104 W. Gunn — Subaerial Denudation v. Glacial Erosion. 





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scars, we onglit to find ice-marks along their faces. 

 The presence of such ice-mark- 

 ings would not prove that the 

 scars were formed by glacial 

 erosion, but their absence tells 

 strongly against the theory. The 

 Shap granite of Wastdale Crag 

 being nearly exposed on all sides 

 may have had a larger quantity 

 of weathered and loose rock in 

 proportion to its area than many 

 other districts, and it seems to 

 have lain in the path of the ice- 

 sheet that went over Stainmore, 

 so it may have suffered greater 

 denudation. The old pre-glacial 

 alluvia and river-gravels of these 

 Dales must have all been swept 

 away, and haveh elped to swell consider- 

 ably the mass of glacial drift. They may 

 have been much more extensive than those 

 now existing (some of the present gravel 

 terraces are 70ft. to 80ft. above the river), 

 and may have rivalled in height above the 

 streams those of the Weald as described by 

 Messrs. Foster and Topley. 



Suppose we attempt to restore the pre- 

 glacial form of the ground in these valleys 

 according to Mr. Goodchild, in order to get 

 at the modus operandi of glacial erosion in 

 forming the scars and terraces. As there 

 were none of these, either of limestone or 

 sandstone (p. 362), each side of the valley 

 must have had a pretty regular slope some- 

 what like that of the light straight line A B m 

 the accompanying Figure (Fig. 2), and against 

 this surface the different beds of limestone {a), 

 sandstone (c), and shale (6), out-cropped. 



Now let us add the thick irregular terraced 

 line to represent approximately the present out- 

 line of the ground, and we are prepared to see 

 what rocks were removed by glacial erosion. It 

 must be understood that this is a generalized 

 section, certain sandstones in the shales which 

 occasionally form minor scarps being omitted. 

 Now we see at once that great thicknesses of hard 

 sandstone and limestone have been removed, 

 leaving the shale next below only partially 

 denuded. It seems more likely that ice would 

 have cut further down in the shale, even to the 



But do we ? 



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