290 PHYSICAL GEOLOGY 



marked for a distance of 43 miles and follows a system of long, 

 narrow valleys, except where it traverses wide valleys for short dis- 

 tances. In some places it passes over mountain ridges, sometimes 

 by a pass, but in some cases over the shoulder of a mountain. 

 _ ^ -^ * ~* Along the fault line low, precipitous 



""Z^^ . cliffs or scarps occur. Small basins or 

 ^=. ponds, many having no outlet, are of 

 fairly frequent occurrence and usually 

 lie at the base of the scarps. Trough- 

 like depressions bounded on both sides 

 by scarps also occur, and are due to 

 the subsidence of the ground or to an 

 uplift on one or both sides. In the 

 Japanese earthquake of 1891 the fault 



Diagram showing a line showed itself in some places as a 

 ridge formed above a fault plane. rid ag j f made b a gigantic mo l e 



(After Hobbs.) • I 11 / /£■ oo\ 



just beneath the surface (.big. 288). 



Sounds. — Accompanying or slightly preceding earthquakes, 



sounds, described as a hollow rumbling or grinding and sometimes as 



a roar, have often been noticed. These are produced by the breaking 



and grinding of the rock as it is thrown into vibrations, and by the 



falling and breaking of objects on the earth. 



Loss of Life. — The destruction of life is more impressive than any other effect of 

 an earthquake. In 1812 Caracas, Venezuela, was so severely shaken that 10,000 

 people were killed, while the loss of life in Lisbon in 1755 amounted to 30,000. In 

 1905 an earthquake in India (Kangra) destroyed 20,000 people, and it is estimated 

 that in 526 a.d. between 100,000 and 200,000 were killed by the shocks which dev- 

 astated the shores of the Mediterranean. In 1908 the Messina earthquake, described 

 as the world's most cruel earthquake, destroyed 77,283 people; and more than 30,000 

 were killed in the Italian earthquake of 1915. 



Fish in great numbers are sometimes killed by earthquake shocks which affect the 

 sea, lakes, or rivers. 



Effect on Underground Water. — After severe earthquakes it is not 

 unusual to find that some springs have become dry, that some have 

 had their volumes increased or decreased, and that some have burst 

 forth where none formerly existed. Along a fault rift which extends 

 for 120 miles in Afghanistan and Beluchistan over mountain and 

 valley, springs are found in abundance, the volumes of which are said 

 to be augmented after an earthquake disturbance. So marked is this 

 rift that it has long been utilized as a thoroughfare. The composi- 

 tion and temperature of the water of springs is also sometimes changed 



