Notes on the Franz Josef Glacier, February, 1934
[Read before the Philosophical Institute of Canterbury, 4th April, 1934; received by Editor, 13th April, 1934; issued separately, March, 1935.]
In 1910 Dr. J. M. Bell gave in his Geographical Report on the Franz Josef Glacier an accurate record of the position of the terminal face as it appeared in the years 1908 and 1909. Also Mr R. P. Greville, a surveyor on Dr. Bell's staff, selected certain points near the terminal face of the glacier as it stood in 1909, and drove strong iron pegs into the rock to mark its position. All records made subsequent to their placement naturally use these as convenient points for reference.
The present author has visited the glacier on various occasions, and made observations on the face, the results being published in the Transactions of the N.Z. Institute in 1914 and 1921, the former based on observations taken by Mr Alec Graham.
In 1893–4 Messrs Douglas and Harper noted the position of the face and left cairns to mark it, and Mr Harper in Volume III of the N.Z. Alpine Journal (December, 1926) gives a map showing its position as it stood in 1894, as well as the approximate line in 1926. I should remark, however, that there is a rock near the north-west front fully visible in 1921 and in 1934 which is not shown on the map, although it should have been clearly visible in 1926. By the kindness of the Chief Surveyor for Westland, I have by me a tracing of Douglas's map made in 1898, with a record of the line as it appeared in 1894.
In the following table I have recorded as far as I can the distances of the face from Bell's pegs, as measured in 1909, 1912, 1914, 1921, and 1934, the last measurements being made by myself during a visit in February of this year. Included are also Douglas's obtained from his 1898 map and Harper's own obtained by making measurements on his 1926 map. Records are given in metres, with a plus sign if the ice is in front of the peg, and a minus sign if it has retreated behind it.
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|From Peg.||Douglas and Harper.||Bell and Greville.||Alec||Graham.||Speight.||Harper||Speight.|
(i)These results are obtained by measurements of Douglas's map of 1898.
(ii)Bell and Greville also located the terminal face in 1908, and a comparison shows that by 1909 it had advanced slightly at nearly every point on the line.
(iii)The figures in these columns were obtained by the kindness of Mr Alec Graham, and were recorded by myself in 1914.
A conspectus of these results indicates that the glacier probably reached a maximum in 1893–4, although at some points it was further forward in 1909, and it must be remembered that a photograph taken in 1867, and examined by Mr Harper, indicated that it was then from 80 to 100 yards further forward still (Pioneer Work in the Alps of New Zealand, 1896, p. 306). The records of 1912, 1914, and 1921 show retreat almost all along the line. In 1926 there was a probable advance, and in 1934 the front as a whole was further down the valley than in 1926. The large numbers assigned generally to the distances of Pegs Nos. 1 and 7, which are placed on the bounding walls of the glacier, are due to the outlet of the river being at the side where the large figures are recorded, or due to the river having but recently left that side.
In order to furnish some idea of the present position of the terminal face, the state in front of each peg will be taken in turn, and as the site of these pegs is somewhat difficult to determine at present owing to the growth of scrub, etc., some note will be made of their true location so that subsequent observers may be able to find them readily.
No. 1.—This is close to the end of the formed track to the glacier, but just covered up at present by “riverbed” moraine.
The glacier is back at this point, and abuts against the valley side 280 metres away from the approximate position of this peg. The side of the glacier is for the greater part of the distance about 60 metres from the valley wall. The bearing of the face is first 347°, and then it changes to 26° and continues to the side of Wilson Rock, over which moraine is being pushed so that the plants established on it since 1921 are being destroyed. Only a small part of the solid rock, viz., that at its N.W. corner, is now visible under the mask of moraine and the ice behind it. The ice front at this spot is oriented N.E.-S.W.
It may be appropriate to mention here that the material on the front of the glacier is rounded river gravel, almost entirely of schist, and not true moraine, which is of greywacke with an occasional fragment of slate. The “river-bed” moraine is pushed before the advancing ice and raised at the same time, so that it covers the front of the glacier to a breadth of from 20 to 40 metres, forming a belt parallel to the ice-front. The moraine covering Peg No. 1 is of this material.
No. 2.—This is on the western end of Harper Rock, but from the form of the present terminal face it was of little value for the purpose of measurement. It might be noted that in 1893–4 the ice a little to the west of the peg was slightly further forward than the peg itself.
No. 3.—This is on the top of Harper Rock, near the edge of the southern cliff face, and almost at the corner of the rock. There have been recent heavy falls from the face just below it, and if they continue the peg will soon be displaced.
From the peg, the face of the glacier covered with debris is distant 71 metres on a bearing of 188°. Just west of this point lies Wilson Rock, which was uncovered at my last visit. The ice is pushing river-bed moraine over this, and destroying the plants and shrubs which had become established. At the present time only a few square yards of solid rock show under this cover, and from the general evidence it promises to be completely covered at an early date.
To the east of this the face of the ice is slightly retired, while opposite the end of the unnamed rock to the east of Harper Rock, now known as Teichelmann Rock, there is a pool of water from which a small stream discharges. The ice is now 16 metres from the eastern end of this rock on a S.S.W. bearing.
No. 4.—This is on Park Rock, on the high point immediately overlooking the low ground in the direction of Strauchon Rock. The form of the rock is different from that shown on Bell's map, since to the north it was then partly covered by ice, which crowded over a lower shelf now exposed.
To the south of the peg and distant 53 metres from it, ice occurs covered with debris, most of which is schist and of river-bed origin. This has been pushed forward in front of the ice for nearly 20 metres, and has been shaped into ridges, some of which are overriding the vegetation growing on the rock and on its old covering of debris. At this point the ice is level with the summit of the rock, though distant from it, and it is covered with a thin veneer of true moraine consisting of greywacke and occasional slate.
Apart from the gullies worn on the margins of the glacier, the ice at this point is farther back than at any other point in the face, and it seems to have retreated since Harper made his observations in 1926.
No. 5.—This is near the south end of Strauchon Rock and about 10 metres above the river-bed.
The face of this glacier is about 128 metres from this peg. It is fringed with moraine, and has its front covered with river-bed material. The ice at this point shows an overthrusting of the upper layers, the angles of the thrust planes being usually about 15° from the horizontal, but at times they are greater and again lower. In this part the ice comes forward to just beyond the line between Pegs 4 and 7.
No. 6.—This is about 4 metres above the river-bed on Barron Rock. Between it and the terminal face lies the main stream of the Waiho. In the direction of Peg 7 lies Outlet Rock. This is in a slightly different position from that recorded in Harper's paper. It is said to have been uncovered for 10 yards when seen originally. The rock itself is 20 metres long and 12 wide, with an extension to the south under the river-bed of 20 metres, where another small outcrop shows.
No. 7.—This is on the eastern front of the glacier about 60 metres above the river on a rock generally known as the Gallery Rock, from the gallery which once passed round it and was destroyed in the 1908 advance at this part of the front.
As the main stream issues from a cave on this side of the glacier, the terminal face is distant 262 metres from the peg. Further up the glacier at Roberts Point the ice is crowding over the solid rock, and below this point, at Rope Creek, there is a fringe of bare rock at the side, and even this at present shows signs of being overridden, while lower down still, near the outflow of the river, the ice is right against the rock wall.
A general survey of the whole face shows that it is further forward than it was in 1921, and apart from the eastern margin and Park Rock it is further forward than it was when Harper observed it in 1926. The record of 1921 was obtained when it was near the minimum position. This was noted then as probably being the case, since there was evidence of an advancing wave of ice further up the glacier, as is the case at the present time, for ice is now crowding over Roberts Point on the east and over Cape Defiance on the west side of the glacier.
I have photographs taken in 1927 and 1928, kindly lent by Mr G. E. Mannering, also photographs taken in 1929, kindly lent by Mr J. Mitchell, all of which show that Wilson Rock was hardly as much covered as at present, for the vegetation growing on it shows more in these pictures than it does now. In 1929, however, the ice was much higher behind this rock, and the same holds good for Park Rock. Upstream from the latter the ice was further forward in 1928, whereas the 1929 picture shows a distinct advance north-east of the rock and that the shelf below the peg was then partly covered, whereas it is bare now. This implies a present slight recession at this point. Mr Peter Graham, of the Franz Josef Glacier Hotel, says that an advance set in about four years ago, but that there are always slight oscillations of the face during a general forward movement.
Before leaving consideration of this glacier, one or two features apart from the condition of the face may be referred to. The first concerns the presence of the line of rocks, such as Sentinel Rock, Harper Rock, Park Rock, etc., which form such upstanding objects in the floor of the valley below the ice. They are certainly roches moutonnées, but the face against which the glacier impinged shows very few of the characters which belong to the scour side of such rocks, though they are certainly striated. The upstream faces of Sentinel Rock, Harper Rock, Teichelmann Rock, Park Rock, and the steep rock face where the gallery was once situated are in rough alignment on a bearing of 130°, and there is a crush belt to the south of the Gallery Rock at a slight angle from the same line and extending up the eastern wall of the main valley. Faulting, with an upthrow to the north, will explain the latter feature, and, incidentally, that of the upstanding rocks in the floor of the valley. Also the general absence of abrasion on these rocks, and specially on the southern face of Gallery Rock, indicates that they had not been subjected to glaciation for an extended period as upstanding rocks, and certainly had not, in such a form, experienced the glaciation at its maximum. Therefore faulting probably took place after the glacial period had commenced and before it had ended. This contention is supported by the recession of the glaciated walls of the valley above Gallery Rock as compared with the walls at the rock and further down the valley. One would have expected the surfaces to be continuous, and it is not so. It is possible, too, that other breaks in the valley walls, higher up, may be due to a similar cause, and the ice falls below Roberts Point may be attributed to the ice over-riding a barrier due to upfaulting to the north.
Another point illustrated by these glaciated valley walls is the supposed indication of a former level of the ice as deduced from the change in the nature of the vegetation up the mountain side above the ice. There is a lower belt where the trees are stunted, and an upper belt where they are larger, and it is usually assumed that the difference is due to the more recent abandonment of the lower levels by the ice. Mr J. Mitchell, one of the guides at the glacier and a keen observer of natural history, has mentioned to me that the large trees correspond to a belt of crushed rock, probably due to the over-thrusting of the schist by the greywacke, the movement being from the east, and that the difference in growth of the trees may be due to the difference in the nature of the ground on which the trees have been established, the lower part being solid inhospitable schist, and the top the more kindly broken greywacke. If the divergence in the character of the vegetation is really due to delayed evacuation of the lower levels by the ice as compared with the upper levels, then the lower belt of stunted trees extending along the valley walls should rise as steeply as the valley gradient, if not more steeply, and it does not do so. This is in favour of Mr Mitchell's contention, but the point needs further investigation.
Advantage was taken of this last visit to the Franz Josef to make an examination of the terminal face of the Fox Glacier, which lies in a sub-parallel valley 15 miles to the west. I had not see
this glacier since 1905, when the terminal face was so indefinite that one could hardly tell where the river-bed ended and the moraine-covered ice began. At the present time the glacier has moved forward and shows features similar to those of the Franz Josef. River-bed material has been lifted up and pushed forward along its front, and in one case the ice has lifted this material with the trees on it still growing in position. The forward movement of the ice is indicated also by the movement of the upper layers over the lower layers along thrust planes. Behind the belt of river-bed moraine lies the true moraine, formed chiefly of angular greywacke rocks like those of the Franz Josef, but there is more of this in the case of the Fox, since a large fall occurred about three years ago from the end of Passchendaele Ridge, about two miles up the glacier, and this has made its appearance at the terminal face. There is another considerable fall of rock lower down the glacier on the eastern side. The greywacke forms a capping on the schist, and readily breaks away when the latter rock fails.
The stream issuing from the glacier lies almost entirely on the western side, and it comes from a large cave as a full-bodied river close to the margin of Cone Rock, a picturesque ice-scoured mass occupying a sub-central position in the valley, although at the present time no ice flows on its western side. The stream issues just opposite one of the cairns placed by the late Charles Douglas. I have been enabled to locate this through the kindness of the Chief Surveyor for Westland, who supplied me with a tracing of one of Douglas's maps filed in the office of the Lands and Survey Department. “On April 25th, 1894, at a bearing of 355 mag., the ice was 37 yards distant” (A. P. Harper, loc. cit., p. 330). From the vantage point furnished by this cairn the following sequence can be seen in the western edge of the ice:—
1. Moraine, covered in places with vegetation and lifted by ice, with one or two ridges of moraine pushed forward or carried forward by the ice.
2. Main ice of the glacier, as exposed at the actual outlet of the river, a section through this from the top showing the following:—
(iv) Moraine, composed of angular greywacke fragments.
(ii) Wedge of moraine, over which ice is being pushed.
Here follows the river, and the ice (i) is apparently the same as that marked 1 above, though there may be other layers pushed forward between this and the terminal face further downstream in the middle of the valley, obscured by the coating of river-bed moraine. This suggests that sometimes a section in an old glacier deposit may be delusive, when moraine rests on gravel, and this in turn rests on tillite. It may not indicate two periods of advance with an intervening retreat, since the whole section may belong to the same phase.
Judging from the map kindly furnished me by the Lands Department, the present position of the terminal face is not as far advanced by about 100 metres as compared with its position as observed by Douglas in 1893–4. However, in front of the present face, nearly up to Douglas's recorded position, there are sink holes, one over 20 metres in diameter and 3 metres deep, which indicate that the ice has recently been under the river-bed or is actually under it now about 50 metres further down the valley. The whole attitude of the present terminal indicates that the glacier is at present advancing, though behind the face there are holes of considerable size, with streams issuing from them and running under the ice, which may herald an impending retreat.
A comparison of the records of the two glaciers suggests that the advance as well as the retreat is contemporaneous, seeing that Douglas's record of 1894 shows that both were well advanced. There is, however, the old photograph of the terminal face of the Franz Josef taken in 1867, which, according to Harper (loc. cit., p. 306), shows the terminal face from 80–100 yards further down the valley than it was in 1894, so that even in 1894 it may have been actually retreating. There are no data from the Fox to show any correspondence on the part of this glacier with the advance in 1908–9. At the present time the condition of the face in both cases is similar, but the Franz Josef probably will advance in the near future, whereas the condition of the Fox implies retreat. Much more detailed observation is necessary before correspondence in behaviour can be definitely established or disproved.
Note.—During the year 1932 Mr H. L. Hume, B.E., of the Public Works Department made a number of observationss on the rate of flow of the Fox Glacier, and he has kindly placed them at my disposal. They are reproduced as follows:—
Analysis of Observations of the Flow of the Fox Glacier, South West-Land, New Zealand, Along a line approximately 60 chains (1200 Metres) From The Terminal Face in 1932.
|Number of Station.||Distance of Station from edge of bank.||Period of Observation, 1932.||No. of days.||Total movement for period.||Average movement per day for each period.||Average movement per day over 57 days.|
|1||65.6 m.||9th Oct. to 30th Oct.||21||4.03||.21||.19|
|30th Oct. to 6th Dec.||36||6.62||.18|
|2||119.5 m.||9th Oct. to 30th Oct.||21||6.34||.30||.27|
|30th Oct. to 6th Dec.||36||8.90||.25|
|3||196 m.||9th Oct. to 30th Oct.||21||9.30||.44||.375|
|30th Oct. to 6th Dec.||36||12.04||.34|
|4||248.4 m.||9th Oct. to 30th Oct.||21||10.21||.488||.49|
|30th Oct. to 6th Dec.||36||18.11||.50|
|5||296.3 m.||9th Oct. to 30th Oct.||21||11.28||.537||.54|
|30th Oct. to 6th Dec.||36||19.51||.543|
This result indicates a somewhat low rate of speed, but it is possible that it may be explained by the line of stations being taken across a somewhat flat reach of the glacier. Mr Hume has kindly offered to continue his observations and also to keep records of the position of the terminal face, and other features of interest in connection with the Fox Glacier.
Terminal face of the Fox Glacrer taken from Cairn B on Cone Rock According to Douglas and Harpen the ice was only 37 feet away from thus spot in 1893–4 Ice reaches right down to the point in the river, for at that place it lies under debris with growing shrubs, and the river washes an actual ice face Most of the debris showing is true moraine, but there is an admixture of river-bed material, and in some places this is inter-stratified with the ice