THE ICE AGE AND ITS WORK 



63 



acteristic features of moraines are, their position in valleys 

 where there are other indications of glacial action, their 

 steep slopes and often level tops, but especially their com- 

 position of earth, stones, and gravel, with large fragments 

 of rock irregularly scattered through them from top to 

 bottom without any sign of stratification, while usually 

 one or more large blocks rest upon their summits in posi- 

 tions where they could only have been left by the retreat 

 of the glacier, or possibly stranded from floating ice. The 

 accomyjanying cut (Fig. 9) shows the surface of part of the 



Fig 9.— surface of part of great terminal moraine. 



great terminal moraine of the North American ice- sheet 

 in south-eastern Massachusetts, from the seventh Report 

 of the United States Geological Survey. It presents a 

 more barren and stony surface than most of our moraines, 

 which are usually grass-covered. Fig. 10 is a view of 

 Easedale Tarn above Grasmere, showing a series of 

 moraine heaps beyond the lake. Where extensive glaciers 

 have covered large areas of nearly level ground the 

 moraines form great sheets extending for many miles, 

 often concealing the original contours of the country, and 

 then receive the general name of drift. The composition 



