MORAINES
There is a remarkable feature of the glaciers of this country which stamps them as unique in one respect—I refer to the very extensive moraines. I write feelingly of this, for my acquaintance with them has been a very close one, and they have impressed me very deeply—in more ways than one.
The large glaciers of which I have written in this work are completely moraine-covered over their lower parts.
‘SURFACE’ MORAINES
Moraines may be divided into four sections: ‘Lateral’ moraines, fringing the sides of the glaciers, their outlying portions often being ‘dead’—that is, at present unmoved by the action of the ice, and forming banks, as it were, for the ice stream to flow between; ‘medial’ moraines, which begin at the junction of two streams of ice and often continue for many miles to the terminal face; ‘terminal’ moraines, formed by the depositing of detritus at the melting point or end of the glacier; and, lastly, ‘surface’ moraines (so called by Professor Hutton of Christchurch, N.Z.), which are the combined accumulations of the first two divisions in the lower parts of the glacier.
It is these ‘surface’ moraines that are such a characteristic feature of the glaciers situate on the eastern side of the chain in New Zealand. Of those on the western side I am not able to speak with authority, never having visited them myself; but I understand that they do not carry such a large quantity of detritus as those of the eastern slopes.
This disparity remains to be accounted for and awaits an explanation. I have a theory of my own upon the subject, which, however, as yet I would not like to put too strongly forward.
On both sides of Mount Cook, on Mount De la Bêche (ten miles further along the chain), and on a peak just north of the Hochstetter Dome (ten miles still further north) I have observed enormous exposed sections of the rock strata, which in each case dip at a steep angle from east to west, presenting slab faces, not easily disturbed by the action of the frost, to the westward, but broken and fast denuding faces (‘basset’ faces, as they are geologically termed) to the eastward. I am hoping at some future time to further investigate this interesting subject.
As the western glaciers, however, must descend steeper valleys than the eastern, I make no doubt that their rate of progress will be eventually ascertained to be greater than that of the latter, and this would militate largely against an accumulation of moraine upon the ice.
THE SURFACE OF A GLACIER