GLACIAL FEATURES OF ALASKAN COAST 431 
From the southern end of the frontal cliff a heavy deposit of mo- 
raine extends out in the form of a broken loop. The river is actively 
cutting into this deposit of till and seems to have destroyed a consider- 
able part of it. ‘The remainder forms a hook-shaped barrier on the 
south side of the river and sufficiently retards the current to form the 
Alsek Pool. This bulb-shaped expansion of the river at the mouth 
of the canyon is nearly 2 miles in diameter, and but for the gravelly 
plain on the north would be nearly square. On the north side of the 
Fic. 8.—Front of the Alsek Glacier. Vertical cliff of dirty ice 160 feet high con- 
tinually undermined by the river. 
river the complement of the moraine ridge has not been identified. 
In spite of the powerful current poured into it by the Alsek the 
surface of this lake is nearly still. The bergs which fall from the 
glacial scarp drift very slowly down toward the exit from the lake. 
Sometimes they become stranded on the shallow north beach, where 
they are broken up by the waves and melt. At times those which 
succeed in reaching the exit congregate there in such masses that the 
channel becomes congested with them, and the river is temporarily 
