84 



EARTH FEATURES AND THEIR MEANING 



trees. Areas where such spurting up of the water has been ob- 

 served have in most cases been shown to correspond to areas of 

 depression, and such areas have sometimes been left flooded with 

 water. During the Indian earthquake of 1819 an area of some 

 200 square miles suddenly sank and was transformed into a lake. 

 Sand or mud cones and craterlets. From a very moderate 

 depth below the surface to that of several miles, all pore spaces 



'&S$XSl^eettfa 



POROUS^ 



* ._ . r. . .. . '"I 



Swamp drained. 



FIG. 77. Diagram to illustrate the derangements of flow of water at the time of 

 an earthquake ; water issuing at the surface over downthrown rocks, and being 

 sucked down in upthrown blocks. 







and all larger openings within the rock are completely filled with 

 water, the " trunk lines " of whose circulation is by way of the 

 joints or along the bedding planes of the rocks. The principal 

 reservoirs, so to speak, of this water inclosed within the rock are 



FIG. 78. Mud cones aligned upon a fissure opened at Moraza, Servia, during 

 the earthquake of April 4, 1904 (after Michailovitch). 



the porous sand formations. When, now, during an earthquake a 

 block of the earth's shell is suddenly sunk and as suddenly arrested 



