256 HOWE & CROSS GLACIAL PHENOMENA, SAN JUAN MOUNTAINS 



mile above Durango and 12 miles below the mouth of the canyon proper. 

 Plates 30 and 31 represent these moraines in their relation to the gravel 

 terraces to be mentioned in another paragraph. The crests of these 

 moraines are not much more than 100 feet above the river, and are 

 separated by a shallow depression. The Animas has cut a channel through 

 the moraines on the extreme western side of the bottom land. 



It seems remarkable that so large a glacier as the Animas, and one 

 more than twice as long as that occupying the Uncompahgre valley, 

 should have left so small a terminal moraine. A reason for this is given 

 in a later paragraph. 



The most extensive recent glaciation on the western side of the San 

 Juan was in the various branches of the San Miguel river, within the 

 Telluride quadrangle. While there are in this region many typical 

 glacial cirques and evidence of ice-streams in the deeper valle}'s is abun- 

 dant, there are no extensive unmodified morainal deposits corresponding 

 to those of the Animas and Uncompahgre valleys. The principal boulder 

 and gravel masses exhibit marked water action. About Trout lake> on 

 the South or Lake fork of the San Miguel, there is much morainal 

 material, a part of which has been greatly disturbed by landslides. Some 

 discussion of the water-worn and water-sorted gravels of the glacial stage 

 is given in the Telluride folio. 



LATERAL MORAINES 



The lateral moraines of the glaciers described are, as a rule, not con- 

 spicuous features of the topography. They are, perhaps, more prominent 

 in the Animas valley than in the Uncompahgre, and this fact may 

 account in part for the smaller size of the Animas moraine, a greater 

 relative portion of the glacier's load having been deposited on the valley 

 sides than was the case with the Uncompahgre glacier. In this connection 

 may be mentioned the distributary stream from the Animas glacier, which 

 crossed the low divide on the western side at the head of the East 

 fork of Hermosa creek and descended that valley for 6 miles, depositing 

 notable moraines in the neighborhood of Hermosa park. In this way the 

 greater part of the load supplied to the Animas glacier by the tributary 

 from Cascade creek was diverted from Animas valley. 



Pronounced lateral moraines occur intermittently on both sides of 

 Animas valley from the terminal moraine to points overlooking the 

 canyon of the Animas above Canyon creek on the east and on the slopes 

 of Engineer mountain on the west. North of these points considerable 

 drift occurs, but it is more in the nature of terminal moraine left by small 

 tributary glaciers of the Animas,- while some may represent ground 



