Cutch and Kathiawar they are underlaid by Jurassic and Neocomian beds.
The tundra is a coastal plain, swampy and covered with undergrowth and underlaid by gravel.
These prairies are traversed by ridges, which facilitate irrigation, and are underlaid by an impervious subsoil, which facilitates both effective storage and drainage.
The plains, except in the south-east corner, are underlaid by sheets of water-bearing sandstone, which carry a volume of water under such pressure that in the valleys of the James river and the Missouri river and its western tributaries a strong surface flow may be obtained from artesian wells.
The Great Plains.A broad stretch of country underlaid by nearly horizontal strata extends westward from the 97th meridian to the base of the Rocky Mountains, a distance of from 300 to 500 in., and northward from the Mexican, boundary far into Canada.