SCIENTIFIC RESULTS 



101 



|)iecipitous-sided type. The glaciers of Disko Bay and Northeast 

 Hay discharge most of the picturesque forms, while northward in 

 Melville Bay, where the ice sheet itself is thrust directly out into the 

 sea. many of the square, blocky icebergs are produced. The marked 

 difference in form, therefore, may be largely attributed to the type 

 of tlie coastal land underlying the margin of the inland ice. Plateau- 

 like bergs may maintain their ecjuilibrium for a year or longer, for 

 such have been sighted even off Newfoundland with the oiiginal 

 dust and wind-blown sand of Greenland coloring their tops. 



But the triangular, dome-shai^ed berg and the straight-sided 

 type enter the Atlantic as bulky, massive bodies, worked upon hence- 

 forth by the various agencies of destruction. Bergs in the far north, 

 with few exceptions, maintain their oi-iginal outlines but after in- 



The Dome-Shaped Class of Icebergs 



Figure 61. — A Davis Strait bera observed liy tbe Marion expedition the summer of 

 1928. Its domed and rounded shape is characteristic of the hirgest class of bergs 

 to be found in the northwestern North Atlantic. Its proportions of air-exposed 

 body to be submerged are 1 : 5 to 1 : 4. (Official i.hotograph. ilarion expedition.) 



vading the warm oceanic waters of the Atlantic they melt so rapidly 

 that they change a])})earance often. The boxlike berg is first washed 

 and melted around the water line, and this continual undercutting 

 of the peri)endicular sides results in a corresponding breaking away 

 of the })r<)mineiices above. After a time the unequal detaciiments 

 rause the ice to lose equilibrium and the roof tilts, forming a 

 V-shaped berg. The absence of the square, upright types after mid 

 season at the Atlantic terminus is noteworthy. 



The well-known girdling incision at the water line is a common 

 characteristic from which few bergs are free. Overhanging ledges 

 strained beyond the structural strength of the ice detach, causing 

 the berg to roll, so that it floats in a new plane, leaving the old 

 water line clearly visible for miles. We have seen bergs off' the 

 Urand Bank wath as many as three or four old water lines marked 



