COLD AND ICE ON THE EARTH 



period when a great deal of Europe was covered with 

 snow or ice as Greenland is to-day. What records would 

 it leave behind ? Now, on slopes the sheet of snow would 

 tend to slip just as it slips from sloping house-roofs. In 

 doing so it would push before it any loose material which 

 lay in front of it ; and trees or bushes, stone or soil, 

 would be gradually pushed downhill. If the slopes were 

 steep enough the snow-sheets would occasionally break off 

 and sweep down as avalanches. Sometimes these great 

 masses are many thousands of square yards in area and 

 fifty feet thick, and in the late winter and early spring 

 often do immense damage, carrying away houses, trees, 

 and great masses of rocks in their progress. They 

 leave their imprint not only in ground swept bare, 

 but in huge mounds of debris piled up in the valleys 

 below. 



But when the snow has taken the form of a glacier its 

 record is left in more unmistakable characters. Imagine 

 a great mass of snow and ice descending between the clefts 

 of mountains to lower levels. As it slips slowly down its 

 valley, like a very slow river slower than a river of 

 thickest mud or pitch or lava would be earth, sand, mud, 

 gravel, boulders, and masses of rock sometimes are washed 

 down on its surface from the slopes on either side. 

 Avalanches will occasionally bring other contributions. 

 Nearly all this rubbish accumulates on the edges of the 

 glacier nearest the slopes, and it is slowly borne to the 

 journey's end on the glacier's shoulders. Some of it falls 

 into rents or crevasses in the ice, and may be imprisoned 

 there and carried down as an inside passenger, or it may 



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