46 



sufficiently. But it raaj be added that the relatively small scale map 

 with contours no closer than 200 feet (60 metersj is much less 

 convincing than an examination of the ground itself. I venture to 

 assert that no one who had made field observations would have 

 suggested the possibility of a flow from Katmai taking the course 

 outlined by Dr. Eschkr. The arrows on his map would make out 

 that a part of the flow turned out of the direct course and climbed 

 the 150 meter slope lietween Falling Mountain and Trident, instead 

 of continuing in a straight line down the Valley. Not only gravity 

 but also inertia acting as centrifugal force, would have opposed any 

 such course. The presence of the flow in the saddle of Katmai Pass 

 and down the slopes on both sides constitutes inescapable proof that 

 part of it originated near the divide. A good-sized crater which 

 may have been one of the points of origin lies in fact near the 

 summit of the pass. 



Any one of these three lines of evidence alone would negative 

 the possibility of our flow being a lahar of the Klut type. Taken 

 together they put such a hypothesis entirely out of the question. 



But, if the evidence definitely shows that our flow is not ana- 

 lagous with the hot lahars of Klut, the determination of its real 

 nature is quite another question. 



In our earlier studies, recognizing the evident resemblance of the 

 terrane to an ordinary mud flow, we sought to interpret it without 

 assigning a very high temperature to its material . — hence the 

 descriptive name applied, "iiot mud flow". It was recognized from the 

 first, however, that no ordinary aqueous suspension could ever 

 convert a whole forest into charcoal. Further study made it more 

 and more clear that the mass must originally have been very hot. 

 Charred wood occurs only near the foot of the flow, fifteen kilo- 

 meters or more from Novarupts. Throughout the main part of the 

 Valley the vegetation was entirely consumed and its ashes dissipated. 

 The rock of a whole mountain, named "Baked Mountain", was 

 changed from gray-green to brick red — as though subjected to a 

 high temperature for a prolonged period. 



The stiffened tuff left behind after the sand flow had come to 

 rest differs materially in several respects from the deposits of Klut. 

 In the first place it was much more viscous while in action. The 

 average thickness of the Klut lahar is estimated as only 50 centi- 

 meters. The pictures of destruction in Blitar all show a relatively 

 thin veneer of volcanic debris covering the ground. This terminal 

 portion moreover was not very hot as is evidenced by numerous 

 plants with unwithered leaves standing close to the volcanic debris, 



