576 CLARENCE N. FENNER 



recent eruption are likewise of this composition, as are also the 

 materials composing the bowlder beds at the rim of the crater 

 (which probably represent a ground moraine whose components 

 were transported by glaciers from the now annihilated upper slopes 

 of the mountain). The testimony from all sources is concord- 

 ant and demonstrates with a reasonable degree of certainty that 

 Katmai is predominantly andesitic throughout. 



In addition to the lavas that have built up these cones, however, 

 there seem to have been other products thrown out by them. In 

 several places near the lower end of the Valley of Ten Thousand 

 Smokes recent stream-cuttings show peat beds interstratified with 

 many narrow bands of siliceous pumice. Probably the rhyoiitic 

 lava ejected in the latest eruption of Katmai was not the first 

 highly siliceous differentiate evolved from the underlying magma. 



THE VALLEY OF TEN THOUSAND SMOKES AND ITS GREAT ASH DEPOSIT 



According to Spurr's description the portion of the Katmai 

 trail immediately to the northwest of the Pass ran for several 

 miles through a wooded valley of varied topography. During the 

 activities of the eruption, the floor of this valley was covered with 

 a thick deposit of ash and pumice, which in most places has buried 

 every detail of the former topography, and whose surface now 

 forms a gently sloping plain. Thousands of fumaroles have found 

 vent through this deposit and are sending out exhalations of hot 

 gases and vapors. Professor Griggs, who discovered and described 

 these remarkable features, has given to this valley the name 

 "Valley of Ten Thousand Smokes" (Figs. 6 and 7). 



This ashy deposit covers the old floor of the valley to a great 

 depth (possibly several hundred feet in certain areas) and extends 

 up over Katmai Pass. Its distribution is shown on the map of 

 the valley. 



From the very first explorations of the region by the National 

 Geographic expeditions. Professor Griggs recognized that this 

 deposit is quite distinct from the widespread ash-falls due to the 

 explosive ejection of material from Katmai crater, and that it 

 must be accounted for by the operation of other processes. Because 

 of the fact that, when first discovered, certain of its characteristics 



