THE GREAT RELIEF FEATURES OF THE LAND 287 



result of the filling of a shallow sea border by wash from the 

 land. Great interior plains are either areas once high but 

 now worn low, or, oftener, they are former coastal plains 

 now separated from the sea by newer land. 



The surfaces of plains due to recent emergence are likely 

 to correspond approximately with the bedding planes of 

 the strata, and the rocks are usually poorly consolidated 

 (p. 37). The surfaces of peneplains developed on stratified 

 rocks, on the other hand, bevel the edges of beds without 

 regard to the dip, and the rocks below the mantle rock are 

 generally well consolidated. 



The changes produced on plains by erosion have been 

 discussed sufficiently in earlier chapters. 



REFERENCES 



DANA : On the Origin of Mountains, in Am. Jour. Sci., 3d Series, 



Vol. V, pp. 347-350, 423-443 ; Vol. VI, pp. 6-14, 104-115, 161- 



172. 

 DAVIS : The Ranges of the Great Basin, in Science, N. S., Vol. XIV, 



pp. 457-459. 

 The Mountain Ranges of the Great Basin, in Bull. Harvard 



Mus. of Comp. Zool., Vol. XLII, pp. 129-177. 

 An Excursion to the Plateau Province of Utah and Arizona, in 



Bull. Harvard Mus. of Comp. Zool., Vol. XLII, pp. 1-50. 

 The Mountains of Southernmost Africa, in Bull. Am. Geog. 



Soc., Vol. XXXVIII, pp. 593-623. 

 DUTTON : The Geology of the High Plateaus of Utah; U.S. Geog. 



and Geol. Surv., Rocky Mtn. Region. (Washington, 1880.) 

 GILBERT : Origin of the Physical Features of the United States, in 



Nat. Geog. Mag., Vol. IX, pp. 308-317. 

 JOHNSON : The High Plains and Their Utilization, in 21st Ann. 



Rept., U.S. Geol. Surv., Pt. IV, pp. 601-741. 

 LE CONTE : Theories of the Origin of Mountain Ranges, in Jour, of 



Geol., Vol. I, pp. 543-573. 

 POWELL : Types of Orographic Structure, in Am. Jour. Sci., 3d Series, 



Vol. XII, pp. 414-428. 



Physiographic Features, in Physiography of the United States, 

 pp. 33-64. (New York, 1895.) 



Physiographic Regions of the United States, Idem, pp. 65-100, 

 READE : The Origin of Mountain Ranges. (London, 1886.) 



