216 MOVEMENTS AND DEFORMATIONS 



i 



destructive. Such waves have been known to advance on the land 



as walls of water 60 feet high. They are most destructive on low 

 coasts where the water sweeps over great areas of land. Great 

 loss of life may be caused by such waves. 



Earthquake shocks are remarkably destructive to the life of 

 lakes and seas. Thus during the Indian earthquake of 1897, "fishes 

 were killed in myriads as by the explosion of a dynamite cartridge. 

 . . . and for days after the earthquake the river (Sumesari) was 

 choked with thousands of dead fish. . . . and two floating car- 

 casses of Gangetic dolphins were seen which had been killed by 

 the shock." 1 This wholesale destruction of life is of interest since 

 the surfaces of layers of rock, even of great age, are in some cases 

 covered with fossils in such numbers as to indicate that the ani- 

 mals were killed suddenly and in great numbers, and their bodies 

 quickly buried. It has been suggested that such rock surfaces 

 may perhaps record ancient earthquake shocks. 



Changes of level. Permanent changes of level accompany 

 some earthquakes. Thus after the earthquake of 1822 "the coast 

 of Chili for a long distance was said to have risen 3 or 4 feet." 

 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. Wide- 

 spread 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 involved in much of the faulting which goes with earth- 

 quakes. 



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

 quake disturbances affect the sea-bottom in regions of telegraph 

 cables, the cables may be broken. In some such cases notable 

 changes have been discovered when the cables were repaired. In 

 one instance (1873) the repairing vessel off the coast of Greece - 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 



1 Oldham, loc. cit., p. 80. 



2 Forster, Seismology. Summarized in Am. Geol., Vol. Ill, 1889, p. 182. 



