1 92 1. No. II. THE STRAXDFLAT AND ISOSTASY. 21 3 



ice-cap. It is therefore possible that tlie outer part of this coast land 

 mav have risen towards its natural level of equilibrium, and even that, 

 by the pressure of the ice-cap over the inner land, the outer coast may 

 have been upheaved above its natural isostatic level, although this is 

 hardly probable. 



These are interesting questions which have to be settled by special 

 investigations on the spot. 



On the islands of the Arctic Arcliipclago north of Canada, there is 

 obviously also a strandfiat. 



On the islands along the coast of Alaska, there is a strand flat 

 forming a flat foreland between the base of the steep mountains and 

 the descent to deep water. 



Gilbert [1904, pp. 130 ff. and 17g] mentions this low foreland in 

 several places and gives some very illustrative pictures of it (see his 

 Figs. 64, 65, 85, and his Pl.XMI) showing that it is obviously of the 

 same type as the Norwegian strandfiat. Gilbert, however, explains 

 it as a preglacial peneplain, or base-levelled plain, in the same manner 

 as Ahlmann has lately adopted. This peneplain formed originally a more 

 continuous foreland, which has afterwards been dissected by erosion, 

 forming deep channels now separating the islands. These channels have 

 to a great extent been formed even by fluvial erosion "at least 500 feet 

 (150 metres), and probably 1,000 feet (300 metres) or more, below the 

 present sea-surface" [1904, p. 136I. It seems to me difficult to under- 

 stand how a plain of this kind could possibly have survived a fluvial and 

 glacial erosion which has cut channels through it, now 1,500 to 1,700 feet 

 (450 to 520 metres) deep. Gilbert has also to assume that "the glacial 

 degradation must have been locally quite moderate, or the general plain 

 character would not have survived" [1904, p. 131]. 



In my opinion there can be little doubt but that this low foreland 

 in Alaska is a formation of the same nature as the Norwegian strandfiat, 

 and has been formed in the same manner by shore erosion, during cold 

 interglacial periods, and during the beginning of glacial periods, before 

 the land began to sink, and before the coasts were covered bv glaciers. 



The heights of the Alaskan strandfiat seem to be similar to those of 

 the Norwegian one. Gilbert states that on the islands along the coast 

 of Kadiak "the height ranges from about 100 feet (30 metres) to sea- 

 level" [1904, p. 179'. On the Annette Island, in the Alexander Archi- 

 pelago, he says, however, that "there is a general and gradual ascent 

 from the sea front to the mountain base, where the altitude may be 

 three or four hundred feet" (90 or 120 metres'). This description does 

 not, however, agree with the impression given by his illustrations, which 

 show a low fairly level plane, and I think, therefore, that this high alti- 

 tude of the mountain base is not the general one. 



