:22 GLACIAL REMAINS IN THE NATIONAL PARK, 



DESCRIPTIVE ACCOUNT OF THE GLACIAL 

 REMAINS. 



I. THE BROAD RIVER VALLEY (See Plates VI. and 

 VIII.) 



(a) Below Lake Webster. 



The whole seven miles of the Upper Broad River Val- 

 ley is a typical glacial trough, most markedly U-shaped, 

 straight, and devoid of spurs. The floor, averaging half a 

 mile in width, is quite flat, and the sides, gently sloping 

 at first, rise abruptly 500 feet in a slope that is often 

 precipitous. At the top of these sides depressions and 

 spurs have begun to appear, but these have been shorn 

 off" lower down. 



Glacial remains can be traced over four miles below Lake 

 Webster. In this distance, the floor of the valley is nearly 

 level, dropping only 150 feet. It is covered with button- 

 grass growing on a stiff clay, and crossed at intervals 

 by definitely marked and easily visible moraines. The 

 Broad River winds through these button-grass plains, and 

 cuts through the moraines first on one side, then on the 

 other, and where it does so it drops quickly in a succes- 

 sion of stony rapids, passing out again on to the flats 

 hardly to drop at all until the next moraine is reached. 

 The river has cut down in places to a depth of six feet 

 below the surface of this plain, and there you can see 

 what underlies the vegetation. 



Evidently, the glacier deposited in its retreat the var- 

 ious moraines which have successively blocked the valley 

 from side to side. Behind these dams, large, shallow lakes 

 were once banked up. The glacier dropped the larger 

 boulders, as it melted, in the spot where we now see them as 

 moraines, while the water escaping from the melting ice 

 carried the finer materials out into these lakes as silt, and 

 formed great beds of clay and sand on their floors. Across 

 the surface of the lakes floated blocks of the glacier as ice- 

 bergs, and dropped stones and pebbles into the clay. A 

 large volume of water was liberated as the glacier melted, 

 and these lakes overflowed at the lowest side of the moraine. 

 In time this overflow cut away the loosely knit material 

 of the dam, and eventually drained the water from the 

 lakes, leaving the peculiarly level beds of clay we now 



