384 EARTH FEATURES AND THEIR MEANING 



Many mountain districts which now support small glaciers only, 

 or none at all, were once nearly or quite submerged beneath snow 

 and ice. If once covered by an ice carapace or cap, our present 

 interest in them begins at that stage of the receding hemicycle 

 when the rock surface has made its reappearance above the surface 

 of the snow-ice mass. At this stage intensive frostwork, the charac- 

 teristic high level weathering, begins, and cirques develop above 

 the scars of those earlier amphitheaters formed in the advancing 

 hemicycle. 



The piedmont glacier. In this early stage of transition from 

 the ice cap to the mountain glacier, the ice flows outward to the 

 mountain front in ill-defined streams divided by the projecting 

 ridges, and upon reaching the mountain front these streams deploy 

 upon it so as to coalesce in a great stagnant ice apron whose upper 

 surface slopes gently forward at an angle of a few degrees at the 

 most (Fig. 408, stage I). This is the piedmont glacier , a type 



FIG. 409. Map of the Malaspina glacier of Alaska, the best known of existing 

 piedmont glaciers (after Russell). 



found to-day in the high latitudes of Alaska and in the southern 

 Andes (Fig. 409 and pi. 18 B). 



During this stage the cirques may be but poorly denned, and 

 ice flows in both directions from rock divides so that the streams 

 transect the range, and later, after the glaciers have disappeared, 

 may expose a pass smoothed and polished upon its floor and with 



