The Llano Estacado[Texas 207]


[Map]

The Llano Estacado is part of the High Plains, straddling the Texas - New Mexico border between Interstate 40 on the north and Interstate 20 on the south, or, roughly, between Amarillo and Midland-Odessa, Texas. It is bounded on the west by the Pecos valley, and on the east by the red Permian plains of Texas. Its extent is, therefore, about 250 mi. north to south, and 150 mi. east to west, an area of 37,500 sq. mi. The Llano is a very flat, semiarid plateau, ranging in elevation from 5000' on the northwest to less than 3000' on the southeast, sloping more or less uniformly to the east-southeast at a rate of at least 10' per mile. The slope is imperceptible to an observer on the plateau. The Llano is dry and treeless, the prevailing wind is from the southwest, and mirages are a frequent occurence under the hot sun.

The distinguishing characteristic of the Llano is the Caprock Escarpment, seen most prominently on the north and west sides, a precipitous cliff usually about 300' in height, seeming to be an almost impenetrable defense for the plain. The cliff on the north facing the Canadian river was seen by Francisco Vásquez de Coronado in 1541 on his way east from Cíbola, leading him to name the plateau the Llano Estacado, or Palisaded Plain. The name is usually mistranslated Staked Plain, and fanciful stories have been created to explain this title. The cliffs are easily seen to the south from Interstate 40 just east of Tucumcari. This is probably the best place to view the feature that gave the region its name. The photograph below shows the escarpment from a point on the plateau south of San Jon, looking northeast. Fragments of the caprock are seen in the foreground, and the escarpment on the other side of the Canadian River is seen in the distance. Further south, the Mescalero Ridge is a similar line of palisading cliffs, facing the Pecos valley.

There are several popular explanations of the name, all based on an incorrect translation of the word "estacado," which means "palisaded," not "staked." Some allude to yucca stems, others to actual stakes driven into the ground as landmarks, and still others to similar, even less plausible objects. None of these have ever been evident enough to be responsible for the name, especially not to Coronado riding along the Canadian.

[Scarp]

The Llano is, however, by no means uniformly surrounded by an escarpment. Highways and railways generally climb on to it in places where the fortifications have been breached and dissected by stream erosion. Interstate 40 ascends the plateau about 60 mi east of Tucumcari, at an angle to the escarpment facing the Canadian River. US 60-84 and the railway take advantage of Taiban Creek further south, where the escarpment is not so evident. US 70 and the railway use a much subdued slope west of Alida where, after climbing to over 4600', the way descends into the Pecos Valley at about 30' per mile. Mescalero Ridge begins just south of US 380. This prominent escarpment is crossed by US 82 towards its southern end, where it softens and is practically gone by the time it is crossed by US 180-62. Further south, the Llano becomes lost in the sands of West Texas.

On the eastern margin, the climb of US 285 and the railway between Memphis, Clarendon, and Claude is a typical approach. There is no evident escarpment, but the change in the scenery from the red hills to the sandy plain is striking as a long gangplank between two headwater streams of the Red River is ascended. Going south from Claude on Texas 207, the Caprock escarpment is spectacularly seen bordering Palo Duro Canyon, cut by the Prairie Dog Town Fork of the Red River. The upper part of the canyon is a state park in which the structure of the Llano is clearly observed. Further south on the same road, the escarpment is seen where Tule Creek has cut into the plateau. At Caprock Canyons State Park, just north of Quitaque, the escarpment can be seen to the west. The Brazos River makes a deep incursion into the plateau near Lubbock. The southwestern edge of this valley is used by US 84 and the railway to cross the escarpment between Slaton and Post. Further south, the escarpment becomes much less prominent near the Colorado River headwaters, and finally disappears beneath an ocean of sand blown in from the west. The photograph shows the edge of the Llano from the overlook at Palo Duro Canyon State Park.[Overlook]

The surface of the Llano is remarkably flat, reminding one of the sea, and it is conceivable that the curvature of the earth could be perceived as it is on the sea. The area around Levelland and Brownfield, Texas, would be a good place to look for grain elevators sinking beneath the horizon. However, the surface is not ideally flat, showing shallow draws, often without external drainage. Many temporary, and some permanent, lakes are found, often occupying 'blowout' basins in the loose, dusty surface. Most of this water is probably pumped. It should be noticed that, although the surface is very flat, it is not by any means level, since it dips uniformly to the ESE at 10' per mile or more, and what surface water there is tends to flow in this direction.

The 'bedrock' of the plain is the indurated top of the Ogallala Group, a hard caliche layer called the Caprock. This was formed when surface drying caused mineral-laden water to rise by capillary action to the surface. Evaporating, the minerals were left behind to cement the otherwise fairly loose sandy sediments of the Ogallala Group. The Caprock is generally covered by sands and soils. Where soils predominate, the land is fertile when irrigated, and is devoted to field crops, principally grain. Irrigation water is mined from the deeper parts of the Ogallala Group by electric pumps, since there is almost no usable surface water. The pumped water is used much more rapidly than it is replenished, so eventually the Llano will return to its natural state of sparse grassland, less its subterranean water, gas, and oil. The average rainfall is less than 20" per year, and the average July temperature above 85 F, so most of the precipitation is lost to evaporation, and cannot support dry-land farming.

The Ogallala Group is a late Tertiary (Pliocene) sheet of sediments spread over the area east of the Rocky Mountains from Wyoming to Texas, rather recently in a geological sense, when the Colorado Plateau and Rocky Mountain regions were elevated from near sea level to about their current elevations, and the eroded sediments (mainly earlier Tertiary rocks) spread over the low plains to the east. The Rocky Mountains had been formed much earlier, at the end of the Cretaceous and the beginning of the Tertiary eras, and had been worn down to near flatness before the late Tertiary uplift. In the northern areas, the Ogallala was spread over earlier Tertiary and Cretaceous rocks, but in the Llano Estacado area erosion had removed everything down to the Triassic, and even to the Permian redbeds. At the southern end, some Cretaceous limestone remained, however. The Ogallala was laid down over all of this by lazy, sandy streams near sea level, which produced the flatness of its surface. Subsequently, the uplift to the west progressed to the east, raising and tilting the Ogallala surface to its present position, and changing the environment from depositional to erosional. Some major rivers, such as the Pecos and Canadian, incised their courses deeply as the region was elevated, while others, such as the Red, Brazos, and Colorado, arose on the dip slope. The erosion of these rivers has now defined the area of the Llano Estacado, separating it from its Rocky Mountain sources and from other parts of the High Plains.

Other areas of the Ogallala surface, or High Plains, have the same history. In Wyoming, it is still in contact with the mountains west of Cheyenne (the 'Gangplank'), but elsewhere it is separated from the mountains by valleys of Cretaceous and earlier rocks due to active erosion at these higher levels. Rivers such as the Platte, Arkansas, and Cimarron have sliced it into segments. Only in the Llano Estacado area has the formation of the Caprock given rise to a prominent, distinctive, palisade-like escarpment, as well as to a remarkably flat surface. Another distinctive characteristic is that the surrounding rocks are often red, as in Palo Duro Canyon, making a striking contrast with the light-colored rocks of the plateau. In some other places, the erosional edge of the High Plains is marked by 'breaks' or other abrupt changes of scenery, as in eastern Wyoming and western Nebraska. In these areas, the High Plains are usually sandy, rolling plains with normal, branching drainage, not flat surfaces without continuous streams.

General Randolph Marcy described the Llano in 1872 as a "great North American desert" 400 miles from north to south, 250 miles from east to west, at 4000 ft elevation, with "not a tree, bush or water." If you wanted to travel over it, you had to bring water for yourself and your animals. The Llano was then a refuge for the bands of Kiowas and Comanches who did not wish to be cooped up in Oklahoma. One of the last battles was fought in bitter cold on 2 December 1874 in Palo Duro canyon. The waterless surface was very difficult for the U. S. Calvalry to cope with, and it was easy to disappear into the slight draws of its featureless expanse, or into the labyrinths of canyons like Palo Duro. All the water you see on the Llano today, which makes agriculture possible, is brought to the surface by electrical pumps. Before electricity, grazing was possible and large ranches existed. However, grazing soon destroyed the fragile grass. The scanty rainfall just evaporates or disappears into the porous soil, and cannot refill the perched aquifer at the rate it is being depleted. There are no nearby sources of abundant water, and the Pecos runs nearly dry from irrigation diversions. When the store of water is gone, there will be no more to support the large cities of Lubbock and Amarillo. There was a permanent oasis, Monument Spring, not far from Hobbs, that was one of the rare watering places. The "monument" was a pile of caliche raised by the Indians to guide people to the spot.

Turkey is a small town on the red plains just east of the escarpment, near Caprock Canyons State Park, where the scarp can be seen quite well, unusually for the eastern flank. The photograph shows the main street on a normal bustling day.

[Turkey]

References:

  1. W. A. Matthews III, The Geologic Story of Palo Duro Canyon (Guidebook 8, Bureau of Economic Geology, University of Texas at Austin, 1969)
  2. D. Spearing, Roadside Geology of Texas (Missoula, MT: Mountain Press Publishing Company, 1991) Chapter VII.
  3. V. H. Whitlock, Cowboy Life on the Llano Estacado
  4. (Norman, OK: Univ. of Oklahoma Press, 1970)


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Composed by J. B. Calvert
Created 22 August 1999
Last revised 22 May 2001