'910.] INLAND-ICE OF THE ARCTIC REGIONS. 125 



to sea and scattered over wide areas of the ocean before their final 

 dissolution in the warmer southern waters. 



The larger bergs instead of falling from the cliffs, suddenly rise 

 out of the water as ice islands, often several hundred feet in front 

 of the ice clifif. A wholly satisfactory solution of the problem of 

 their birth involves a nice quantitative adjustment of several factors, 

 all of which are undoubtedly more or less concerned. On the one 

 hand, there is wave action which is effective especially near the 

 water level and has a direct range of action extending from a dis- 

 tance below the surface equal to the length of a storm wave in the 

 fjord, and to a height above the quiet level equal to the height of the 

 wave's dash. If there were no melting in the water, and if the 

 lower layers of the glacier moved forward as rapidly as the upper, 

 the tendency would undoubtedly be to develop an erosion profile in 

 every way like that of a rock-cut terrace upon the sea shore. With 

 emphasis upon this element in the problem Russell has assumed 

 that the ice cliff at the fjord is prolonged outward beneath the water 

 as an ice foot which thins gradually toward the toe. Upon this 

 hypothesis the bergs which rise from the water are born from the 

 foot where the increasing buoyancy of the outer portion overcomes 

 the cohesive strength of the material at the surface where rupture 

 occurs. This view accounts particularly well for those bergs which 

 rise from the water far in advance of the cliff (see Fig. 41).^^^ 



Laying stress rather upon melting in the water and upon the 

 rapid forward movement of the upper layers of ice near the glacier 

 margin, Reid has arrived at a wholly different conclusion concerning 

 the origin of larger bergs :^^'^ 



The more rapid motion of the upper part would result in its projection 

 beyond the lower part, and this would become greater and greater until its 

 weight was sufficient in itself to break it off. The extent of the projection 

 before a break would occur, depends evidently upon the strength of the 

 ice. . . . That the ice for several hundred feet below the surface does not 

 in general project farther than that above is evident from the fact that I have 

 frequently seen large masses, extending to the very top of the ice front, 



"°I. C. Russell, "An Expedition to Mt. St. Elias, Alaska," Nat. Geogr. 

 Mag., Vol. 3, 1891, pp. 101-102, fig. I. 



"'H. F. Reid, "Studies of ]\Iuir Glacier, Alaska," ihld.. Vol. 4. 1892, 

 pp. 47-48. 



