SCIENTIFIC RESULTS 



93 



slowly but rapidly gaining niomentuni. the ice attains the incredible 

 speed of 5 to 8 miles per liour — as fast as a fox can run, affirm the 

 Greenlanders — to the accompaniment of a deafening roar that can 

 be heard for miles, and that sometimes lasts for days. Sealing nets 

 that the natives stretch under the water between the bergs are 

 quickly torn asunder, thus in a few moments a great part of the 

 ccnnnunity's investuient in fishing may be swei)t away. Xobody 

 can foretell tlie api)r()acli of the catasti-ophe. This ])lienouienon 

 unique to the Jacobshavn Fjord is termed an " outshoot " by Porsild 

 (1919. p. 151), who attributes it to the pent-up melt water, and 

 which like a spring freshet, breaks the ice dam to discharge hundreds 

 of icebergs out into Disko Bay. Jacobshaven ice fjord also differs 

 from many of the others in that it expels icebergs even in the winter 

 desi)ite the barrier of shoi-e ice unless, of course, the latter is unusu- 

 ally heavy and of great width. But outshoots are most liable to 

 take place in summer and in June at spring tide, while they are 

 rarest, of course, in midwinter. 



The Mouth of Jacobshavn Fjord 



Figure -51. — Looking eastward toward the fault in the foreland which marks the pro- 

 file of .Jacobshavn Fjord. In the foreground and being pushed outward in the 

 direction of tlie water are hundreds of tightly packed iceberss. (See tia. 52 for a 

 close-up view.) This sketch was made as the Marion approached Jacobshavn Fjord 

 on August 8, 1928. 



! The icebergs discliarged from the Jacobshavn Fjord appear to be 

 retarded at its entraiice. Haminei- (1893, p. 27) observing this fact 

 believed that the temporary halt was due to the presence of a bank 

 at the mouth of the fjord, which he likened to the stopper in a bottle. 

 But the presence of a shoal there, however, has never been proved 

 Jby soundings, for none of the depths recorded on the charts, viz, 

 200. 210. and 240 fathoms, are in the position of the supposed bank. 

 The Marion expedition took several fathometer soundings among the 

 outer icebergs that crowded the mouth of the fjord August 8, 1928, 

 but the depths of 195 to 215 fathoms, considerably greater than 

 130 fathoms, the figure assumed by Hammer (1898). do not sug- 

 gest any shoaling. The presence of a bank, nevertheless, is not 

 entirely disproved, inasmuch as the Marion succeeded in penetrating 

 only to the outer margin of the iceberg cluster, and therefore may 

 not have got in far enough to be directly over the shallowest spot. 



