FIRST WESTERN EXPEDITION 



i75 



backwards and eats out a long parallel valley such as the Davis 

 Valley (section II). If the plateau ice-cap increases sufficiently 

 it will drain to the sea as an outlet glacier. This will obviously 



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Young Icecap 



JX 



ger Valley 



IE 



R'&get 



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*NivA.fTor\ 

 S&sin 



The " Palimpsest " theory. Generalised sketch sections, showing the chief 

 types of valley erosion. I. Early erosion like that shown by Walcott 

 Glacier, 78° 10' S. II. Headward erosion producing a "finger" valley, 

 shown by Davis Glacier, 78 S. III. Plateau ice overwhelming the 

 cwm glaciers giving profile like the Ferrar Glacier, 77° 40' S. IV. 

 Pronounced erosion by "thaw and freeze" (= nivation), as shown in 

 the Taylor Valley, jj° 30' S. 



tend to follow the lowest contours and so would naturally 

 overwhelm a series of cwm glaciers (such as shown in II). 

 Hence we get a glacier falling over steps (and cutting gradually 



