68 



EARTH FEATURES AND THEIR MEANING 



Earthquakes are the sensible manifestations of changes in level 

 or of lateral adjustments of portions of the continents, and the 

 seismic disturbances upon the sea seaquakes and seismic sea 

 waves relate to similar changes upon the floor of the ocean. 



During the grander or catastrophic earthquakes, the changes 

 are indeed terrifying, and have usually been accompanied by losses 

 to life and property, which are only to be compared with those of 

 great conflagrations or of inundations on thickly populated plains. 

 The conflagration has all too frequently been an aftermath of 

 the great historic earthquakes. The earthquake of December 28, 

 1908, in southern Italy, destroyed almost the entire population of 

 a great city, and left of its massive buildings only a confused heap 

 of rubble (Fig. 49). Two years later a heavy earthquake resulted 

 in great damage to cities in Costa Rica (Fig. 50), while two years 



FIG. 50. Ruins of the Carnegie Palace of Peace at Cartago, Costa Rica, de- 

 stroyed when almost completed by the great earthquake of May 4, 1910 (after 

 a photograph by Rear-Admiral Singer, U.S.N.). 



earlier our own country was first really awakened to the danger 

 in which it stands from these convulsive earth throes; though, as 

 we shall see, these dangers can be largely met through proper 

 methods of construction. 



Earthquakes are usually preceded for a brief instant by sub- 

 terranean rumblings whose intensity appears to bear no relation 

 to the shocks which follow. The ground then rocks in wavelike 



