File:Annual report of the United States Geological Survey to the Secretary of the Interior (1899) (14763066102).jpg

Identifier: annualreportofun2171geol (find matches)
Title: Annual report of the United States Geological Survey to the Secretary of the Interior
Year: 1880 (1880s)
Authors: Geological Survey (U.S.)
Subjects: Geological Survey (U.S.) Geology Water-supply Forest reserves Mines and mineral resources
Publisher: Washington : G.P.O.
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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sloping plain,extending from a mountainous background (the Ouachita Mountains)to the Gulf, its eastern border attaining an elevation of about 500 feetin southern Arkansas. As it bends to the southwest its featuresbecome gradually modified until they present several notable variationsfrom the Coastal Plain to the east. The most notable differences arethe absence of a well-defined interior border between the OuachitaMountains and the Colorado River, the increasing proportion ofprairie, the different adjustment of the fall line of the rivers, and agreat embayment which the plain makes up the valley of the RioGrande, somewhat analogous to that of the Mississippi. Between the Ouachita Mountains and the Colorado River the CoastalPlain is so continuous with the Regional Coastward Slope, whichextends westward to the Rocky Mountains, that its border in thisregion must be an arbitrarily assumed line practically coinciding withthe coastward border of the Black Prairie as far south as the Brazos.
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HILL.J THE COASTAL PLAIN. 49 South of the Brazos the Balcones scarp gradually develops and makesa well-defined interior limitation of the Coastal Plain toward the RioGrande. The Coast Prairie—The Coast Prairie is a belt of prairie land notover 100 miles wide which borders the Gulf of Mexico in Louisi-ana and Texas. This is a grass-covered constructional plain, newlyreclaimed from the Gulf of Mexico, whose interior margin risesscarcely 100 feet above the sea. It is marked by an exceedingly levelsurface, hardly broken except by a few low-drainage grooves, whichbecome fewer and more faintly developed toward the Rio Grande.Upon it a youthful drainage system is being established, while theseaward extensions of the through-flowing streams cross it. Theserivers have wide and deeply indented thalwegs, with gentle, terracedslopes filled with old alluvium. The floor of the sea border of Texas is a submerged, gently sloping,sandy plain or shelf extending 50 miles seaward. By action of tide,wav

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