366 EHRENFELD— JOINTING AS A FUNDAMENTAL FACTOR 



Society of America ; Hobbs* in a long series of papers has discussed 

 quite fully the subject of jointing in the relation to earth features 

 and surface conditions. I. D. Scott^ discusses joints and fracture 

 systems as effecting relief and control of drainage and gives also a 

 summary of the literature on the general topic of joints. One of the 

 surprising things about this literature in regard to joints is the almost 

 complete agreement among textbook writers in the comparative neg- 

 lect of jointing as a really important active factor in earth dynamics; 

 the subject of jointing is usually considered as a phase of structural 

 geology rather than as an active controlling agent in the behavior of 

 the lithosphere. This is, I believe, a serious neglect and a condition 

 of affairs which is totally unwarranted by the nature of the sub- 

 ject. One of the chief points I wish to emphasize in this discussion 

 is the proposition that earth fracturing is one of the essential active 

 fundamental geophysical constants akin to igneous agents in the 

 continuity of its action and the universality of its results, that it is 

 inherent in the nature of the lithosphere ; no portion of the world 

 as we know it to-day is free from the action of jointing and I be- 

 lieve it can ultimately be demonstrated and proved that this jointing 

 of the lithosphere has been active throughout the past geological 

 history as a general controlling factor in the great geographic and 

 paleographic changes shown by the records of historical geology. 

 Evolution of the lithosphere without the controlling influence of 

 jointing seems to me an impossible hypothesis. 



It may be worth while to classify into a few general groups the 

 manner in which jointing is now seen to be a controlling factor in 

 the changes occurring in the lithosphere ; among these groups may 

 be cited the following : 



(a) Repeating patterns of authors. 



(b) Control of river drainage. ^"^ 



(c) Coast lines.^^ 



s Details may be found in " Earth Features and their Meaning," New 

 York, 1912; "Earthquakes," New York, 1907; see especially Bull. Gcol. So- 

 ciety of America, Vol. 15, pp. 483-586. 



^ Gerlands, Bcitr. zur Geophysik., XIII. , 1914, pp. 163 ff. ; idem., pp. 241-260. 



10 Hobbs, " River Systems of Conn.," Journal Geology, Vol. IX., 1901, pp. 

 469-485. Iddings, ibid.. Vol. XIL, 1904, pp. 94-105. 



11 Hobbs, " Lineaments of the Atlantic Border Region," Bull. Gcol. Soc. 

 Amer., Vol. XV., pp. 483-506. 



