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The Pamphlet Collection of Sir Robert Stout: Volume 67

Lake Taupo

page 80

Lake Taupo.

In the month of January last I took a series of soundings of Taupo Lake, the details of which are shown on the map accompanying my report. The lake covers an area of 154,680 acres; its greatest length, from Tapuaeharuru to Waihi, is 24 miles 70 chains; its greatest width, from Waihaha Bay to the mouth of the Hinemaiai River, is sixteen miles and a half. The result of the soundings shows that the lake has an almost level bed, the average depth being 65 fathoms, and the greatest depth, at a point nearly in the centre, being 89 fathoms. Only in one place was shallow water found at any considerable distance from the shore: this point is the reef about three miles to the north of the Motutaiko Island, where the rock is covered by only 7ft. of water.

Motutaiko Island is one of the most interesting features of Lake Taupo. It is formed of a column of rhyolitic lava, ascending perpendicularly from the bottom of the lake to a height of 600ft., half of it being below the water, and the upper half covered with stunted timber and scrub. Its construction points to the probability that it is the neck of lava which filled an old volcanic vent, and it was probably surrounded by a cone of loose ejecta, which have been worn away by denudation, and now cover the floor of the lake. To the north-east of Motutaiko Island, and extending northwards from near the mouth of the Hinemaiai River along the shore for a distance of three miles, is a ledge running about two miles out into the lake; this ledge is covered by only from two to three fathoms of water, and at its edge the depth suddenly increases to over 30 fathoms. All along this ledge are lying large totara snags, many of them protruding above the water, and they seem to be in a good state of preservation. The Maoris have no knowledge as to how they came there, nor have they any tradition of a change taking place in the formation of the shore: it is more than probable that they were deposited by a slip occurring on the high land of the shore, at a time when the surface was covered with forest. A landslip on such a scale would scarcely have happened since the Natives have inhabited the district without their retaining some account of it, and it therefore seems probable that the timber has been lying there for four hundred years or more.

The evil spirit, or taniwha, of Taupo Lake, called Horomatangi, is said by the Natives to inhabit a cave in the reef which lies to the north-east of Motutaiko Island. They say that when a canoe approached the reef, Horomatangi lashed the water into foam, throwing up pumice and stones, and creating such a disturbance that the page 81 canoes were frequently capsized. Another interesting legend in connection with the reef was told to me by Te Heuheu. He said that a totara log possessing great mana or power floated in the neighbourhood; sometimes it lay near Horomatangi reef, and sometimes it appeared with its end resting on the shore of the lake. It had worn for itself a passage through the snags from the shore to the reef; it would lie for days touching the shore, and then suddenly depart, and travel through the clear passage to Horomatangi, a distance of nearly two miles. An elderly Native assured me that, when a young man, in a journey from Tapuaeharuru to Motutere, he had sat on the log to rest as it lay on the shore of the lake; on returning in a day or two after he saw it floating far out on the lake on its way to Horomatangi. When the mission church was built at Motutere, the missionaries induced the Natives to use the log in the building of the church: the Native who dragged it out of the water died soon after, and all those who assisted in carrying it to the site of the church, or preparing it for the building, also died within a short time after. The movements of this log—which, no doubt, were considerably exaggerated—may be due to the current of the Hinemaiai Stream, which passes slowly through the lake, being deflected in the direction of Horomatangi's reef by the ledge on which the submerged timber lies; the log would thus be carried out by the current, which extends to the reef, where it might remain till a westerly or a north-westerly wind drove it back against the light current of the river, until it again reached its former position on the shore.

At Karaka Point, a promontory four miles south of Tapuaeharuru, are some interesting caves. They were worn by the action of the water on the volcanic conglomerate in which they are formed. The caves are about 30ft. above the present level of the lake. Underneath the tufa of the caves, and along the shore of the lake, the rocks are rhyolitic lava. Three miles to the north-west of Karaka Point, on the shore of the lake, a large deposit of iron-pyrites appears in the rhyolite and tufa beds.

With the exception of the sandy bays of Whangamata, Waihora, Waihaha, and the several smaller bays shown on the map, the whole of the northern and western shores are formed of steep rugged cliffs of rhyolite, intermingled with which are masses of tufa and volcanic ashes. The heights of these cliffs vary from 100ft. to 800ft. above the lake, with generally deep water close alongside them—from 40 to 50 fathoms being found with our boat made fast against the rocks. The scenery all round the western arm is picturesque and beautiful: there are numerous interesting waterfalls and many secure page 82 and picturesque boat-harbours, with a depth of water from 10 to 40 fathoms within them; and safe anchorages can he reached, with good shelter from almost every wind.

The western shores of the lake are in many places wooded to the water's edge, the trees frequently seeming to grow on the almost hare rocks, which protrude here and there through the foliage. The Natives have their settlements inside the little sandy hays, and on the alluvial flats along the several rivers which empty into the lake.

Karangahape Point, with the little island-rock of Motuwhara, which lies a short distance off the point, would afford an interesting subject for the study of a geologist. The cliff is 1,500ft. in height from its base at the bottom of the lake to its summit. As will he seen from the section, it rises quite perpendicularly from the floor of the lake: a portion of it, 600ft. above the water, overhung our boat, whilst the lead-line, dropped close alongside the cliff, showed a depth of 400ft. The formation round the point is alternate bods of rhyolitic lava, scoreous tufa, and ashes. The little island of Motuwhara was probably a crater-plug: it is composed of rhyolite. At one time it was an important pa of the Ngatituwharetoas, and a safe retreat from their enemies in time of war. At Karangahape Point are to be seen Tamatea's two dogs, which he left there to guard the point: they are represented by large masses of consolidated tufa, some 30ft. in height. It would be difficult to trace in their shapes any resemblance to the form of a clog. Many of the Natives to the present day retain a superstitious awe of these stone dogs, and I have seen them cover their faces in passing by them, as to see Tamatea's dogs would probably cause a storm and the wreck of their canoe.

It is unnecessary for me to enter upon any description of Tokaano, its thermal springs and other natural curiosities, which are all pretty well known. I may mention, however, that there are a number of hot springs and fumaroles on Kakaramea Mountain which I believe have not hitherto been known to Europeans. They are situated in the forest, at the head of the Waihi Stream, and about three-quarters of a mile north of the highest point of Kakaramea. They occupy a considerable area, extending for about 20 chains along the stream. The principal one is over 100ft. in length, and about 30ft. in width; the water is muddy, of a greyish-cream colour. Fumaroles, steam-jets, and small mud-volcanoes abound. Several of the springs are of a boiling heat.

A distinctly-marked terrace extends right around Taupo Lake, 100ft. above the present water-level. This terrace plainly indicates that the water stood for a long period 100ft. higher than it now is: page 83 the subsidence is probably due to the lowering of its only outlet, the Waikato River, where it probably broke through a barrier, about one mile from the point where it leaves the lake. Te Heuheu points out a flat rock at the edge of the lake at Waihi, which, he says, his ancestors used for a sacrificial altar shortly after their first arrival in Taupo. This would show that the lake has not altered its level within the last four hundred years, and from the appearance of the shores it is probably a much greater length of time since the subsidence took place.

It has been suggested that a great deal more water flowed into Taupo Lake from the many rivers which discharge into it than goes through its only outlet, the Waikato River, and that probably the volcanic foci in the district might be fed by the lake. To any one who has seen the volumes of the many rivers which flow into Taupo Lake it certainly would appear strange that the seemingly small outlet of the Waikato River Would carry off as much water as is supplied by the infalling rivers. Whilst traversing the shores of the lake I took the opportunity to measure the volume of its rivers and streams. This was very carefully done, and under favourable circumstances, in fine weather, no rain having fallen during the operations. The Waikato River was measured where it leaves the lake at three different periods of the operations—namely, at the start; when half the rivers had been gauged; and at the end: the results showed that practically the same quantity of water was discharged as flowed into the lake: the actual quantities being: inflow, 16,455 gallons; outflow, 16,484 gallons per second.

I am indebted to Major Scannell for the following interesting narrative of the sudden rise and fall of the water at the north end of the lake on or about 28th August, 1883. On the day mentioned, a little schooner, which used to ply across the lake, was lying afloat at Tapuaeharuru. Some men working close by noticed that the schooner was suddenly left high and dry. They went to shove her afloat again, and in doing so they noticed that the river had fallen about 2ft. In the course of fifteen or twenty minutes it rose again to its previous level. This phenomenon was noticed by four or five people. It occurred at half-past twelve o'clock in the day. On that same afternoon, between one and two o'clock, Sergeant-Major Smith and Sergeant Miles, of the Armed Constabulary Force, were bathing in a warm spring called Waiariki, situated on the bank of the Waikato River, about a mile from the lake; the bath was fenced round with stones on the side next the river, and it stood about 2ft. above the level of the water. They found their bath become suddenly page 84 cold, and were astonished to find that the river had risen to a level with it. It remained so for about five minutes, and then suddenly resumed its former condition. So far as I have been able to learn, this was the only occasion on which the phenomenon occurred.*

The origin of Taupo Lake is an interesting physiographical question, and one to be dealt with by an abler and more experienced observer than myself: sufficient evidence has probably not yet been collected to lead to any definite conclusion on the subject. The jagged appearance of the volcanic rocks forming the steep northern and western shores leads at once to the conclusion that they were separated from the masses of which they originally formed part by some violent agency, either of eruption or subsidence. The islands and reefs in the lake are more than probably plugs of volcanic vents and lava-flows; and it would seem reasonable to infer that the lake owes its origin, firstly, to eruption, which was followed by a subsidence, and that subsequently some of the vents within it continued active as subaqueous volcanoes, the ejecta from which now form the comparatively level floor of the lake, having been worn away from the cones by denudation. I brought down some specimens of the rhyolitic lava from Taupo, and I am indebted to Professor Thomas for the classification of it.

Lawrence Cussen, District Surveyor.

By Authority: George Didsbury, Government Printer, Wellington.—1887.

* The Surveyor-General, in his "Annual Report on the Surveys of New Zealand, 1885-86," says, "The sudden rise and fall of the waters of Lake Taupo on the 28th August, 1883, referred to by Mr. Cussen, as noted by Major Scannell, and also recorded by Dr. Hector in Vol. XVI., Proceedings of the N.Z. Institute, page 536, is a striking testimony to the terrible force of the volcanic eruption of Krakatoa, Straits of Sunda, which occurred on the 27th August, about twenty-two hours before the wave of pulsation reached Taupo, a distance of about 5,000 miles. It is recorded that in the great earthquake of Lisbon in 1755, the waters of Loch Lomond and other lochs in Scotland rose and fell similarly—the distance in this case being about 1,300 miles. The great lakes in America were similarly affected by the Lisbon earthquake."