CHAPTER III. 



AEEA B— GEAND ElVEU VALLEY— EO AN OE BOOK CLIFFS- 

 LITTLE BOOK CLIFFS. 



As indicated in a previous chapter, Area B includes about 3,000 

 square miles. Of this, 1,100 represent Grand Eiver Valley. The en- 

 tire drainage of the area is tributary to Grand Eiver, which forms the 

 southern boundary. The northern boundary is the crest of the Eoan or 

 Book Cliffs. Almost all the area is a desert, and can be worked in detail 

 only in the spring or early summer months. It was visited by us in 

 the last week of September and the early part of October, when the 

 streams were dry. Salt Creek was the only one carrying water, and it 

 was a trickling stream of strongly alkaline water. The region between 

 the crest and the foot of the cliffs is also destitute of water except at a 

 few places. To be worked in detail it will have to be visited in the 

 spring; and the crest, along which an Indian trail takes its way, will 

 have to be the line from which it is worked. The cliffs are rugged and 

 precipitous, and considerable time will have to be spent in finding good 

 places to descend. Fortunately the geological structure is so simple 

 that a good idea of the areas occupied by the various formations was 

 obtained during our hasty trip along the crest, and no difficulty was ex- 

 perienced in coloring the geological map. The formations represented 

 are mainly Cretaceous and Tertiary, the outcrops of Jurassic and Tri- 

 assic being limited to a narrow belt along the course of Grand Eiver. 



GRAND RIVER VALLEY. 



Following the TJncompahgre Eiver northward, we find the broad val- 

 ley in which it is located extending northwestward along the Gunnison 

 and becoming the Grand Eiver Valley below the mouth of the Gunni- 

 son. It keeps a northwesterly course as far as Salt Creek. It then 

 curves around to the southwest, following the course of Grand Eiver, 

 which curves around the northern end of the Uncompahgre Plateau. 

 Beyond Muddy Creek the valley extends westward toward Green Eiver. 

 The total length of the valley following the general course of the river 

 is about 75 miles. Its width opposite the mouth of the Gunnison is 9 

 miles. On Salt Creek it is 15 miles, and on Muddy Creek about 20 miles. 

 The valley is nearly flat, there being a slight slope from the foot of the 

 cliffs toward the river, and a still smaller slope toward the cliffs from 

 the edge of the low hogback ridge bordering the river. A line of sta- 

 tions was made on this ridge. The valley is for the most part a desert, 

 covered with a sparse growth of stunted sage-brush, which grows in a 

 stiff alkaline soil made from the debris that is washed from the Book 

 Cliffs. Along Grand Eiver in the bottom-land there are groves of Cot- 

 tonwood. A portion of the valley between the Little Book Cliffs and Salt 

 Creek may be reclaimed by irrigation from Grand Eiver. Beyond Salt 

 Creek the level is too high above that of the river, which is in canon, 

 to be available for agricultural purposes by irrigation. West of Muddy 

 Creek the country rises into the divide between Grand and Green Elv- 

 ers. The streams flowing from the cliffs to Grand Eiver have cut deep 



170 



