GLACIAL FEATURES OF ALASKAN COAST 425 
were about 40-50 feet above the surface of the lake in 1906. The fact 
that vegetation has not invaded these channels suggests that they are 
of very recent origin, and this inference is borne out by the freshness 
of the loose terraces bordering the lake. It is suggested that the 
Dangerous River outlet may at times become so clogged with icebergs 
as to form a dam, and that the level of the lake is therefore subject to 
fluctuations. This may perhaps explain the reputation for disas- 
trous floods which the river has among the natives of the Yakutat 
Fic. 4.—Shattered side-lobe of the Yakutat Glacier. Shows the scarp and the 
mass of freshly broken ice which resulted from the collapse in 1906. 
foreland; for the breaking of such an ice-dam would liberate suddenly 
a large volume of water. 
Tributary valleys coming in from the southeast and northwest 
have been obstructed by the glaciers, and thus several marginal 
lakelets have been produced. On the west side of the glacier we 
observed at least four of these blockaded lakes. The uppermost and 
largest one was found completely filled with a mass of clear broken ice 
and held in by a much-crevassed scarp of ice about 200 feet high. 
