358 ELEMENTARY GEOLOGY 
Accompanying the shock there is often a change in the level 
of the land, either an uplift or a depression; and in such cases, 
fault-scarps, or cliffs are actually formed. This was particularly 
noticeable in the Japanese earthquake of 1891, in which a fault 
appeared at the surface of the earth for many miles (Figs. 170 
and 219). In other cases there have been irregular depressions 
in which lakes have gathered, as happened in the Mississippi 
valley during the violent earthquakes which devastated that 
region in the years 1811-1812. However, in many cases, these 
are not caused by the earthquake, but are rather accompanying 
phenomena, which perhaps represent the cause of the shock. 
Cause of Earthquakes. — In considering the cause of 
these jarrings of the earth, it is well to look first at the 
regions in which they are likely to occur. Places where 
earthquake shocks are frequent and violent, are usually 
either among mountains of recent or present growth, or 
else i the neighborhood of volcanoes. Yet shocks 
are apparently possible in any part of the earth. 
In this country, during the present century, we have 
had two shocks of some violence east of the Rocky 
Mountains, one at Charleston, South Carolina, the other 
in the Arkansas region of the Mississippi valley. Dur- 
ing the same time, in the much smaller area of Japan, 
there have been more than a score of shocks, each 
equalling or exceeding pur own in violence. Among 
the Cordilleras, also, there have been numerous jarrings 
of the earth, some assuming considerable intensity. 
Another noteworthy fact is that shocks appear to start 
from a plane, not from a point. It is significant, too, 
