146 W. H. HOBBS REPEATING PATTERNS IN STRUCTURE OF LAND 



They have in part reduced the work of erosion; in part they have allowed 

 numberless dislocations to form which offered new points of attack to the 

 erosion." ... 



With little doubt the control of drainage lines exercised by gaping 

 joints within the rocks, is much facilitated wherever dislocation has in- 

 duced crushing upon any plane, or wherever the relief has been in any 

 way modified through actual displacement at the surface. 



Identity op many strong Lineaments with seismotectonic Lines 

 character of seismotectonic lines 



That lineaments are, in many cases at least, above the seats of recent 

 fault movement is indicated in their general correspondence with known 

 seismotectonic lines — the selective lines of heavy shock in connection with 

 earthquakes.^^ 



Seismotectonic lines are sometimes given a visible expression due to 

 the derangements of underground water-flow during an earthquake. The 



Figure 22. — Sand cones aligned along a Fissure 



This fissure opened at Moraza, in Servia, during an earthqualie wliich occurred on April 

 4, 1904. (After Micliailovitcli) 



fractures over which they lie become at such times the channels for ab- 

 normally large water currents carrying sand or mud from deeper lying 

 layers upward to the surface — they are much swollen, but ternporary fis- 

 sure springs. For the reason that the fractures are not uniformly gap- 

 ing, but appear to be enlarged wherever two or more series intersect, there 

 is a tendency for water-flow to be greatest at crossing points, which thus 

 become the loci of earthquake fountains and leave behind residual crater- 

 lets, sand cones, or mud volcanoes (see, for example, figure 22). 



Whenever the mud cones are so large as to make prominent features in 



2' W. H. Hobbs : On some principles of seismic geology. Gerland's Beitrage zur Geo- 

 physik, vol. 8, 1907, pp. 223-227. Earthquakes, an introduction to seismic geology. 

 New York, 1907, pp. 96-119. German translation of same. Leipsic, 1910, pp. 76-93. 



F, de Montessus de Ballore : La Science Seismologique. Paris, 1907, p. 449, fig. 164. 



