THE KATMAI REGION, ALASKA 587 



outer surface. The most striking result is the deposition of iron 

 compounds around the vents and in the steamy areas — pyrite, 

 hematite, and magnetite — in quantities which, from the observa- 

 tions of Dr. Allen and Dr. Zies, must be very great in total amount. 

 When there is brought before us in such striking fashion evidence 

 of the ability of these volcanic gases to transport material, we are 

 naturally led to a consideration of the various circumstances 

 attending the evolution of such gases and the effects that are likely 

 to be accomplished. One query that arises is as to the results of 

 the continual outpouring of such great volumes of vapor as rise 

 from the neighboring peak,- Mount Martin, and we may ask 

 whether significant changes of composition are not thereby effected 

 in whatever material may lie at the source from which this vapor 

 proceeds, whether it be a body of magma or material of another 

 sort. Unfortunately, insufficient knowledge of the composition of 

 gases rising from the actual throat of a volcano, as well as of 

 their amount and the length of time over which their escape con- 

 tinues, involves the subject in so much uncertainty that definite 

 conclusions as to the quantitative importance of this process are, 

 as yet, hardly warranted. 



THE NEW VOLCANO NOVARUPTA 



Near the head of the Valley of Ten Thousand Smokes is the 

 site of Novarupta, a small parasitic vent, which evidently was an 

 exceedingly active volcano during the general eruption, and threw 

 out great quantities of fragmental material, chiefly pumice. Much 

 of this is in much larger masses than those thrown out by Katmai. 

 One such projectile, found about a quarter of a mile away, had a 

 diameter of eight feet. The last act of the vent was to extrude 

 a mass of stiff, viscous glass, which, as it was slowly thrust upward, 

 broke into huge blocks. From a distance this pile of steaming 

 lava-blocks, which is about 800 feet in diameter and 200 feet high, 

 resembles an enormous ash heap. It is surrounded by a circular 

 crater-wall composed of ejected fragments, which is much cut up 

 by actively steaming fissures (see Fig. 13). The material of this 

 is mostly pumice and obsidian, but there are also pieces of shale 

 and sandstone and of dense andesite. The question as to the 



