318 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 5 



The ice which crossed the rim between Discovery Point and the 

 Devils Backbone undoubtedly originated on this peak which once 

 existed above the present Wizard Island (figs. 4 and 5). If this is 

 the case. Wizard Island is probably the result of renewed activity 

 from the same channel from which, in an earlier period, came the 

 lava which produced Little Mazama. 



Following this method of investigation a little further, another 

 map has been constructed showing the direction of the striae which 

 exist within the crater rim and are definitely related to the earlier 



FiGUKE 13. — The direction of ice movement during the early stages of glaciation on Mount 

 Mazama. The projected striae suggest that the ice spread outward from a mountain, 

 the central peak of which was somewhere above the middle of the present lake. 



stages of glaciation (fig. 13), For example, the reading recorded at 

 Pumice Point is 300 feet below the rim, and the one just south of the 

 Devils Backbone is over 800 feet below the rim or 300 feet from the 

 water's edge. While the number of striae readings are necessarily 

 fewer than those available for more recent glacial stages, the results 

 obtained from their projection may be of equally great interest. The 

 projected striae roughly converge above the center of the lake, again 

 suggesting a central position for the main peak of the mountain of 

 Mount Mazama down whose slopes the early glaciers moved. No 

 projected striae converge over Wizard Island. This indicates that 



