60 EDWARD M. SHEPARD 



earthquake district, which is also an artesian district, may have been 

 due to the long and slow undermining of superincumbent beds by 

 the removal of sand by artesian pressure. Visitors to this region 

 have informed the writer that large quantities of sand were thrown 

 up at various places during the shocks, and that springs bringing 

 up sand still issue from the fissures thus made, similar to those 

 described in the Big Bay district. 



COMPARISON WITH CONDITIONS NEAR SHREVEPORT, LA. 



Several visits to the region around Shreveport, made a number 

 of years ago, revealed a condition similar to those of the New Madrid 

 area, and suggested the probability of the agency of earthquakes in 

 producing the lakes, swamps, and deposits of sand so characteristic 

 of this portion of the state of Louisiana. Shreveport is likewise an 

 artesian region, and in its geological structure is similar to that of 

 New Madrid. Sunken lakes covering forests occur there, as described 

 by Lyell, 1 who calls attention to these sunken lakes as illustrating 

 the changes now in progress in the earth's crust. In the Red River 

 region of Louisiana he mentions Lake Bistineau, which is 30 miles in 

 length and from 15 to 20 feet deep, and on which one may float over 

 a submerged forest. He also refers to Black, Caddo, Spanish, and 

 Natchitoches Lakes, and does not agree with Darby's view that 

 the gradual elevation of the bed of the Red River by the accumula- 

 tion of alluvial material has raised its channel and caused its waters, 

 in flood time, to flow up the mouths of some of its tributaries and 

 to convert parts of their courses into lakes. Lyell says that — 



Most probably the causes assigned for the recent origin of these lakes are not the 

 only ones. Subterranean movements .... have altered the levels of various 

 parts of the basin of the Mississippi. 



Mr. A. C. Veatch says in a paper on the Shreveport area: 2 



The valley region above Shreveport is possibly unique in the respect that 

 changes, which usually occupy great periods of time, and whose full story can 

 only be learned by deduction, have taken place here within a few years. Lakes 

 have been formed and destroyed; streams formed and abandoned; waterfalls 

 produced to destroy themselves; new streams formed out of parts of the beds of 

 old ones; and temporary reversals of the drainage system have been effected. 



1 Lyell, Principles of Geology, VoJ. I, p. 457. 



2 Geological Survey of Louisiana, Report /or 1899, p. 152. 



