316 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 5 



40-50 feet were soaking wet and grass-covered. Numerous springs 

 issued at the top of the grassy portion, making it extremely difficult 

 to negotiate the steep slope. The line of springs marks the top of 

 relatively impervious morainic material from which the boulders in 

 llie stream bottom were derived. 



The walls of tliis gorge provide the cross-section of the kame-and- 

 kettle topography. With the underlying material identified as boul- 

 der till, it is safe to assume that the puzzling hills and depressions 

 resulted from glacial deposition and that the pumice veneer is but 

 a postglacial camouflage. 



The full significance of this buried hummocky moraine may rest 

 in its suggestion of the terminal position of the Munson Valley 

 glacier. To be sure, there is no proof that the deposit does not repre- 

 sent a recessional stage of the glacier ; and no evidence thus far ob- 

 tained would deny a much more extensive glaciation than is here 

 described. Some day the valley of Annie Creek may reveal new 

 clues ; but until definite evidence of ice action is found farther down 

 the valley, there is no reason for assuming that ice proceeded beyond 

 the position indicated on Middle Fork. The possibility of securing 

 new evidence at greater distances from the rim is very slight in view 

 of the vast pumice and ash deposits which bury so much of the 

 former glacial landscape. 



South of the Devils Backhone (19). — ^Within the rim just south of 

 the Devils Backbone and only 300 feet above the lake level is the 

 oldest record of glaciation discovered in the region (pi. 6, fig. 1). 

 Buried beneath 800 to 900 feet of lava and volcanic material of 

 various kinds is a deposit resembling till, although striae do not 

 appear. Underlying this formation, however, is a striated bedrock 

 surface indicating that even during the early stages of volcano 

 building, the cone of Mount Mazama attained sufficient height to 

 allow glaciers to form and descend to elevations of approximately 

 6,500 feet. One naturally wonders how high the mountain was 

 during this early stage, but adequate evidence on which to base any 

 calculation is entirely absent. 



Palisades (20) . — A short distance to the west of the Wineglass is 

 a massive flow which produces a precipitous cliff 300 to 400 feet 

 high, known as the " Palisades." At the foot of this cliff is a long 

 talus slope underlain in part at least by heavy boulder moraine 

 (pi. 6, fig. 2). Approaching the exposure from the lake, the sub- 

 angular form of the boulders is the first characteristic to be noted. 

 Closer inspection reveals striae. The surface on which the till rests 

 is undoubtedly beneath the level of the lake. This glacial deposit is 

 lower in elevation than any found within the rim, but it is not so 

 deeply buried under volcanic material as the old striated surface 

 south of the Devils Backbone. 



