148 C. W. Hayes — Expedition through, the Yukon District. 



As described by Dawson * from the Yukon, " It is a fine, white, 

 sandy material * ^« * consisting chiefly of volcanic glass, 

 * >:« * the greater portion of which has been drawn out into 

 elongated shred§, frequently resembling the substance known as 

 ' Pele's hair.' " Where first noticed between the Nisling and 

 Kluantu it had the appearance of sand which results from the 

 disintegration of a rather coarsely crystalline marble, the indi- 

 vidual fragments being from 0.5 mm to 1 mm in diameter. The 

 average dimensions increase to the westward, and in the Klutlan 

 valley the deposit contains many fragments of white vesicular 

 pumice from two to ten centimeters in diameter, though the 

 greater part is much finer, perhaps from 1 mm to 5 mm in diam- 

 eter. Nothing in the nature of true volcanic bombs was seen in 

 the tufa, though their presence may have been overlooked. 



Taking the approximate limits of the deposit, as observed on 

 the Yukon by McConnell, on the Pelly and Lewes by Dawson, 

 and on the Teslin and at Scolai pass by the writer, it will be seen 

 to cover an oval area, with the maximum thickness near the 

 western extremity. The oval area (which is depicted on plate 

 18) is about 370 miles from east to west and 220 from north to 

 south, or about 52,280 square miles. Assuming the deposit to 

 be in the form of a flat cone with the above base and a vertical 

 height of but fifty feet, its volume amounts to 165 cubic miles of 

 material. 



From the facts of distribution, as above stated, a fairly safe 

 inference may be drawn as to the source of the deposit. The 

 explosive eruption which produced the tufa probably occurred 

 in the northern jjart of the St Elias mountains, near the source 

 of Klutlan glacier. As already stated, it was impossible to 

 tell whether there is any present volcanic activity in this region. 

 One conspicuous peak, of which the top remained hidden by 

 clouds, Avas pointed out by the natives as having some unusual 

 characteristics of which they seemed to stand much in awe. The 

 name by which they called the mountain was Nat-azh-at, mean- 

 ing, as near as I could make out, " shape of a man ; " but, owing 

 to native reticence and lack of an interpreter, it was impossible 

 to obtain any satisfactory information concerning the mountain. 

 Mount Wrangell has been suggested as the source of the tufa, 



* Report of an exploration in the Yukon district, N. W. T., and adja- 

 cent northern portions of British Columbia, 1887 ; Ann. Rep. Geol. Surv. 

 Canada, Montreal, 1889, p. 4f)B. 



