Dec., 1918] The Great Hot Mud Flow 139 



the crater. Its glaciers are still, as Spurr described them, the 

 most extensive in the district. Two of them come down into 

 the Valley of Ten Thousand Smokes where their tips were 

 apparently melted by the mud flow as it ran across them, 

 but they show no sign of having otherwise contributed to it. 



If the eruption had caused any wholesale melting of glaciers, 

 not only should the bare hollows they formerly occupied be 

 evident, but the water thus released should have caused 

 tremendous floods on both sides of the range, for it is hardly 

 conceivable that all of the ice melted could have been in a 

 single locality, and that the whole of the water so formed could 

 have been taken up by the mud. But the only floods, of which 

 there is any evidence, occurred long after the eruption and 

 w r ere due to other causes. 



HOT MUD FLOW MUST HAVE COME FROM INTERIOR OF 

 THE EARTH. 



Although it has been made clear that the mud could not well 

 have come down from the mountains, one of the most important 

 evidences of that fact has not yet been discussed. The high mud 

 mark has been mentioned as one of the most conspicuous features 

 of the Valley. It was clearly produced, like a high water mark, 

 by the mud rising against the sides of the Valley. It would not be 

 developed at any point where mud flowed into the Valley from the 

 mountains above. It should, therefore, be easy to recognize the 

 source of the mud by the absence of high mud marks at any point 

 where it may have entered the Valley. But an examination of 

 the circumference of the mud flow shows that the high mud mark 

 is continuous, for it can be clearly followed around the whole of the 

 mud flow, except in the vicinity of Novarupta Volcano, where the 

 great thickness of the overlying ash deposit obscures the relation 

 of the deeper layers. This can only mean that the mud welled up 

 from within the Valley itself. (See map, page 138.) 



Our search for its source had to be transferred, therefore, 

 from the surrounding mountains to the Valley floor. The 

 broad smooth floor of the Valley, although broken by the 

 thousands of fissures and craters from which issue its millions 

 of volcanoes, shows no orifices that give any particular evidence 

 of having been the source of the mud. The only thing to guide 

 us in our search was the slope of the high mud marks, for since 

 the mud flowed down the valley under gravity it must have 

 originated, in part at least, near the highest points that it covered. 



