AVALANCHES 431 



at the same altitude than on the windward side. Thus 

 high mountains affect not only the rainfall, but the tem- 

 perature changes of the region round about. 



205. Avalanches. In mountain regions where the in- 

 clination of the surface is steep, the loose material is liable 

 to slide down the mountain sides, especially when it becomes 

 moist because of long rains, or of the thawing of the frozen 

 ground. As the material slides, the quantity increases, 



LANDSLIDE. 

 Covering one of the main roads of Norway. 



and momentum or force of movement is gained until a 

 vast mass sweeps with almost irresistible force down the 

 side, wrenching away trees, bowlders and whatever lies in 

 its path. On reaching the valley the debris is piled in 

 irregular mounds. 



The scars of these avalanches are seen on the sides of 

 almost all high mountains. In mountain regions which 

 are inhabited, avalanches are frequently very destructive 

 of life and property. In the Alps large forests are often 



