TOPOGRAPHY OF CENTRAL WYOMING 



broad as a rule; even in the case of small streams they may be 

 several miles wide. In these broad valleys the streams are 

 almost lost and they meander back and forth in the most devious 

 way, indicating that the streams have well nigh reached local 

 base level. The broad undissected terraces contribute much 

 to form the block-like topography of the plains region. In 

 addition to the stream terraces, there is also a series of terraces 

 at the foot of the mountains. In most cases these are made up 

 ol confluent fans, which stretch along at the base of the moun- 

 tains for miles, parallel to their trend and only occasionally 

 sending out a tongue of gravel into the plain beyond. The 

 terraces of this sort are composed of coarse gravel where they 

 join the mountains, but this becomes finer as the plain is 

 approached. 



The fronts of these terraces are often modified by stream 

 action. In such cases they possess steeper slopes than is other- 

 wise the case, for unless stream action has been present they pass 

 by gradual degrees into the plain. All of the terraces are modi- 

 fied more or less by subsequent drainage. It is interesting to 

 note how many of these drainage lines have originated. In 

 most instances they have been located by the old-time buffalo 

 trails and by the more modern catde trails. These anim.als 

 passed from their grazing grounds on the higher lands down 

 to the streams by fixed trails which became deeper and deeper 

 with constant use. It was not long before a deep trail became 

 a passageway for water and soon grew into a regular water way, 

 which soon developed into a permanent stream, or at least 

 became a draw or gully. These draws can be seen in all 

 stages of development, from the slightly eroded cattle trail to 

 the well-developed ravine. 



Basins : Perhaps no feature attracts the attention of the 

 geologist to a greater degree than the basins which abound on 



