(through many centuries) extreme variations of temperature, the period during which such effects were produced must have widely exceeded in duration the 'glacial period' of Europe. If moraines were built from matter excavated by glaciers, the moraines of Greenland should be the greatest in the world!
The absence of moraines upon and at the termination of this great Mer de Glace is due to the want of rocks rising above the ice.[1] On two occasions, in 1867, I saw, at a glance, at least 600 square miles of it, from the summits of small mountains on its outskirts. Not a single peak or ridge was to be seen rising above, nor a single rock reposing upon the ice. The country was completely covered up by glacier; all was ice, as far as the eye could see.[2]
There is evidence, then, that considerable areas of exposed rock surface are essential to the production of large moraines, and that glacial periods do not necessarily produce vast moraines. That moraines are not built up of matter which is excavated by glaciers, but simply illustrate the powers of glaciers for transportation and arrangement.[3]
- ↑ I refer to those portions of it which I have seen in the neighbourhood of Disco Bay. There are moraines in this district, but they were formed when the great Mer de Glace stretched nearer to the sea,—when it sent arms down through the valleys in the belt of land which now intervenes between sea and glacier.
- ↑ The interior of Greenland appears to be absolutely covered by glacier between 68° 30'—70° N. Lat. Others speak of peaks peeping through the ice to the N. and S. of this district; but I suspect that these peaks are upon the outskirts of the great Mer de Glace.
- ↑ The striations which are found upon rocks over which glaciers have worked, are universally held by the ablest writers to be caused by foreign matter held in the grip of the ice, or rolling between it and the rock -bed (§ 9, p. 146). If the principal source of the tools which make these marks is cut off, the marks should, of course, be less numerous.
The rarity of striations in the neighbourhood of the great Mer de Glace of Greenland was very noticeable. There was perfection of glaciation; but, over large areas, striations, flutings, and groovings were entirely wanting. Weathering, subsequently to the retreat of the ice, had not taken place, to any perceptible extent, in the localities to which I refer.
Striations, groovings, and flutings, are seen on the outskirt land; but they are less common in Greenland than in the Alps.
