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. 
