THE KATMAI REGION. ALASKA 



585 



in length. The velocity of the outpouring gases is seldom very 

 high; commonly their escape is attended by a hissing sound at 

 small vents and a subdued roaring at large ones. A close view of 

 a vent of moderate size is shown in Figure 12. It should not be 

 inferred that all of the water that is evolved is of magmatic origin. 

 The ashy and pumiceous material that forms the upper part of 



Fig. 12. — Fumarole No. 42. Baked Mountain and Broken Mountain in the 

 background, and the volcanic range in the far distance. Photograph by E. G.Zies, 1919. 



the conduits is soaked with water, and considerable quantities 

 must be vaporized and carried out with the hot gases. 



FALLING MOUNTAIN 



In the upper part of the valley and not far from Novarupta is 

 Falling Mountain, so called from certain remarkable phenomena 

 which it exhibits. Its northerly face is an almost cliff-like slope, 

 probably 2,000 feet in height, which has plainly been produced 

 by recent slumping off of masses of rock. The volume of material 

 thus removed must have been enormous. At the present time 

 blocks or small masses of rock drop off at short intervals and 

 plunge down the slopes with a succession of sharp crashes, and a 



