1 92 1. No. 1 1. 



THE STRAXDFLAT AND ISOSTASV. 



257 



Z 30 ^ JO .0 /0 20 30 ^iokdomeues 50 G 



Fig. 167. Diagram illustrating the upheawil of the shore-lines between Helgoi (Ol and Havnnes \G 



i. c. is the height of the lategiacial and postglacial relative sinking of the 

 sea-level. At Mikkelvik on Ringvasoi, about 15 kilometres south-west 

 of Helgoi, or very nearly in the direction of the isobases in this region, 

 Heiland found a raised shore-line at 10.7 metres above sea-level, which 

 is obviousl\" the same as his lower shore-line on Helgoi, 8 metres above 

 sea-level. Let us therefore take the mean between the two and make the 

 height of tlie lower shore-line in this region 9.3 metres. Let us further- 

 more assume that the distance between the isobases drawn through Helgoi 

 and Havnnes is about 54 kilometres. 



According to our assumption there has been no postglacial tilted 

 upheaval of the land on Helgoi (Fig. 167, O), the upper raised shore -line 

 standing at the level of the strandfiat; there has only been a sinking of 

 the sea-level. During the first period of upheaval, before the time when 

 the lower shore-line was formed, the upper shore-line rose to the line Be. 

 The sea-level had then sunk y.y metres to the line DEf, along which the 

 lower shore-line ^^as eroded. During the last periorl of upheaval the 

 upper shore-line rose to the line BC, tlie lower shore-line to Ef. and the 

 sea sank to its present-day level ////. 



The result of these movements is that we now find the upper raised 

 l)each along ABC, the lower raised beach along DEF, and the present 

 sea-level at HH. 



If we continue the tilted lines BC and EF, they intersect one another 

 at .r, () metres above present sea-level. The plane of the upper shore-line 

 will intersect the present sea-level at 3', about 13 kilometres inside that 

 of the lower shore-line (c). 



Fig. 167 is naturally a simplified diagram. Li reality there will 

 probably be a more gradual transition from the horizontal outer parts 

 AB and DE to the rising planes inside, BC and EF. 



These results are in perfect accordance with Helland's computations 

 mentioned above, anfl the explanation of the facts here given may be 

 considered to be fullv satisfactorv. 



On the other hanrl, the facts described above seem to support the 

 probability that we are right in assuming that the lower level of the 

 strandfiat (about 15 to 17 metres above the sea) actually marks the level 



Vid.-Selsk. Skrifter. I. M.-\. Kl. 1921. No. 11. 17 



