headlands, which in some instances rise many hundreds of feet above the white pumice shore. Although the waters of the lake are comparatively shallow around a greater part of the margin, there are places where it is of an enormous depth, especially near its centre in the direction of the western bay.

In describing the watershed of this wide region, I may point out that the area of the lake basin may be defined by those divisions of the country which give rise to the rivers, creeks, and other waters flowing into it, and which have their origin for the most part in the extensive mountain ranges scattered over various parts of the table-lands.

Although on the most recent maps of the colony only about eight rivers, namely, the Waitahanui, Hinemaiai, Tauranga, Waimarino, Upper Waikato, Waihaha, and Waihora, are represented as flowing into the lake, I found on the western shore, in addition to other smaller streams, the Kuramanga, Kuratao, Whareroa, Mangakara, Whanganui,[40] Waikino, and Waikomiko, besides three other streams on the northern shore, the names of which I was unable to obtain.

It will therefore be seen that there are not less than seventeen rivers running into this lake, with innumerable smaller streams, while it should be remarked that the only river or stream of any kind flowing out of this immense area of water is the Waikato, at the north-east end. Most of the rivers on the eastern side of the lake receive their waters from the north-western slope of the Kaimanawa mountains, and those from the west, from the Tuhua, Hauhungaroa and Hurakia ranges. Comparatively little water flows into the lake at the northern end, since the country thereabouts dips mostly in the direction of the valley of the Waikato. It is in fact at its southern end that the lake receives its greatest volume of water from the Upper Waikato river, and its numerous tributaries. This river, rising at an altitude of 7000 feet on the eastern side of Ruapehu, is fed by the snows of that mountain, and of Tongariro, as well as by the enormous watershed of a large portion of the Kaimanawa mountains, along the western base of which it runs in its winding course to the lake, receiving likewise on its way the eastern streams of the Kakaramea ranges, and the overflowing waters of Lake Rotoaira, as they descend by the Poutu river. With but one outlet to relieve it of this tremendous watershed, it is not surprising that the waters of the lake rise rapidly during the rainy season, while with the continuance of heavy winds its waves are lashed into fury, and break upon its shores with the force and roar of a raging sea.

In considering the geological features of the region of Lake Taupo, it may be imagined here, as in other cases, that the primary volcanic eruptions were submarine, and that when first that portion of New Zealand now known as the North Island appeared above the surrounding sea, forced upwards by some volcanic freak of nature, the Taupo table-land rose perhaps rapidly, perhaps by slow degrees, to its greatest elevation. The volcanic eruptions which produced this phenomenon may, in short, have been instantaneous or slow in their action; but be that as it may, their work has been indelibly impressed upon the face of Nature in a way which has caused its wonderful results to last through vast periods of time. The volcanic agencies, however, did not rest here. The Plutonic fires, still active in the interior of the earth, burst through the elevated plane, and caused big mountains to rise up in the form of serrated ridges and truncated cones, which poured out their streams of lava and other kindred products over the surrounding country. Hence dotted along the Taupo volcanic zone are stupendous mountain ranges and graceful trachytic cones standing alone or rising from amidst a cluster of minor elevations to heights which vary from 1200 to nearly 10,000 feet above the level of the sea. Of the former class the most extensive are the Kaimanawa mountains and the kindred systems, with the Tuhua ranges and the wooded heights of Hauhungaroa and Hurakia, while the cone formation is exemplified in the grandest proportions in Ruapehu, Tongariro, Pihanga, Tauhara, Kakaramea, Kuharua, Puke kai-kiore, Karangahape, Haurungatahi, Hikurangi, Hurakia, and Titiraupenga, all of which indicate various centres of volcanic action.

The existence of a body of water of the area of Lake Taupo, and of its form and depth in the centre of this elevated region, may be accounted for in several ways. It may have originated in the terrific throes of an earthquake, or by a fracture or break in the plateau. I am, however, of opinion that the present basin of the lake was at one time an active crater, which had its existence long prior to the period when the volcanic cones surrounding it sprang into existence, and that at the time of its activity it was considerably higher than it is at the present day, its subsidence or depression having been caused by one of those sudden changes peculiar to regions subject to volcanic disturbance. Moreover, many of the leading geological phenomena, as exemplified throughout the surrounding country, would seem to point to this conclusion. Perhaps one of the most remarkable features of the Taupo volcanic zone at the present day is its vast pumice plains, which radiate, as it were, from a common centre over an extensive area of country. The largest of these plains stretches in a north-easterly direction from the lake shore, with a gradual fall or incline in the same direction. It is through the western margin of this plain that the Waikato winds through its terraced valley, and it is around this valley that may be more distinctly seen the enormous deposits of pumice, which have been distributed far and wide, as it were, by the action of rapidly rolling waters.

From every outward indication it would appear that this vast deposit of pumice rock had its origin in the once active crater forming the basin of the great lake, and that both Ruapehu and Tongariro rose above their still higher planes long after the period when the great Taupo crater now forming the cup of the lake was the principal outlet of volcanic fires in this wide field of Plutonic action. As a matter of fact the distribution of pumice drift around the enormous base of Ruapehu and Tongariro is as nothing when compared with the great pumice formation of North-Eastern Taupo, and this statement will apply equally to the plains westward and south-westward of the lake. The greatest overflow or distribution of pumice appears to have been, as before pointed out, at the north-eastern division of the lake basin, where the area of depression is greater than at any other part, and at a point over thirty miles distant from either Tongariro or Ruapehu. It was, I believe, when the fires of the great lake volcano died out that the waters rose from the subterranean springs below, and overflowing the then more elevated crater, distributed the light pumice rock over the area of country which had a gradual fall then as now in the direction in which the extensive deposits of pumice are still to be found. This enormous crater was, no doubt, at one time the highest point of the island, until its period of volcanic extinction and subsidence set in, after which stage the pent-up fires burst forth in the stupendous form of Ruapehu, and when the latter in its turn became extinct, Tongariro, with its minor system of volcanic cones, sprang into existence.

TERRACE FORMATION

TERRACE FORMATION AND HOT SPRINGS.
(Valley of the Waikato.)

I am not aware whether this theory of the crater basin of Lake Taupo is a new or an old one, and I only endeavour to exemplify it as it presented itself to my mind, after a careful examination of the country for many miles around the lake, and from data gained during my ascent of the highest mountains of this great volcanic centre. I may, however, likewise point out that the Taupo natives still have a well authenticated tradition, which would seem to show that even during the history of the race upon the island, the lake basin was at one period considerably higher than it is at the present day. But, beyond the above fact to support this theory, it is well known that the formation of lakes in extinct craters is common throughout the volcanic regions of the island. Lake Takapuna, near Auckland, may be taken as a notable instance. The blue lake at Wairakei, near Lake Taupo, is situated in a depressed crater, and Rotokawa, a little further to the east, is of the same formation. Lake Rotoaira, south of Taupo lake, is nothing more than a depressed crater, while there are no less than four lakes on the Tongariro mountains formed in the same way. There is likewise a lake formed by a crater on the summit of Ruapehu, while the two lakes which I discovered to the south-west of that mountain, and named respectively Rangitauaiti and Rangitauanui, were nothing more than depressed craters filled with water from subterranean springs.

When treating of the many wonderful natural phenomena presented by the Taupo volcanic zone, it may not prove uninteresting to refer, if only in brief terms, to the several centres of thermal action within the immediate region of the lake. Both at its northern and southern end considerable areas of country are covered with geysers, solfataras, fumaroles, and hot springs. At a short distance below the point where the Waikato leaves the lake, the banks of the river are studded with boiling springs and fumaroles in a very active condition, while not far from its eastern margin is situated a large geyser which is constantly throwing up boiling water and emitting vast volumes of steam. At Wairakei, still further down the valley of the Waikato, these wonderful phenomena cover nearly 4000 acres of country, and take the form, as before shown, of enormous intermittent geysers, steam-holes, fumaroles, solfataras, and hot mineral springs of the most varied order; while to the north-east of Lake Taupo, Lake Rotokawa forms the centre of a wide circle of hot springs and fumaroles. On the south side of Lake Taupo, the mineral springs and geysers of Tokanu spread over a wide surface, and on the northern slope of Tongariro are some of the largest and most active boiling springs in the country, while the crater of the great mountain itself is the seat of a tremendous thermal action.