"Rock Glaciers" or Chrystocrenes

Abstract

In number of Journal of Geology for June, 1910, there is an interesting article by Stephen R. Capps, Jr., on Rock Glaciers in which must be of especial interest to all those who have lived in Alaska or in Yukon Territory, and more particularly to those who have lived in city of Dawson, for these latter will at once recognize similarity of rockslides described and illustrated by Mr. Capps to the on face of Moosehide Mountain at north end of town of Dawson, since Slide is one of outstanding and ever-present features of landscape to every resident of that northern city. The city of Dawson is situated on a swampy alluvial flat on east bank of Yukon River, just below confluence of Klondike River. About a mile to northeast of it Moosehide Mountain rises to a height of 2,000 feet or more above city, a spur of mountain extending down to Yukon River, and terminating Dawson flat toward north. The mountain is composed of massive basic eruptive rock or diabase largely altered to serpentine, and cut by numerous jointage planes which allow rock to break readily into angular fragments. Over larger portions of surface of mountain rock has been weathered and decomposed to a considerable depth, and has broken down into sand or rock flour, so that natural slopes are consequently gradual and gentle. But on southwest side of mountain, directly overlooking town of Dawson, there is a steep scarped face of bare rock several hundred feet in height, at foot of which a talus of broken rock-fragments extends outward and downward toward river. This talus extends so far outward from foot of scarp, and its lower portion has such a relatively gentle slope, that it has somewhat appearance of having broken away suddenly from side of mountain; and consequently early