Jan., 1919] Effects of the Eruption on Vegetation 177 



The present condition of the vegetation throughout this 

 zone is shown by the pictures on page 178. The trees and bushes 

 are dead or, toward the edge of the zone and in somewhat 

 sheltered places, have here and there a tuft of leaves where a 

 bud survived. Beneath the trees the ground is covered with a 

 rank growth of herbage. The effect of the ashfall here was the 

 same as at Kodiak — namely, to destroy the weaker plants, 

 giving increased opportunity for the strong growing survivals. 



Along the west side of Katmai Valley where the ashfall was 

 from 6 to 12 inches, the present herbage is an almost pure stand 

 of grass — Calamagrostis langsdorfii. In the Valley of Martin 

 Creek, which was much more lightly covered with ash, there is a 

 considerable variety of other plants beside the grass. In Ukak 

 Valley, where the ashfall exceeded a foot, all these were killed 

 and the present ground cover is horsetail — Equisetum arvense. 

 This plant grows, here in a luxuriance quite unmatched else- 

 where, covering mile on mile of country in pure stand. The 

 plants reach a size about double that usually attained by this 

 species, being fully waist high over large areas. (See page 178.) 



The matter of greatest interest to be discussed in connection 

 with this zone is, however, the cause of the death of the trees. 



WERE THERE HOT BLASTS IN THE ERUPTION? 



It is clear enough on the face of it that the death of these 

 trees cannot be accounted for by the ashfall. Over much of 

 this zone the ashfall is six inches or less, as compared with a foot 

 at Kodiak where the trees were not perceptibly injured. 



In view of this situation our first inquiry was as to whether 

 Katmai had given forth such hot blasts as characterized many 

 other eruptions, notably those of Pelee and Taal. It may be 

 stated very positively that there is no evidence whatever of any 

 blasts of such tornadic .violence as have occurred in many cases. 

 No uprooted trees or other similar evidence of high winds radiat- 

 ing from the crater are to be found. The absence of evidence does 

 not, however, furnish conclusive proof that such blasts did 

 not occur. 



The havoc wrought by other agencies was quite sufficient 

 to*cover up evidence of tornadoes of hot gas, which in a lesser 

 eruption would have left tremendous devastation in their wake. 

 The ashfall around the crater of Taal, for example, is reported as 



