GLACIER 



2501 



GLACIER NATIONAL PARK 



extensive glaciers around Cook's Inlet. Com- 

 pared with these Alaskan glaciers those of the 

 Alps are mere rivulets. The Malaspina, on 

 Yakutat Bay, Alaska, is 1,550 feet high and 

 has an area of 600 square miles; the Valdez, 

 on Prince William's Sound, is fifteen miles 

 long; the Muir, named for John Muir, at the 

 head of Glacier Bay, is 200 feet high and has 

 a frontage of three miles on the coast. All 

 the valleys of the Northern Alaskan coast are 

 filled with ice rivers, and the fiords of this 

 region were formed by the action of glaciers. 



In Glacier National Park, Montana, and in 

 Rocky Mountains Park, just to the north, in 

 Canada, are numerous glaciers which can be 

 easily reached and are interesting to study. 

 Enormous glaciers are also found in. the Sel- 

 kirk Mountains in British Columbia, along the 

 line of the Canadian Pacific Railway. These 

 glaciers are visited by thousands of tourists 

 every season. The most noted glaciers .of 

 Europe are the Mer de Glace on Mont Blanc 

 and those on Mont Rosa. 



Structure. Glaciers are formed by the freez- 

 ing and pressing together of masses of snow. 

 After snow has lain upon the ground for some 

 time, the flakes lose their form and the snow 

 becomes granulated, as we see it in snow- 

 drifts in the spring. On the mountains where 

 snow remains from year to year this granu- 

 lated snow becomes frozen into a porous ice 

 which the French call neve, the name generally 

 given it by geologists, but which we call glacial 

 ice. A layer of glacial ice is formed each year, 

 and the lower layers become more compact 

 than the upper, so these lower layers more 

 closely resemble ordinary ice. 



Crevasses. The irregular surface over which 

 the glacier moves often causes the ice to crack 

 and form crevasses, which are sometimes more 

 than 100 feet deep. Since these are often 

 filled with light snow they are very dangerous 

 to travelers. The sun melts the ice at the top 

 of the crevasse faster than it does that below, 

 hence the crevasse becomes wedge-shaped and 

 continues to increase in size. Sometimes the 

 crevasses are closed by the movement of the 

 glacier. 



Surface. The surface of the glacier becomes 

 very irregular. This is due to the crevasses, 

 to stones and other materials which the glacier 

 gathers as it moves down the mountain and 

 to irregularities due to the unequal melting of 

 the ice. The porous ice melts much faster 

 than that which is more compact, and in 

 time the surface is covered with hollows and 



slight elevations. Stones shield the ice from 

 the rays of the sun; so wherever they are 

 lodged there are irregular surfaces. 



Terminal. The lower end of the glacier is 

 usually very steep, and from under it there 

 issues a stream of ice-cold water formed by the 

 melting of the glacial ice. 



Movement. A glacier is the slowest-moving 

 solid body in all the world ; it moves down the 

 valley very much as a mass of tar almost 

 solid would move down an incline. The upper 

 and middle parts of the stream travel the 

 fastest, the sides and bottom being held back 

 by friction on the sides and bottom of the 

 valley. The rate of motion can be measured 

 by measuring the movement of any object on 

 the surface. It usually is from eighteen to 

 twenty-four inches a day. The lower end of 

 the glacier may move up the valley in summer 

 and down in winter; or it may remain sta- 

 tionary. This depends upon the rapidity with 

 which the ice is melted. When the end of a 

 glacier juts so far into the sea that it breaks 

 off from the main body the mighty fragment 

 forms an iceberg, which then floats down from 

 the frozen north towards civilization to be- 

 come a menace to navigation. The story of 

 an iceberg is told under that title. 



Moraines. On its way the glacier gathers 

 rocks and other material, which usually form 

 lines which may be tracked through the mass; 

 those near the sides are known as lateral, and 

 those toward the middle are medial, moraines. 

 The debris deposited at the end of the glacier 

 forms the terminal moraine. 

 .;' Erosion. As a glacier plows its way down 

 the valley it carries along with it all the loose 

 material on its bed. Thus it deepens the val- 

 ley, lays bare the rocks and polishes them and 

 marks them with striae (scratches). The work 

 of erosion now performed by glaciers, however, 

 is inconsiderable. E.S. 



Consult Gilbert's Glaciers and Glaciatlon; 

 Hobbs' Characteristics of Existing Glaciers; Rus- 

 sell's Glaciers of North America. 



Related Subjects. The following articles in 

 these volumes will be interesting and helpful in 

 connection with the above : 

 Erosion Icebergs 



Fiords Malaspina Glacier 



Geology Mer de Glace 



Glacial Period Moraine 



Glacier National Park Muir Glacier 



GLACIER NATIONAL PARK, one of the 



most beautiful of the American national parks, 

 reserved for the pleasure and recreation of the 

 people. The region is one of romantic beauty; 



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