GEOLOGICAL ELEMENTS IN GEOGRAl'IIirAL DESCRIPTIONS Oo 



tains was marked off from that of tlie less uplifted plains on the east. 

 The forms of the highland shows that the whole region advanced far 

 through the cycle of erosion introduced by the monoclinal uplift, so that 

 the resistant underhing crystalline rocks of the mountain area were 

 stripped of their cover and worn down to a gently rolling peneplain, 

 diversified by irregularly scattered monadnocks, rising singly or in groups, 

 with a relief of from 500 to 2,500 feet, while the valleys of the highland 

 show that a renewed uplift gave the whole region a greater altitude than 

 before, with a gentle up-arching along a north-south axis in the mountain 

 area 15 or 20 miles west of the monocline, whereby the peneplain, with its 

 scattered monadnocks, gained the highland altitude of the present Front 

 Kange ; the crest of the up-arching and the monadnocks that happened to 

 lie near it defining in a general way the crest of the range, which here 

 constitutes the continental divide. The weaker strata of the plains are 

 now again worn down to small relief, but the harder crystalline rocks '^f 

 the mountainous highland are only submaturely dissected by normal sub- 

 mature or mature valleys, the higher parts of which have recently been 

 strongly glaciated. Thus ends the description. 



(GEOLOGICAL ELEMENTS IN GEOGRAPHICAL DESCRIPTIONS 



It is quite possible that many hearers ncJw present will regard this de- 

 scription as having at least a highly geological flavor, even if they do not 

 think it pure geology. Let us inquire, therefore, on what elements of the 

 description such an opinion may be based. First, I presume, on the men- 

 tion of certain kinds of rocks, namel}', disordered crystallines and strati- 

 fied sedimentaries ; second, on the mention of the structure given to these 

 rocks by uplift and deformation which took place in past ages ; third, on 

 the mention of erosional processes, glacial as well as normal, acting in the 

 past, and of the work that they have accomplished. Let us examine these 

 elements separately in the order just stated, with the object of learning 

 how far their presence determines the geological or the geographical 

 nature of a description that contains them. 



If the mention of rock composition determines that a description 

 should belong under geology instead of under geography, then such 

 phrases as the cross-bedded sandstones of the White cliffs in southern 

 Utah, the chalk cliffs of southeastern England, the basaltic columns of 

 the Giants causeway, the dolomite mountains of the TntoI, the sand dunes 

 of the Sahara, and so on, all belong in geology and not in geography; 

 nevertheless, such descriptions are often, and I think quite properly, 

 found in geographical literature. 



TJock attitude as well as rock composition may be mentioned, as in de- 



