Between Terlingua and Lajitas, the road continues to cross various limestone units of Cretaceous age. After passing white, thick beds of steeply-dipping Cretaceous limestone of the Pen formation in roadcuts about four miles west of Terlingua, you will see the roadside topography open out into a broad valley where huge alluvial fans slope toward the river. Intrusive volcanic rocks are seen to the north as odd-shaped hills and mesas, whereas Mesa de Anguila and its battlement walls of solid Cretaceous limestone fortify the sky to the south. Imposing flatirons of tilted Cretaceous limestone are also seen along this stretch, where they border the south flank of a large fold called the Terlingua monocline.
Tilted sections of flaggy-bedded, yellow-tan Boquillas limestone still you around the town of Lajitas, located at the base of Lajitas Mesa, where Comanche Creek joins the Rio Grande.
Lajitas is developing as a small tourist resort, and the new museum and desert garden east of town is a pleasant stop. Across the Rio Grande at Lajitas notice how the large mesa surface curves downward toward the river giving the distinct impression that rocks can bend, fracture, and break, if pressure is applied slowly, rather than quickly, in the earth's crust.
Darwin Spearing, Roadside Geology of Texas