Dec., 1918] The Great Hot Mud Flow 123 



not precisely level like the shore of a lake, but is subject to 

 variations in level so large as to be easily discernible to the eye 

 without the use of instruments; as though the Valley had been 

 filled with a heavy, viscous fluid like tar, which, as it flowed down 

 the Valley, had succeeded only imperfectly in finding its level. 

 The most conspicuous example of this is in the southwest corner 

 of the Valley under the glaciers of Mageik, where the "high 

 water rnark" is more than a hundred feet lower than further 

 east along the foot of Mount Cerberus. But the same departure 

 from a precise level appears in many other places. (See pages 

 121, 130 and 136). 



All around the margin of the Valley, just below the "high 

 water mark," runs a series of gaping fissures, as though the 

 surface had been stretched by subsidence after its formation. 

 Conditions remind one of a temporary puddle which, after having 

 frozen over heavily during a rise in a river, is drained again so as 

 to let the ice down onto the bottom with consequent stretching 

 and cracking all along the shore. The analogy is carried further 

 by the criss-cross cracks, which run in all directions across the 

 surface like the contraction cracks in a frozen pond. (See 

 page 108). Where the ridges from the shoulders of the mountains 

 project into the Valley, the marginal fissures coalesce and run 

 far out into the Valley in just such a Y form as do the ice cracks 

 at the point ot a peninsula in our drained pond. In another 

 place, where there was apparently a considerable detached 

 hill in the floor of the original valley, there remains a high area 

 whose crest is occupied by a notable fissure, just such as occurs 

 when the ice is let down over a similar hump in the bottom of a 

 pond. (See page 122). 



About ten miles down the Valley there is a distinct, horizontal 

 line of the same red material a hundred feet above the present 

 "high water mark," just as though the liquid that filled the 

 Valley, standing for a little while at this higher level, had 

 "frozen" a little along the bank before subsiding. 



The reader may perhaps wonder by this time why, when 

 there were such clear indications that this was a mud flow, we 

 had any hesitancy in calling it such at. once. But to us, as we 

 worked in the field, the reason was evident enough. By no 

 hypothesis that we could invent were we able to suggest a source 

 of the material. 



