[TYRRELL] FROZEN MUCK IN THE KLONDIKE 41 



The sand and gravel so deposited and preserved on the alluvial 

 flats is now overlain by a deposit of vegetable material locally known 

 as "muck," which may have a thickness of ten, twenty, thirty, or even 

 as much asone hundred feet. The plane of separation between the gravel 

 and "muck" is usually sharp and well defined, though occasionally 

 little layers of "muck" may be found included in the upper beds of 

 the gravel. The general impression that a person gets from a study 

 of the deposits, however, is that of a sudden change from gravel to 

 "muck." 



"Muck" is composed very largely of vegetable material, in part 

 of mosses, such as Sphagnum and Hypnum, but also of sticks and limbs 

 of trees, leaves, and of all kinds of vegetable debris. It also contains a 

 large quantity of water in the form of ice, the percentage by weight 

 being on an average about 44% as determined by Mr. H. M. Payne 

 for the Yukon Gold Company.^ Incidentally it may be remarked 

 that this percentage is about the same as that in the green timber 

 growing on the adjoining hills at the present time. Here and there in 

 the muck are also layers of clear ice which have been formed by spring 

 water rising from beneath and freezing before it reached the surface. 

 In one instance which was examined the water derived from this ice 

 was found to be quite hard from the presence of salts of lime. Some 

 gritty material may also be present in the muck and occasionally 

 towards the bottom there may be a few thin layers of sand. 



In colour muck is usually dark blueish grey or brown, much like 

 the bottom turf in the Irish bogs, though it becomes lighter with the 

 presence of sand. On the und rained parts of alluvial flats it is now 

 generally covered with mossy swamp, while near the channels of 

 streams it supports a lusty growth of white spruce forest. 



At the present time it, and the gravel and rock underlying it, 

 are permanently frozen to depths of about two hundred feet down 

 below the surface. In mining operations shafts can readily be sunk 

 through it with pick and shovel, for an experienced man can pick it 

 ofif in layers without difficulty. But as soon as the underlying frozen 

 gravel is reached little or no impression can be made on this gravel with 

 a pick, and some process of thawing must be resorted to before it can be 

 extracted. When "muck" is thawed artificially it turns to a semi- 

 liquid mass, and much of it will flow away if given an opportunity. 



"Muck " is often spoken of as frozen bog. Much of it was undoubt- 

 edly bog, and bog-mosses such as Sphagnum and Hypnum constitute 

 a considerable part of it, therefore it is reasonable to infer that the 



'The Development and Problem of the Yukon, by H. M. Payne. Trans. Can. 

 Min. Inst. Vol. 16, 1913, pp. 228-240. 



