Edwards Plateau
Geographers usually consider that the Great Plains at the foot of the Rocky Mountains actually continue southward from the High Plains of Texas to the Rio Grande and the Balcones Escarpment. This southern and lower extension of the Great Plains in Texas is known as the Edwards Plateau.
It lies between the Rio Grande and the Colorado River. Its southeastern border is the Balcones Escarpment from the Rio Grande at Del Rio eastward to San Antonio and thence to Austin on the Colorado River. Its upper boundary is the Pecos River, though the Stockton Plateau is geologically and topographically classed with the Edwards Plateau.
The Edwards Plateau varies from about 750 feet high at its southern and eastern borders to about 2,700 feet in places. Almost the entire surface is a thin, limestone-based soil covered with a medium to thick growth of cedar, small oak, and mesquite and a varying growth of prickly pear. Grass for cattle, weeds for sheep, and tree foliage for the browsing goats support three industries — cattle, goat, and sheep raising — upon which the area’s economy depends. It is the nation’s leading Angora goat and mohair producing region and one of the nation’s leading sheep and wool areas. A few crops are grown.
Llano Basin
The Llano Basin lies at the junction of the Colorado and Llano rivers in Burnet and Llano counties. Earlier, this was known as the “Central Mineral Region” because of evidence there of a large number of minerals.
On the Colorado River in this area, a succession of dams impounds two large and five small reservoirs. Uppermost is Lake Buchanan, one of the large reservoirs, between Burnet and Llano counties. Below it in the western part of Travis County is Lake Travis.
Between these two large reservoirs are three smaller ones, Inks, L.B. Johnson (formerly Granite Shoals), and Marble Falls reservoirs, used primarily to produce electric power from the overflow from Lake Buchanan. Lake Austin is along the western part of the city of Austin. Still another small lake, Lady Bird Lake (formerly Town Lake), is formed by a low-water dam in Austin.
The recreational area around these lakes has been called the Highland Lakes Country. This is an interesting area with Precambrian and Paleozoic rocks found on the surface. Granitic domes, exemplified by Enchanted Rock north of Fredericksburg, form the core of this area of ancient rocks.
High Plains
The Great Plains, which lie to the east of the base of the Rocky Mountains, extend into northwestern Texas. This area, commonly known as the High Plains, is a vast, flat, high plain covered with thick layers of alluvial material.
The Caprock Escarpment is the dividing line between the High Plains and the lower West Texas Rolling Plains. Like the Balcones Escarpment, the Caprock Escarpment is a striking physical feature, rising abruptly 200, 500, and in some places almost 1,000 feet above the plains. Unlike the Balcones Escarpment, the Caprock was caused by surface erosion.
Where rivers issue from the eastern face of the Caprock, there frequently are notable canyons, such as Palo Duro Canyon on the Prairie Dog Town Fork of the Red River, Blanco Canyon on the White River, as well as the breaks along the Canadian River as it crosses the Panhandle north of Amarillo.
The South Plains, also a leading grain sorghum region, leads Texas in cotton production. Lubbock is the principal city, and Lubbock County is one of the state’s largest cotton producers. Irrigation from underground reservoirs, centered around Lubbock and Plainview, waters much of the crop acreage.
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