Glacier JVork. — Scott. 243 
traceable to glacial origin ; many of them have been formed 
by erosion directly, while others result from the damming of 
water by accumulated morainic material. 
Ice-dammed lakes occasionally occur in the Alpine 
glaciers, and if suddenly released after a time, as it is possible 
for them to be, they may become the cause of great devasta- 
tion. There is one such existing lake on the Aletsch glacier 
at present, the Marjelen Sea. 
Another interesting possible result of glacial erosion is 
the fjord basins of Scotland and Norway. "These basins," 
says Geikie, "have obviously been ground out by large glaciers 
in the same way as the valley basins of the Alpine lands." * 
Their origin is evidenced by the "ice-worn rocks rising to the 
surface of low islets and skerries." These fjords are always 
deeper than the sea immediatelv outside, and are comparable 
to great glaciated valley basins of the Alpine type. The islands 
which are invariably scattered along a fjord-indented coast, 
were evidently more or less covered by the ice-sheet, and in 
front of these islands very marked depressions usually occur, 
which ])robably owe their origin largely to glaciation. 
It should here be said that authorities dififer upon the ques- 
tion as to whether the Norwegian fjords are primarily of glacial 
origin. There are many facts to indicate, and it is believed 
by some eminent American geographers and geologist.^, that 
the erosive work of water in this instance, preceded that of ice; 
and that the glaciers have simply supplemented the work of 
rivers to a great extent. 
Studies by Prof. Davis t in France, Switzerland and 
Norway have convinced him of a great discordance between 
the main and tributary valleys when the former have been 
, occupied by ice-streams and the latter have not, or have not 
been effectively modified by glaciers. The great cscarpjuent at 
Niagara shows that its greater features are preglacial, though 
Gilbert believes that "glacial erosion wn)Ught important 
modification." t 
Moraines. 
"The most obvious work performed by an Alpine gla- 
cier," says Geikie, § "is that of transport and accumulation." 
*Earth Sculpture. James Geikie, p. 21S. 
tJoumal of Geology, Vol. 8, 1900. 
tlc< SciilKtiiif in Wf.stein N. York. C K. fillbert. 
$Earth Sciilpiurv, 1^9S. cit. 
