Gulf Coastal Plain

a lowland in the United States and Mexico that borders the Gulf of Mexico.

The Gulf Coastal Plain, which merges with the Atlantic Lowland in the northeast, has widths to 350 km. Composed of a layer of marine sedimentary rocks measuring up to 6,000–10,000 m thick, the plain contains large deposits of oil and fuel gas (seeGULF OF MEXICO OIL AND GAS BASIN). There are elevations to 150 m, with the surface rising gradually from south to north and forming several parallel cuestas. The Gulf Coastal Plain is intersected by the valleys of several large rivers, including the Mississippi, Alabama, Brazos, and Rio Grande (Río Bravo del Norte). The shore is dotted with lagoons and numerous estuaries. Except in the tropical southwest the climate is subtropical. The average January temperature is 4°–8°C in the north and as high as 12° C on the coast; the average July temperature is 26°–28°C. Annual precipitation reaches 600–800 mm in the west and 1,200–1,500 mm in the east.

Red soils and highly fertile soddy-calcareous (on limestones) and soddy-alluvial (in river floodlands) soils are prevalent. Marsh soils are also widespread. More than a third of the territory is wooded. There are pine woods with dwarf palmettos in the underbrush and mixed forests of pine with evergreen oaks, magnolias, and myrtles. Along the rivers there are water tupelo (Nyssa aquatica), bald cypress, and poplar forests, and in the west there is savanna. Most of the plain is planted with cotton, but along the coast there are tobacco, sugarcane, and rice plantings. Subtropical fruits are also grown. The large port cities are New Orleans, Houston, Corpus Christi, Tampico, and Veracruz.

G. M. IGNAT’EV