I92I. No. II. THE STRAXDFLAT AND ISOSTASY. I47 



Oxaal [19 1 5. p- 87' thinks the prol)able explanation of this fact to be 

 tliat the eastern, lower part of the submerged strandflat has been cut away 

 bv the deep channel, excavated along the inner side of the Træna Plateau, 

 and this channel should then to some extent be younger than the strand- 

 flat. The probal)ility of this explanation might seem to be supported by 

 the fact that the channel is deepest, with deptlis of 420 metres, just east 

 of Selvær. where tlie submerged strandflat is especially level and high, 

 with a sharply marked edge at about 10 metres below sea-level, while 

 further south, southeast of Dorvær. where the channel is less deep 

 (28S metres), the edge of the strandflat is at depths of about 30 metres, 

 and still further south or southwest, south of Dorvær and east of the 

 Træna Islands (Husoy). where there is no deep channel, the submerged 

 strandflat has no sharply defined edge. Along tlie south-eastern side of 

 the Træna Plateau tliere is also a very deep channel with depths more 

 than 300 metres (and even 438 metres), but the submerged strandflat has 

 no sharply defined edge in this region. 



Relation between the Differences in the Surface Topography 



of the Submerged Plateaus and Differences in the 



Nature of their Rocks. 



A\'hen we come to look at it. however, it is striking that the dif- 

 ferences in the surface relief and the depths of the edge of the submerged 

 stranflflat of the Træna Plateau coincide to some extent with differences 

 in its geological structure. Selvær and the northern part of the Træna 

 Plateau, where the eastern edge is so sharply defined at about 10 metres 

 below sea-level, are built up of mica-scliist and young gneiss, while Cor- 

 \ær is built up of granite and the islands of Sandøi and Træna to the soutli- 

 west of pressed granite, and here the surface of the submerged strandflat 

 is deeper and it has a less distinctly defined edge. There is a similar 

 difference in the slope of the sea bottom outside the western side of the 

 plateau. It is much steeper off its northern part built up of young gneiss 

 than west of the southern part built up of pressed granite. 



It may l)e difficult to find a satisfactory explanation of these features. 

 It might seem prol)able that the greater depths and the more sloping 

 surface of the submerged strandflat of the Træna Plateau, as compared 

 with that of Lovundva^r and Solvær region inside and the regions of 

 Gåsvær, Lyngvær, Flovær, Skjærvær. Fuglvær. &c.. to the south (see 

 Fig. 113). may, to some extent, be due to the effect of a violent wave 

 erosion, which has been especially effective on the much exposed Træna 

 Plateau, and which has eroded the strandflat after its first planing by 

 the joint effect of the shore-erosion by frost and the wave action. 

 It might be objected that the plateaus, for instance at Lyngvær. Flovær, 

 Skjærvær. (Sic, have been almost equally much exposed to the furv of 



