Prof. A. K Nordenshiold — Geology of Spltzbergen. 265 



'' As at Scott's Glacier, there occurs also at Cape Lyell a number 

 of leaves, whose determination demands a much closer examination 

 than I have been hitherto able to give them. A more complete 

 description of these we must therefore defer." 



As the above profiles show, the Tertiary strata on Spitzbergen 

 are very irregularly dislocated and contorted, although they are 

 surrounded by older rocks, which, though raised up, are in all 

 cases regularly stratified. It follows that the disturbance in the 

 position of the most recent strata has not extended very deep down, 

 and that, as the ideal section given below shows, a distortion of the 

 surface strata took place without extending to the rock lying below. 



Fig. 19. — Ideal section showing the disturbances in the jiosition of the Tertiary 



strata on Spitzbergen. 



A. Older strata, belonging to the Mountain Limestone or Hecla Hook formation. 

 JB. Tertiaiy strata. 



Under such circumstances it is clearly impossible that the distor- 

 tion was occasioned by plutonic forces in the interior of the earth. 

 I have before maintained that such disturbances can easily be ex- 

 plained by the action of repeated inconsiderable changes in the 

 temperature of the strata, and their expansion and contraction 

 thereby occasioned. For if a stratum alternately contracts and 

 expands through change of temperature, it is natural that during the 

 contraction, as soon as it passes the limit of elasticity, cracks must 

 arise. These cracks generally close again, when the strata expand, 

 but this is not unfreq^uently prevented by the formation of incon- 

 siderable chemical or mechanical deposits in the open craek, and 

 in this case a dislocation of the strata must take place, which on 

 changes of temperature following is repeated again and again, 

 and thus gradually bringing about very considerable changes in 

 the original horizontal position of the strata. A clear representation 

 of the alterations which in this way may take place under favourable 

 circumstances during a single winter is afforded by the hummock 

 walls and packs of the polar ice, which are clearly formed in this 

 way, that the originally level ice-field alternately contracts with cold, 

 whereby cracks arise, which, however, within a few hours freeze 

 together again, and expands in mild weather, whereby a dislocation 

 must naturally take place. 



Such great changes of temperature as occur upon an ice-field 

 exposed to the unceasing oscillations of temperature of the atmosjDhere, 

 do not naturally take place in a solid earthy layer, and the cracks 

 which arise in the latter are perhaps not so completely filled again as 

 those in an ice-field ; but on the other hand the action takes place 



