70 



EARTH FEATURES AND THEIR MEANING 



the water. The distribution of these shocks, as indicated either 

 by the experiences of neighboring ships at the time of a particular 

 shock, or by the records of vessels which at different times have 

 sailed over an area of frequent seismic disturbance, appears to be 



limited to narrow zones or lines (Fig. 

 53). The same tendency of under-sea 

 disturbances to be localized upon defi- 

 nite straight lines has been often illus- 

 trated by the behavior of deep-sea 

 cables which are laid in proximity to 

 one another and which have been 

 known to part simultaneously at points 



FIG. 53. -Map showing the lo- ' ran g ed U P On a Slight line. 



caiities at which shocks have Far grander disturbances upon the 

 been reported at sea off Cape fl oor o f the ocean have been revealed 



by the great sea waves - the so-called 



" tidal waves/' properly referred to as tsunamis which recur in 

 those sea districts which adjoin the special earthquake zones upon 

 the continents (p. 86) . The forerunner of such a sea wave approach- 



FIG. 54. Effect of a seismic water wave at Kamaishi, Japan, in 1896 (after E. R. 



Scidmore). 



ing the shore is usually a sudden withdrawal of the water so as to 

 lay bare a portion of the bottom, but this is well-recognized to be 

 the premonition of a gigantic oncoming wave which sweeps all before 

 it and is only halted when it has rolled over all the low-lying coun- 



