EXAMPLES OF SECOND-CYCLE FORMS 211 



A neighboring fault, studied by D. W. Johnson ('09, 148) and myself 

 ('01, 142), was found to be topographically obliterated for much of its 

 length, but it appears locally in obsequent and resequent scarps trans- 

 versely truncating several cuesta-like benches in the northward ascent 

 from the Arizona plateaus to the High plateaus of Utah. 



There can be little question that the recognition of the possible origin 

 of scarps along fault lines by erosion (fault-line scarps) as well as of 

 scarps by faulting (fault scarps) aids the determination of the class to 

 which a scarp belongs. The possession of an elaborated mental equip- 

 ment, including a good variety of type forms associated with faulted 

 structures, facilitates the detection of corresponding actual forms in the 

 field. The cases here considered, therefore, have a practical value as 

 part of the mental outfit of every observant student of land forms. 



An imaginary Example 



It is probably because of the unchanging constancy of the geological 

 elements of a fault that many descriptions of faulted districts made by 

 geological explorers are physiographically so unsatisfying. Indeed, one 

 sometimes reads even in geographical journals and under headings that 

 indicate the intention of the writer, whether he be a geologist or geog- 

 rapher, to produce a description of a landscape that he has traversed, 

 such a statement as the following: An important fault, with a displace- 

 ment of about a thousand feet, here brings Archean rocks and Triassic 

 beds against late Cretaceous strata. The failure to mention the strike of 

 the fault and the side of relative uplift is unsatisfactory even from a 

 geological standpoint, although the introduction of such terms as Ar- 

 chean, Triassic, and Cretaceous may give a geological reader some conso- 

 lation for other shortcomings. But the geographer is left entirely adrift 

 by such a description, particularly if it is not accompanied by an appro- 

 priate map or diagram; he can form no definite mental picture of the 

 landscape seen by the writer. The age of the faulted beds is of no use to 

 him, although it is unfortunately becoming habitual, especially in Ger- 

 many, to overload geographical descriptions with terms expressive of 

 geological dates. Such terms are, of course, of value in themselves ; they 

 arc useful in various scientific relations; they are essential in a geo- 

 logical history of a district; but, let it be repeated, they give no aid in 

 forming a mental picture of surface forms; hence they are of no value in 

 a purely geographical description. Whal a geographical reader does need 

 io know ;is to ihc rocks, in such an instance as is here considered, is nol 

 the ancient date of their formation, hut their preseni composition, atti- 



