104 PHYSIOGRAPHY 



The table below shows the position of the snow-line at a few 

 points: 



Bolivian Andes, west side, Near Equator, About 18,500 feet. 



Bolivian Andes, east side, Near Equator, About 16,000 feet. 



Chilean Andes, Lat. 33 S., About 12,800 feet. 



Himalayas, north side, Lat. about 28 N., About 16,700 feet. 



Himalayas, south side, Lat. about 28 N., About 13,000 feet. 



Caucasus Mountains, Lat. 40+ N., About 8,300-14,000 feet. 



Pyrenees Mountains, Lat. 40+ N., About 6,500 feet. 



Lapland, Lat. 70 N., About 3,000 feet. 



Alaska, Lat. about 60, About 5,500 feet. 



Greenland, Lat. 60-70 N., About 2,200 feet. 



Ice-fields. Every large snow-field is also an ice-field, for where 

 snow accumulates to great depths and lies long upon the surface, it 

 is changed to ice. The beginning of this change may be seen in 

 the snow a few days after it falls, for it soon loses its light, flaky 

 character and becomes granular, so that it feels harsh to the hand. 

 The change is very distinct in the last banks of snow in the spring. 

 They are made up of coarse grains (granules) of ice, sometimes as 

 large as peas. The change from flakes of snow to granules of ice is 

 due, in part, to the melting of the snow and the refreezing of the 

 water. If there is much snow, it is compressed by its own weight, 

 and after being compacted in this way, the freezing of the sinking 

 water binds the granules together. By this and perhaps other 

 processes, the larger part of every thick snow-field becomes an ice- 

 field merely coated over with snow. 



GLACIERS 



When the amount of ice developed from snow becomes great 

 enough, it begins to move out by a sort of spreading motion from 

 the place where it was formed. When it begins to move, it becomes 

 a glacier. Not all snow-fields give rise to glaciers, but all glaciers 

 have their sources in snow-fields. The distribution of glaciers is 

 therefore much the same as that of snow-fields. 



Types of glaciers. Glaciers have various shapes, depending 

 on the amount of ice and on the shape of the surface beneath them. 

 If the snow-field which gives rise to a glacier is at the upper end of 



