256 Hobbs — Features Formed at the Time of Earthquakes. 



formed as a result of derangements in the ground water system 

 during earthquakes, they are doubtless aligned upon fissures 

 and located where these fissures are widened — in the majority 

 of cases doubtless at fissure intersections. Such an alignment 

 has already been indicated by Fenneman, but has not been 

 worked out in detail. Their importance as points of segre- 

 gation of petroleum greatly adds to this interest and places 

 them at once in relation to the famous " mud volcanoes " of 

 Baku, the lineal alignment of which was long since indicated 

 by Daubree.* There is thus at least the possibility of gaining 

 some knowledge of the earth's fissure system beneath the 

 Gulf Plain notwithstanding its deep blanket of unconsolidated 

 material. 



University of Michigan, 



Arm Arbor, Michigan, January 22cl, 1907. 



*A. Daubree, Les eaux souterraines a l'epoqne actueile, A r ol. i, pp. 383- 

 385. 



