574 



CENOZOIC ERA— AGE OF MAMMALS. 



also, consists of bold, rocky headlands, separated by fiords running far 

 into the country ; and off shore a line of rocky isles 2,000 feet high. 

 In Greenland these fiords are now occupied by glacial extensions of the 

 general ice-mantle. The same coast-structure is found on the western 

 side of the continent in high latitudes. The coast of British America 

 and Alaska is also bold and deeply dissected by fiords ; and ii> Alaska 

 these fiords are now occupied by great glaciers running down to the 

 sea (Fig. 943). 



The fiords of Norway have been attributed (p. 38) partly to the 

 erosive agency of waves and tides, but it is certain that they are mainly 

 due to a partial subsidence of a bold coast deeply trenched with gorges. 

 In a word, fiords are deeply-eroded valleys, which have become half 

 submerged ; and, as glaciers are the most powerful of erosive agents in 

 these regions, they are usually half- submerged glacial valleys. These 

 valleys can in most cases be traced as submarine troughs, far out to sea. 

 In Greenland, for instance, the extension of these troughs, deep below 

 the present sea-level and far out beyond the reach of the present gla- 

 ciers, shows a former more elevated condition ; and terraces and recent 

 deposits up to 500 feet show a subsidence below, and a re-elevation to, 

 the present level. 



Fig. 943.— Ideal Section through a Fiord. 



All shores in northern regions are bold and rocky and deeply dis- 

 sected, and have rocky islets off shore ; in other words, are more or less 

 affected with fiord-structure. They have been elevated, eroded, and 

 subsided. It is probable that during the epoch of greatest elevation a 

 broad continental connection existed between America and Asia, in- 

 cluding the whole area between the Aleutian Isles and Bering Strait. 



2. Glacial Lakes. — Lakes are found in nearly all countries, and are 

 doubtless due to many different agencies, but the small lakes, so abun- 

 dant in the region covered by the ice-sheet and by ancient glaciers, are 

 undoubtedly due to glacial agency. It is only necessary to look at a 

 good map of the United States to see at once the great contrast in this 

 regard between the Northern and Southern parts. In the single State 

 of Minnesota there are several thousand lakes. South of the line of the 

 ice-sheet there is not one. 



