MOVEMENTS AND DEFORMATIONS 351 



rock surfaces may perhaps be memorials of ancient earthquake 

 shocks: 1 



Changes of level. Permanent changes of level sometimes 

 accompany an earthquake. Thus after the earthquake of 1822 

 "the coast of Chili for a long distance was said to have risen 3 or 

 4 feet." 2 Similar results have occurred on the same coast at other 

 times, and on other coasts at various times. Depression of the 

 surface is perhaps even more common than elevation. Thus on the 

 coast of India all except the higher parts of an area 60 square miles 

 in extent were sunk below the sea during an earthquake in 1762. 

 Widespread depression in the vicinity of the Mississippi in Missouri, 

 Arkansas, Kentucky, and Tennessee accompanied the earthquakes 

 of 1811 and 1812. Some of the depressed areas were converted 

 into marshes, while others became the sites of permanent lakes. 

 Reelfoot Lake, mainly in Tennessee, is an example. Change of 

 level is often involved in faulting, and faulting is probably rather 

 common in connection with earthquakes. 



Changes of level are not confined to the land. Where earth- 

 quake disturbances affect the sea-bottom in regions of telegraph 

 cables, the cables are often broken. In such cases notable changes 

 have sometimes been discovered and recorded when the cables 

 were repaired. In one instance (1873) the repairing vessel off the 

 coast of Greece 3 found about 2,000 feet of water where about 1,400 

 feet existed when the cable was laid. In another instance (1878) 

 the bottom was so " irregular and uneven for a distance of about 

 two miles, that a detour was made and the cable lengthened by 

 five or six miles." In still another case (1885) the repairing vessel 

 found a " difference of 1,500 feet between the bow and stern sound- 

 ings." These records point to sea-bottom faulting on a large 

 scale. 



SECULAR MOVEMENTS 



The minute and momentary oscillations of earthquakes are very 

 unlike the slow movements of continents or ocean basins, or even 



1 Geikie, Text-book of Geology, 4th ed., p. 375. 



2 Ibid., p. 376. 



3 Forster, Seismology, 1877. Summarized in Am. Geol., Vol. Ill, 1889, 

 p. 182. 



