158 



ICE DEPOSITS 



retreating ice-sheets, such as the Malaspina ; in advancing glaciers 

 denudation will prevail over deposition. 



Iceberg Deposits. — When a glacier flows into the sea, it con- 

 tinues to advance until the buoyant power of the water is suf- 

 ficient to raise and float it : as ice can endure very little strain, 

 great masses are thus broken off and float away as icebergs. Ice- 



FIG. 



Deposit partly made by stranded ice, west coast of Greenland. 

 (Photograph by Libbey.) 



bergs are thus seen to be, as indeed they always are, derived from 

 land ice and not from the freezing of sea-water. The iceberg will, 

 of course, carry with it whatever parts of the glacial debris are 

 contained within or upon that particular' fragment of the glacier, 

 and drops this load over the sea-bottom, as the berg gradually 

 melts. As the Greenland icebergs sometimes drift as far south as 

 the Azores, glacial boulders are scattered all over the bed of the 

 North Atlantic, and thus we see how large blocks may be em- 



