NEW PHYSIOGRAPHY AND GEOLOGY OF GREENLAND 63 



continent like Greenland will always be a hindrance to the formation 

 of fissures across the country. It would then be only natural that 

 the fissure would take its course where Greenland, considered as 

 a continent, was weakest. 



The theory that the depression is simply a direct continuation 

 of the great Tertiary fissure is, however, the most natural explana- 

 tion. We know that there have been great movements of the earth's 

 crust in mid- Greenland since the Tertiary period, marine fossi- 

 liferous strata having risen several hundred meters since then. If 

 the depression is a Tertiary fissure, the consequence would be that 

 the gneiss planes would be displaced vertically along the fissure 

 about 2,000 meters in relation to each other. It is, however, 

 questionable whether so huge a displacement could take place 

 without the ground on the sides being broken. No such phenome- 

 non is known from Greenland, but that may, of course, be due to 

 defective investigation. 



The inclination of the northern gneiss plane toward the north 

 may be explained by the fact that its northern part is heavily 

 weighted with sediments. If a fissure were formed right across 

 the country the gneiss plane which carries the sediments would be 

 reduced to about half and therefore be tilted so that the northern 

 part would be lowered and the southern part raised. In the same 

 way it may be assumed that the northern part of the southern gneiss 

 plane has been submerged beneath the weight of pouring out basalt 

 masses. It has been shown above that both in the west and the 

 east basalt is found deposited on the surface of the southern gneiss 

 plane. Toward the west there are no great quantities left, but 

 escarpments of i ,000 meters show that the basalt once had a greater 

 extension toward the south. Eastward much larger basalt areas 

 now rest on the southern gneiss plane, and how far the basalt here 

 penetrates below the inland ice is still unknown. If we imagine 

 the displacement along the fissure taking place in such a way that 

 the southern edge of the northern gneiss plane was raised just as 

 much as the northern edge of the southern gneiss plane was lowered, 

 the displacement for each gneiss plane at most would amount to 

 1,000 meters. As it is known for a fact that gneiss planes may, 

 under pressure of ice for instance, subside and again rise more 



