WATER AS A MECHANICAL AGENT. 



249 



A remarkable example of the carrying of stones up an under-glacier slope is afforded 

 by the region of the " Nunataks " of Greenland (map, page 241). The dotted belts on the 

 following figure (m', m", m'", ?n'^) repre- 



214. 



sent belts of moraine made by this process ; 

 and the nunataks g, h, i, k, I, m, are emerg- 

 ing peaks of the covered ridges. The moraine 

 m'" was made by a submerged peak. The 

 stones are not like those from the nunataks. 

 They came up from varying depths in the 

 ice. Some of them are 20 feet across. The 

 stones of the nunatak moraines disappear 

 down crevasses after 200 to 300 yards of 

 sunlit travel, or bury themselves in the ice. 

 In a similar way, where a glacier crosses 

 marine channels, shells gathered into the 

 ice might be carried along to the tops of 

 the elevations over the land ; or possibly, 

 loose sea-border material beneath might be 

 pushed up by the glacier. 



The abrasion carried on by the 

 stones in the sides of the glacier 

 planes off, polishes, grooves, and often 

 profoundly channels, the rocks either 

 side or below ; and these scorings 

 are evidence of the direction of move- 

 ment. An example of the grooves or 



scratches is represented in Fig. 215. Crossing lines, which are not unfre- 

 quently observed, are produced when glaciers spread widely over a broad 

 region, and, owing to change in the thickness of the ice or some other cause, 

 there is a change of direction in the movement. 



Nunataks, or isolated peaks, g, h, i, k, I, m, situated 

 like islands in the Greenland ice. Jensen. 



'^ff 



215. 



GHacier groovings or scratches. 



Moreover, the stones or rock-masses that do this work of abrasion become 

 smoothed and scratched or grooved; and thereby may show their glacier 



