Big Bend National Park Geologic History

Big Bend National Park Geologic History
Big Bend National Park in southwest Texas has a geologic history that goes back some 500 million years. During that time, the area has included vast oceans, volcanic eruptions and cataclysmic collisions, all of which helped to shape the region.

Paleozoic Era

During the Paleozoic Era, between 570 and 245 million years ago, the Big Bend area was covered by ocean, which has left layers of gravel, sand and clay. It wasn't until the end of this period, around 300 million years ago, that a collision between the continents of North America, South America and Africa caused the area of Big Bend to rise above sea level.

Early Cretaceous Period

During the early Cretaceous period, around 135 million years ago, the area was still covered by ocean and was home to tiny organisms like mollusks and ammonites. The remains of these organisms can be found among the sandstone and limestone deposits.

Late Cretaceous Period

The ocean levels receded throughout the Cretaceous period so that by the late Cretaceous period the area was a swampland with vegetation, clay and also dinosaur fossils such as the Texas Pterosaur.

Cenozoic Era

During the Cenozoic period, the oceans receded to where they are now and mammals began to appear. Around 35 million years ago, several large volcanic eruptions left the Big Bend region with volcanic ash and other debris that can be seen in-between layers of sediment, around the Chisos Mountains


The landscape around Big Bend continues to be shaped today through rainfall, which sweeps sand and silt away to lower elevations and the impressive Rio Grande River, which continues to carve through the canyons around Big Bend.

Article Written By Shiromi Nassreen

Shiromi Nassreen has been writing professionally since 2005. She specializes in travel and outdoor topics, and her articles have appeared in various print and online publications, including "DISfunkshion Magazine" and Matador Travel. Nassreen holds a Bachelor of Arts in theatre studies from Rose Bruford College of Speech & Drama.

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