HIGH PENEPLAIN 
I29 
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 
