146 C. W. Hayes — Expedition through the Yukon Distinct. 



have been concealed from us by the clouds which hung about 

 their summits. 



Recent volcanic Activity. 



The most striking effect of recent volcanic activity in this 

 region is the wide-spread deposit of volcanic ash, or tufa, which 

 covers the southeastern portion of the Yukon basin. This 

 deposit was first noted by Schwatka in his reconnaissance of 

 1883. It was more fully described as it occurs on the Pelly and 

 Lewes by Dawson in his report of the Yukon exiDcdition of 

 1886, and was noted by McConnell in 1887 and Russell in 1889 

 on the Yukon and Lewes. 



It was first seen by our party on Teslin river shortly after 

 leaving lake Ahklen, and from this point northward it forms a 

 conspicuous and nearly continuous white band in cut banks 

 of the river nearly doAvn to Selkirk, at the confluence of the 

 Lewes and Pelly. Where first seen the layer of tufa was less 

 than an inch in thickness, and from this increased to a maxi- 

 mum of nearly a foot near the mouth of the Teslin, with some 

 local accumulations of two or three feet. The alluvium which 

 has accumulated upon the layer of tufa is generally about a foot 

 in depth, but it occasionally varies -from nothing to three or 

 four feet. A foot, however, probably represents the normal 

 accumulation of soil under the prevailing conditions since the 

 deposit of the tufa. 



The first point at which the tufa was noticed in the White 

 River basin was about one hundred miles southwest of Sel- 

 kirk, on the divide between the Msling and Donjek, eastern 

 tributaries of White river. It is altogether probable that the 

 deposit was continuous over the whole of this country, but ho 

 localities favorable for its preservation and display were seen on 

 the high land traversed. A layer much heavier than that ap- 

 pearing on the LeAves would in a short time be wholly lost on a 

 surface almost entirely destitute of soil and composed of rock 

 fragments of varying degrees of coarseness. 



In the banks of the Kluantu and Donjek the tufa does not 

 form a distinct layer as along the Lewes, but is probably repre- 

 sented liy certain stratified beds of white sand, which were re- 

 garded at the time as lake deposits. They are indistinguishable 

 from the sediments carried and deposited by the river at the 

 present time, except in being somewhat coarser. 



