70 ALASKA GLACIERS 



blocks came to our ears every five or ten minutes. As each 

 block fell, it started a series of circling waves, many of 

 which were so large as to make breakers miles away, despite 

 the damping effect of the floating ice. The breakers we 

 observed on Osier Island were formidable enough to en- 

 force much caution in landing, and the series from different 

 ice falls followed one another so closely that there were 

 few intervals of quiet. 



The southwest side of the island is sheltered from all 

 winds except westerly and, as it borders a cove which 

 westerly winds would pack with ice, may never feel the 

 force of wind waves. Ice-fall waves reach it from Turner 

 Glacier after a journey of four miles, and by shorter, 

 but deflected, courses from the Hubbard. Its shore 

 cliffs are much lower than those of the other sides of 

 the island. 



In 1794, when Hubbard Glacier reached to Haenke 

 Island, Osier Island must have been ice-covered and sub- 

 ject to glaciation, and it was not bared until more than 

 half the subsequent wasting had been accomplished. It 

 is therefore probable that the existing shore cliffs, esti- 

 mated from memory as 25 to 30 feet high, have been 

 carved out within a few decades. During part of 

 this time the ice-fall waves reaching the north shore 

 were more effective than now because the ice cliff 

 was nearer. 



From these various features, and especially from the 

 comparison of the north and east shores of the island, it 

 appears that ice-fall waves have very notable ability to 

 erode coasts, an ability fairly comparable with that of 

 wind waves. This fact is of value to the student of Pleis- 

 tocene glacial lakes, as it enables him to understand the 

 clear outlining of their coasts in cases where the indicated 

 extent of the water surface is too small for the generation 

 of important wind waves. 



