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The Pamphlet Collection of Sir Robert Stout: Volume 67

Appendix No. 2. — Ascent Of Ruapehu: Extract from Mr. L. Cussen's Report, Dated June, 1886

page 78

Appendix No. 2.

Ascent Of Ruapehu: Extract from Mr. L. Cussen's Report, Dated June, 1886.

In my monthly report for April I informed you that on ascending Ruapehu in the early part of that month we found a crateral hollow on its summit containing warm, or probably boiling, water: as this matter may be of interest at the present time, it may be well to give a few details and a short description of the mountain, so far as I can from the few notes which I was able to make in the limited time I could devote to the subject, my object, of course, being to complete the trigonometrical observations at the trig, stations in time to descend to our camp before night. We ascended the mountain from the western side, following a long and tolerably regular ridge which runs down from the top of the cone to its base. The ascent was not very difficult: we accomplished it in four and a half hours from our camping-ground, which was situated 5,000ft. above the sea-level; we had therefore 4,000ft. to ascend, nearly 3,000ft. of which was over frozen snow. As we ascended, on all sides of us were examples most various and instructive of volcanic phenomena, and the forms and shapes assumed by lava in cooling. The most remarkable feature of the mountain is the crater-lake on its summit. This lake is situated at the bottom of a funnel-shaped crater, its steep sides being mantled with snow and ice. I had no time for measurements to ascertain the correct dimensions of the lake, and its peculiar surroundings made it difficult to estimate them with any degree of accuracy. The water seemed to me to occupy a circular basin about 500ft. in diameter; it is situated inside the two peaks, Paritetaitonga and Ruapehu, which are about 60 chains apart on the southern portions of the mountain; the lake would be about 300ft. below the peaks, and quite inaccessible, except with the aid of a long rope, and even then the descent over the icy masses would be attended with danger and difficulty. On first reaching the top of the peak I noticed small clouds of steam floating over the surface of the lake; on watching it more closely the water appeared now and then to assume a rotary movement; eddies and whirlpools seem to pass through it from the centre to the sides, steam or vapour flashing up from the eddies.

It was impossible to discover the exact form and construction of the summit of Ruapehu, the whole mountain-top being covered with a deep mantle of snow, which completely fills up and hides all the hollows between the peaks. Three prominent peaks are presented to page break
Hydrographic Survey of Lake Taupo

Hydrographic Survey of Lake Taupo

page 79 view: Paritetaitonga, on which our station stands, is on the southwestern end of the mountain; to the south-east of it, about 60 chains distant, is Ruapehu, which is the highest point of the mountain; exactly a mile to the northward of Paritetaitonga is the third peak, called To Heuheu, not quite so high as Paritetaitonga. All between these three points, with the exception of the crateral lake, is a great undulating snow-field, intersected by irregular crevices of immense depth. From the vertical inward faces of the three peaks, their more gradual outside slopes, and the general configuration of the mountain on the western side, it would seem that the peaks formed part of a circular crateral ring, the diameter of which would be about one mile, and the western portion of the lips of which have been destroyed. The crater in which the hot water now exists would probably have been formed, with others, on the floor of the old truncated cone. As stated in my monthly report for April, I noticed on several days after our ascent of Ruapehu a column of steam rising out of the crater and ascending high above the mountain-top. I drew the attention of Te Heuheu and several of the oldest Natives in the district to this fact, and they all agreed that it was quite a new thing—they had never heard of steam arising from Ruapehu before. I think it is more than probable, however, that a low state of volcanic heat prevailed in the crater throughout. Five years ago, when triangulating on the Kaimanawa ranges, I noticed a column of vapour arising from Ruapehu in the position of the crater; but, not knowing of: the existence of the lake, I thought it must be a cloud or fog arising out of one of the gorges of the mountain, although it seemed very like a column of steam.

When observing angles at Paritetaitonga, although the stones which formed the station-mound were frozen hard together, my instrument would not remain level; the same thing occurred at Hauhungatahi station, eight miles to the westward of Ruapehu, which was likewise frozen hard when I was observing there. Three years ago, when taking angles on Ngauruhoe, I found the same difficulty in keeping my instrument level, although the ground on which it stood was formed of a solid conglomerate mass.*

* Mr. A. D. Wilson, writing on the 20th July, reports the same trouble. He says: "I experienced great difficulty in keeping my instrument level when observing at Hauhungatahi, even though the ground was ironbound with frost. I ascribe this less to present volcanic action than to the place where the trig, is being an old crater, which having been filled up with very loose materials never properly consolidated, the slightest weight upon the surface is sufficient to depress it. I am led to assume this from the character of the stuff taken out when digging the hole of the tube, which looked as if it had first been burnt and then put through a crushing-machine."