HIGH PENEPLAIN 129 



riding ice-sheet. The deep dissection indicates a subse- 

 quent history different from that at the north, but the 

 evidence of an initial peneplain is at least equally clear. 

 The approximation of the summit heights to uniformity is 

 too close to be accounted for without the hypothesis of an 

 uplifted plain; but the departures from uniformity indicate 

 that little if any of the original plain survives. 



The general interpretation of these upland features ap- 

 pears to be as follows : After the folding and squeezing 

 of the metamorphic rocks, there was a long period of 

 erosion, in which broad tracts of the land were worn 

 down nearly to sea-level. Then came uplift, producing 

 a plateau from 3,000 to 6,000 feet high, and erosion has 

 followed. In some places, at least, this plateau sloped 

 gently toward the sea, and its plane may have remained 

 everywhere continuous, diversified only by moderate 

 flexures; but there is also possibility that it was inter- 

 rupted here and there by faults. The period of subsequent 

 erosion has been long enough for the development of local 

 peneplains at a lower level, and in that time the plateau 

 has been greatly modified. Not only has it been dis- 

 sected by the eating out of gorges and valleys, but its 

 back has been worn and fretted, largely by local glaciers, 

 until all the original surface and much of the original form 

 have disappeared. What remains is chiefly a tendency 

 to uniformity of crest height in the ridges and peaks of 

 certain districts. 



It is probably true also that vestiges of the high pene- 

 plain are conspicuous only where the rocks are com- 

 paratively durable. Our best examples are along the 

 mainland east of the archipelago, and that region, accord- 

 ing to Dawson, is largely granitic. The dominant rocks 

 of the archipelago are metamorphic, and we saw little 

 from the ship's deck to suggest that the uplands of the 

 islands have a plateau habit. The mountains next the 



