Los Caballos

Highly deformed rocks in the Ouachita Fold Belt, a northeasterly trending range, were uplifted about 275 to 290 million years ago. Intricate folding appears in whitish rock bands called caballos, the Spanish word for horses, exposed on both sides of the highway. The Ouachita Fold is comparable in age to the uplift that formed the Appalachians in the eastern part of the United States. The northwesterly trending Del Norte-Santiago range, the southmost extension of the Rocky Mountains, forms the southwestern skyline. Its rocks were deposited in a sea that covered the Ouachita Fold Belt after erosion had reduced the highlands and a later submergence lowered the area. Santiago Peak, named for a local man who was killed by Indians and buried beneath the peak, is the high, flat-topped mountain to the southwest. It was once a mass of molten magma that cooled and hardened underneath the earth's surface and was uncovered by later erosion. The Del Norte-Santiago range, uplifted and folded 40 to 60 million years ago, is not half the age of the Ouachita Fold. Together they form a remarkable fusion of old and young mountains unmatched at any other site in North America.

Texas · United States