Dec., 1918] The Great Hot Mud Flow 125 



narrow gulch at the foot of the mountain. Material from a 

 large area was thus gathered together into relatively restricted 

 compass, forming a notable deposit many feet in thickness and 

 over two miles long. Although there were no eye witnesses 

 of the Katmai Mud Flow, there is the best of proof that it 

 occurred after the eruption, and probably in the manner stated, 

 for the tipper slopes of Katmai are still plastered with mud like 

 that which slumped off, and the mud flowed down over the 

 stratified ash, which is everywhere found beneath the mud 

 flow, showing clearly that the latter occurred after the ashfall. 

 (See page 124). 



But in the Valley of Ten Thousand Smokes conditions are 

 reversed, for the great mass of tuff which forms its floor is 

 everywhere overlain by the stratified ash from Katmai, (see 

 pages 110, 118, 120, 132, 136 and 140), proving that it must have 

 been in position at the time of the ashfall. When it was realized 

 that the great mass of tuff in the Valley had originated before the 

 ashfall, its interpretation became more of a puzzle than ever, 

 for everything indicated that it was no ancient formation, but 

 belonged to the present eruption. Mud flows of the type of 

 that formed on Mt. Katmai have frequently occurred after 

 eruptions, but nothing like this, occurring as a preliminary to an 

 eruption, is described in the literature with which we are 

 familiar. 



TUFF OF THE VALLEY HAS NO COUNTERPART ON THE 

 SURROUNDING MOUNTAINS. 



In view of these anomalous conditions, we felt that to adopt 

 the hypothesis that the tuff of the Valley was a mud flow would 

 raise more problems than it would solve. Such a supposition 

 appeared, therefore, of little value in interpreting the Valley. 

 We were left for a long while, therefore, without any hypothesis 

 whatever to account for what we saw. 



Nevertheless, detailed examination of the surrounding 

 mountains confirmed the suggestion of the ' ' high water mark ' ' 

 that the tuff was confined to the floor of the Valley for it had 

 absolutely no counterpart on the slopes above. They were 

 everywhere clothed with the same strata of ash as covered the 

 tuff itself. This stratified ash always rested directly on the 

 original surface of the ground bed rock or old soil as the case 

 might be, without the slightest indication of anything cor- 

 responding to the massive deposit in the Valley. 



