634 J BARLEN BRETZ 



In Washtucna Coulee, numerous prominent rock terraces from 

 150 to 200 feet above the present floor are probably remnants of 

 the earlier valley bottom. In Esquatzel Coulee, into which Wash- 

 tucna opens, these terraces are 200 feet and more above the bottom. 



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Fig. 9. — The lower part of Moses Coulee. Part of Malaga, Washington, topo- 

 graphic map. Note truncated spurs, hanging ravines, alluvial fans, and the great 

 terrace in both Moses Coulee and Columbia Valley. 



In Lower Moses Coulee (Fig. 9), the mouths of preglacial trib- 

 utary ravines hang approximately 400 feet above the rock floor. 

 Some of this discordance of grade is due to widening of the pre- 

 glacial coulee, which here was a canyon, by the glacial stream but 

 probably most of it is due to deepening during the glacial epoch. 



