Nature

Llano Uplift: A Geological Wonder in the Texas Hill Country

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A hallmark of the Texas Hill Country’s geology is the Llano Uplift. This feature literally stands out from the surrounding area as its granite rises higher than other parts of the Hill Country. How old is it? And how did it come to be a mountainous region in the middle of the Hill Country? The answers to these and other questions will help you to learn more about the geology of the Texas Hill Country and better appreciate the uniqueness of the region.

Age of the Llano Uplift

Llano Uplift Map

Photo: Wikimedia Commons

The rocks of the Llano Uplift come from the Precambrian era, which predates even the oldest dinosaurs. Most geologic time fits into the extended Precambrian, which lasted from 4.6 billion years ago to 541 million years ago. But the Llano Uplift does not extend throughout this time. The oldest parts of the area only date to 1.5 billion years ago. And this corresponds to a time when multicellular life reigned in the seas but land animals did not yet exist.

Creation of the Area

Enchanted Rock in the Llano Uplift is a large granite dome

Photo: Flickr/Lori Branham

Though its name suggests the land pushed upward, the exact opposite happened to expose the Llano Uplift. When the surrounding area of younger sedimentary rocks eroded away, it left behind granite at the heart of the uplift. Along with the rest of the Texas Hill Country, the Llano Uplift also rose in elevation during the Cenozoic when the Balcones Fault shifted, lifting the area to the west.

Composition of the Uplift

Llanite is found in the Llano Uplift

Photo: Flickr/James St. John

Many minerals abound under the surface of this area. These unusual rocks found in this region come from the older rocks exposed at the surface. For instance, rock hounds have found amethyst, quartz, galena, garnet, and even bits of gold. Some purport that llanite can only be found in the Uplift area, though geologists argue they’ve discovered it elsewhere, too. If you ever visit the Llano area, which includes Enchanted Rock State Natural Area, be sure to look down at the ground to possibly glimpse rocks that are millions of years old.

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