ANTARCTIC ADVENTURE AND RESEARCH 



the valley. This is filled with morainic material to the 

 depth of a hundred feet or so, for the drainage of the 

 bowl is away from the sea to the salty waters of Lake 

 Bonney. The defile previously mentioned is about 

 1,500 feet deep, and would seem to be a water- 

 cut gorge denoting an interglacial period. Lake Bon- 

 ney is separated into two portions by a granite bar 

 five hundred feet high. This also is traversed by a nar- 

 row gorge on the northern side of the trough, and is a 

 smaller edition of the Nussbaum barrier or riegel. 

 Then about half a mile west we reach the snout of the 

 Taylor Glacier, which appears to be over-riding mo- 

 raine material at its extremity. (See Figure 13.) 



Visitors to Switzerland will recognize how closely 

 the alternation of gorge, riegel, and bowl recalls the 

 classic glacial valley between Airolo and Biasca. It is 

 the writer's opinion that similar forces of erosion have 

 produced these similar but far distant topographies. 

 The evolution of this peculiarly complicated structure 

 in the floor of the large glacier-cut troughs of the Fer- 

 rar-Taylor Glaciers is to be explained in my opinion 

 by a study of cirque-erosion. 



Cirques. — These land-forms are very abundant 

 throughout the glacial topographies of the world, and 

 it is rather surprising that their origin was not at all 

 understood until the research of certain American 

 geologists in the western United States about 1900. 

 The cirque is a peculiar valley which has been com- 

 pared in shape to an armchair. It has a more or less 

 circular base and steep bounding walls on three sides, 

 being open on the lower fourth side. The scarp of 



T24 



