EXTINCT VOLCANO — AT WOOD 313 



implied. Like the periods of vulcanism and glaciation, the periods 

 when soil developed and vegetation became established on the moun- 

 tain required time. These records make it possible to reconstruct 

 partially the time intervals in the growth of Mount Mazama. The 

 lava surfaces exposed beneath the glacial till were well striated in a 

 N. 32° E. direction. 



Pimhice Drive (9). — A short distance northeast of Pumice Point 

 and 75 feet below the level of the highway is a layer of till 5 feet or 

 more in thickness, containing many well-striated stones, some of 

 them as much as 2 feet in diameter. The lava beneath the glacial 

 material is so weathered that all record of striae has been long since 

 destroyed. Above the till are 30 feet of stratified pumice followed by 

 iO to 15 feet of lava breccia and 30 feet of pumice. The conditions 

 here suggest that considerable eruption followed the last glacial 

 advance in this locality. 



The Wineglass (10). — North of Cloudcap and east of the Palisades 

 is an interesting feature known as the Wineglass. Viewed from the 

 lake, the white talus material appears like a huge goblet, the con- 

 stricted portion at the base of the bowl being produced by a resistant 

 layer of columnar lava. Resting on this columnar lava is a deposit 

 of glacial till consisting of a variety of volcanic rocks, many of them 

 subangular and striated. Many of the larger stones are 2 feet in 

 diameter. Above the till are approximately 20 feet of pumice fol- 

 lowed by 10 to 15 feet of lava breccia and 25 feet of pumice. Bedrock 

 striae were not observed at this locality, 



Skell Head (11). — A short distance from the rim road northeast 

 of Skell Head a thin deposit of glacial till rests upon striated bed- 

 rock. The till contains nicely rounded and striated stones, some of 

 which suggest the work of water as well as of ice. Compass readings 

 indicate that the ice moved in a N. 50° E. direction across the bed- 

 rock surface. 



Clovdcap (12). — On the rim directly west of Cloudcap is a layer 

 of pumice and fragmental material well over 100 feet in thickness 

 resting upon a striated lava surface. Owing to the inaccessibility of 

 the bedrock exposures and the advanced stage of weathering, only 

 two striae readings were recorded, both indicating a N. 70° W. direc- 

 tion. Unlike most localities thus far discussed no layer of dis- 

 tinctly glacial material was found. Numerous subangular stones 

 suggest that at least a portion of the fragmental material overlying 

 the glacial surface was transported by ice. 



S&ntinel Rock (13). — ^A mile to the southwest of Cloudcap is 

 Sentinel Rock, a promontory readily recognized from almost all out- 

 look points on the rim. Here a resistant lava formation is buried 

 under layers of pumice and fragmental material. In 1931 excellent 



