Geology and Physiography 3 



once by ice which has left behind a cover of Chalky Boulder Clay. The 

 removal of this drift cover has re-exposed the rock formations and led 

 to renewed differential erosion. During the retreat of the ice, deposits of 



[II]0-IOOft. p^ 50 ft. contour CZ] lOO-200ft. g^ 200-300ft. 



^^ 300-400ft. ffl8400-500ft. §■ over 500 ft. 



Fig. I. 

 The relief of Cambridgeshire and the surrounding country. 



coarse gravels and sands were laid down probably in glacial lakes. These 

 now occur as ridges, which were formerly attributed to a system of river 

 valleys older than the present Cam drainage. Gravels and sands near the 

 eastern end of the Gogmagog ridge have been explained as outwash 



1-2 



