MAKVLNE.] GEOLOGY VALLEY OF THE UPPER GRAND. 159 



into the flatter valley, the bottom becomes a swampy, grassy meadow, 

 between one and two miles broad. Some pretending gneissic masses show 

 roche-moutonee forms. This meadow has a semicircular border at the 

 south, where it is limited by a not very prominent, but well-defined termi- 

 nal moraine, a a, (see figure.) Below this is a great mass of morainal 

 matter, h, with a well-defined southeastern border, c c, indicating a medial 

 moraine lying between the glacier which occupied the main valley, and 

 that from the Grand Lake cafions. The northern part of c, and the main 

 portions of the mass &, are thrown into piles and ridges reaching altitudes 

 probably 300 or 400 feet above the meadows. Its surface is exceedingly 

 uneven, abrupt depressions, perhaps 60 feet in depth, existing here and 

 there with no outlet, while the general tendency of the ridges is across the 

 valley in semicircular forms, marking the stoppages and accumulation 

 of the material from the surface of the slowly-retiring glacier. Several 

 small meadows are scattered in the lower portions of this mass. The trib- 

 utary canons of Grand Lake also contain, I am informed by Major Powell, 

 equally strong evidences of glacier occupation, both in their erosion and 

 morainal debris. A snaall terminal incloses the lower end of Grand 

 Lake, while the lake itself, though" not well Examined, gave the impres- 

 sion of occupying a true rock basin of deep ice erosion. From the 

 west end of the spur just south of the lake an exceedingly well-defined 

 lateral moraine {d) commences, and extends southward nearly two 

 miles. Though probably over 800 feet high where it leaves the spur, 

 it falls uniformly and evenly to its end. The southern end of ridge c is 

 low but well defined. The ]N"orth Fork cuts through it in a curious man- 

 ner, bending back northward to run along the upper side of the termi- 

 nal moraine, (e e;) also a low but well-marked ridge, through the eastern 

 end of which the united streams pass. Below is a meadow, limited 

 likewise on the south by still another but more prominent terminal 

 moraine, (//.) The eastern end of the latter moraine rests against a 

 granite mass, while a small meadow lies below its adjacent portions. 

 The upper end is rather confused with smaller side moraines. The cen- 

 tral portion merges almost imperceptibly into the irregular morainal 

 mass, (g,) which rises in low rolling hills and indefinite border from the 

 flat terraced, sage-brush valley m at the south. 



All these morainal masses are covered with a scanty soil and a thick 

 growth of pines. The latter have been blown down in all directions, 

 often in great broad swaths, and as often partially burned, rendering 

 passing directly across the moraines, without resorting to the little open, 

 marshy meadows, all but impossible. 



Good exposures of their rocky contents are not numerous. So far as 

 observed the boulders seldom retain well-preserved scratches, much 

 surface disintegration having taken place. Indeed, such is the general 

 rule with all tlae glaciated rock masses of the Eocky Mountains. The 

 roclw-moutonee form is frequent, but the schists and granites succumb 

 early to surface disintegration, and there has not been, as at the East, a 

 boulder clay or tuff to preserve them from weathering. It is rather a 

 curious feature that the Grand, instead of passing through the lower 

 portion of the valley occupied by the morainal mass, (g,) has cut a caGon 

 through the higher rolling spur of hard archcean rocks, {h.) 



The East Fork of the Grand commences as a well-defined open gorge 

 at the base of Arapaho Peak, and running about north 25^ east for 

 nearly six miles, it gradually swings around to a nearly westward course 

 near its mouth. Throughout this course this valley is exceedingly well 

 defined. The tendency is to a U rather than a V form, indicating, as 

 well as the usual scoring of the rocks, its glacial origin. The massive 



