TT.vnrvi GEOLOGY MOEAINAL DEPOSITS. 61 



in restricted localities by the outflow of igneous matter. Between East 

 Fork and the next branch a long ridge runs nearly west down toward 

 the Gunnison 1,200 to 1,500 feet above the stream. On the north side 

 of the valley of the east branch the dip is variable from 10° to 30°, 

 and trending toward the west and northwest. There is really here 

 a broad slope extending from Italian Peak to Teocolli, where the little 

 streams have carved out deep gorges through the red sandstones and 

 pudding-stones. The aggregate thickness here cannot be less than 

 2,500 feet, and it may be much more. The valleys or gorges have all 

 been formed by erosion, and from margin to margin they are usually 

 about a mile in width, sloping down more or less abruptly to the bottom, 

 where the immediate valley varies from 100 yards to one-fourth of a mile 

 in width. 



The texture of these red beds is very variable. Conglomerates vary- 

 ing from a fine pudding-stone to a coarse aggregate occur all through 

 the mass, but are not continuous. The entire group indicates deposition 

 in disturbed waters. In tracing abed horizontally sometimes it will 

 thicken to a massive fine sandstone, then gradually thin out, and in its 

 place* soft, yielding shales appear. Sometimes a bed will be a coarse 

 conglomerate, and in a short distance it will change into a fine sand- 

 stone or even soft sand loosely held together. The irregular laminae of 

 deposition and wave-marks are shown everywhere also, and the signs 

 of quiet waters are local and of comparatively short duration. The map, 

 when completed, will show a water-divide between the branches of the 

 Gunnison and those of the Blue, trending about northwest and south- 

 east, with Italian Peak at the southeast end, with Castle, Maroon, and 

 Black Pyramid along the line, and ending in Sopris Peak. The 

 numerous little branches will be seen extending down from this crest, 

 uniting to form the larger streams on either side. All these little 

 branches rise in broad amphitheaters which have been produced 

 for the most part by erosion or the slow process of wearing out in a 

 more or less circular or semicircular form by water and ice. 

 These amphitheaters are numberless and occur on both sides of 

 the crest. In many places the wearing out of the amphitheaters 

 on both sides has been such as to remove hundreds of feet of the crest, 

 thus forming a pass of greater or less elevation. In these amphithea- 

 ters vast bodies of snow accumulate during the winter, a portion of 

 which, in many instances, remains all the season. In the spring the 

 process of thawing and freezing commences, and the slow breaking down 

 of the amphitheater walls is continued. Thousands of little streams are 

 formed by the melting of the snow, and the water flows down to join 

 the main streams. 



All these great ranges of mountains are full of fissures, which, running 

 in various directions, break up the entire mass. We can find these 

 openings full of ice at almost any season of the year, and the well-known 

 power of ice by expansion need not be stated here. This action will 

 account for the vast quantities of debris all over the sides and sum- 

 mits of our mountain-ranges. The more prominent the range of 

 mountains the more conspicuous is this feature, and the debris 

 becomes most noticeable among all the great ranges of Colorado, 

 as well as Montana. The Sawatch, Park, and Elk ranges are excellent 

 illustrations of what I have attempted to describe above. From the 

 crest or divide between the branches of the Gunnison and the Blue 

 Elvers, the little branches have carved out deep valleys or gorges, nar- 

 row or wide, depending much upon the texture of the rocks through 

 which the stream has cat its way. Many of these valleys are covered 



