6o6 CLARENCE N. FENNER 



here, and the results of similar processes around the vents of the 

 fumaroles in the valley were observable. It is suggested that the 

 properties of the evolved gases indicated by this gaseous transfer 

 may at times lead to results of great importance in volcanic processes. 



A study has been made to determine the manner in which the 

 top of Mount Katmai disappeared and the great crater pit was 

 formed. It seems quite certain that the material was not blown 

 out directly but must be accounted for otherwise. Crater sub- 

 sidence may have been a factor, but it is believed that collapse of 

 the crater walls and incorporation of the material in the new magma 

 were chief features. It is recognized that the latter process 

 demands a large quantity of heat for its accomplishment, and the 

 magma evidently was not at a very high temperature prior to 

 its ascent; therefore accessions of heat seem to be demanded. A 

 considerable problem is thus presented, but it does not seem at all 

 insuperable, and it is believed that the evidences of solution are 

 so strong that they cannot be disregarded. 



One of the important features of the eruption brings up for 

 consideration a phenomenon to whose significance little attention 

 seems to have been paid hitherto. It is that of a gas-charged 

 magma gradually developing the explosive condition after some 

 interval has elapsed subsequent to its ascent from the depths. 

 The Katmai magma seems to have followed this course, and the 

 phenomenon is apparently not uncommon. This is believed to 

 have great significance and to imply changes of physical environ- 

 ment during its ascent, effected with such rapidity that internal 

 readjustments were not able to keep pace with them. Many of 

 the current theories of volcanism are based upon a fundamentally 

 different conception of the nature and properties of the magma. 

 It is thought that it may be advantageous in many cases to con- 

 sider matters from the new standpoint here suggested. 



In other matters also, theories that have been proposed and 

 somewhat widely accepted are apparently not in accord with the 

 evidence found here. It has not been possible in this article to 

 discuss these matters exhaustively, and other matters of interest 

 have not been touched upon. Fuller treatment will be presented 

 in articles to follow. 



July, 1920 



