EARTHQUAKES AND GEYSERS 357 
ground dislodges rocks and even starts avalanches, thus 
furnishing an aid to weathering. Sometimes the shocks 
dam good-sized rivers by throwing down masses of earth. 
One of the most important effects is the production 
of an earthquake water wave, which is formed when 
the epicentrum is in or near the sea. This rushes with 
Fig. 218. 
Destruction of property during Japanese earthquake of 1891. 
fury upon the neighboring coasts, overwhelming every- 
thing in its path, and sometimes reaching 100 feet above 
the general water level. Fortunately this is destruc- 
tive only on the neighboring shores; but as a meas- 
urable wave of water, it may pass half way around the 
earth. Such waves, starting on the Asiatic coasts, have 
been measured on our western coast. 
