"SLIDES" IN THE CONEMAUGH FORMATION 



347 



feet in length, but rarely more than thirty feet in width. (Succes- 

 sive breaks in a slide mass often result in a series of small terraces 

 or steps which may be Hkened to step faults.) In some cases the 

 terraces are due to the position of a resistant rock ledge (Figs, i and 

 2). The overlying shales on this having been removed previously 



. .. '_.•? . '*«.. 



Fig. I. — Terrace at base of left-hand re-entrant as shown in next view. Slide 

 material has accumulated irregularly on a ledge of the Saltsburg sandstone (in Lower 

 Conemaugh), resulting in a general terrace form with lakelets of precarious life in 

 the hollows. 



either by sKdes or former river action, subsequent sKdes have 

 spread over the top and flattened to rough conformation with the 

 rock ledge. 



Sometimes slide material will accumulate at the base of a slope 

 in the form of a fan or cone, the accumulation probably being the 

 result of a combination of the sHde types. A hillside cut marking 

 the source of at least some of the slide material usually leads to it. 

 While these features are still fresh their origin can hardly be 

 questioned. With the passage of time the shde gullies may become 



