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The Ohio Joiinial of Science [Vol. XIX, No. 2, 



before we came to its extremity, we had reached a distance of 

 20 miles (32 km.) from the point where we first encountered 

 it back of Observation Mountain, and 15 miles (24 km.) from 

 the divide back of Novarupta Volcano. Altogether it occupies 

 an area of 53 square miles (137 sq. km.). At its highest points, 

 on the divide back of Novarupta and in Katmai Pass, it reaches 

 an altitude of about 3,000 feet, while at the other extremity it 

 extends down to within about 300 feet of sea level. 



Photograph by J. D. Say re 



"HOODOO" NEAR FISSURE LAKE. 



Characteristic "Hoodoo" weathered out of the solidified mud near Fissure Lake. 



The stratified ash from Katmai lying on top of the massive mud flow 



is well shown at both right and left. 



Everywhere, in appearance and structure, this formation 

 closely resembles the Katmai mud flow. In color and character 

 the material of the two are of almost identical appearance, 

 being darker and finer than the other ejecta of the recent 

 eruption. They have the same total absence of stratification or 

 of horizontal cleavage planes, contrasting most strongly with 

 the thin beds of the stratified ash. Where cut into by erosion 

 or sheared by faulting, they break with irregular fractures 

 running in any direction with the line of stress. By reason of 

 the character of their cleavage, they are often broken or weath- 



