346 EARL R. SCHEFFEL 



or a lessened slope. If the obstacles are not sufficiently resistant, 

 they may be loosened and may also move forward. Slides of the 

 dry t5^e are frequently observable as an aftermath to the slide 

 movements of the first or second types, which are usually respon- 

 sible for the barren surfaces upon which the third t)rpe originate. 

 Generally the sliding mass is very small in bulk so that this type 

 is probably the least effective in total results. Inasmuch as all the 

 slides in these shales are primarily caused by water saturation, 

 these dry slides are merely secondary effects, tending to re-establish 

 the disturbed angle of repose. 



TOPOGRAPHIC FORMS PRODUCED BY SLIDES 



Several topographic forms have already been suggested, but it 

 was thought desirable to classify together those which simulate the 

 forms produced by other agencies. 



RESEMBLANCE TO GLACIAL FORMS 



The irregular surfaces produced by differential motion, especially 

 when the forward part of a slide or combination of sHdes is crowded 

 up, may give a gently pitted topography favoring the accumulation 

 of water in the depressions. The lakelets thus formed are rarely 

 permanent but may persist throughout the winter. These isolated 

 surfaces suggest modest morainic topography. Sometimes whole 

 hillsides are so cluttered with hummocks of slide masses that they 

 resemble mild kame and kettle areas upon a tilted base. The 

 scattered rock masses on hillsides, while usually more angular, 

 bring to mind the erratics of glaciated country. A hillside from 

 which much slide material has removed takes on a re-entrant 

 character similar to that produced by the plucking action of ice and 

 snow in a glacial cirque. Indeed as suggested by my colleague, 

 Professor Brown, the separation of the slide from the parent mass 

 resembles the bergschrund of a glacier. As bowlders from the 

 resistant formations are frequently mingled in haphazard fashion 

 with the clayey base, the heterogeneous character of glacial till is 

 produced. 



RESEMBLANCE TO DRAINAGE FORMS 



Upcrowded masses, when of considerable extent, frequently 

 resemble river terraces. These semblances may be hundreds of 



