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Big Bend National Park, in the great southward loop of the Rio Grande on the Texas–Mexico border, packs half a billion years of geology into one park: the floor of a vanished ocean, the roots of two mountain-building episodes, a field of volcanoes, and canyons still being cut. It rises from under 1,800 feet on the river to nearly 8,000 feet in the Chisos Mountains.
| Where | the southern tip of the Trans-Pecos, Brewster County, southwestern Texas |
| Established | June 20, 1935 |
| Size | about 801,163 acres (324,219 hectares) |
| Elevation | under 1,800 ft (549 m) on the river to nearly 8,000 ft (2,438 m) in the Chisos |
| Also | a Biosphere Reserve since 1976 |
Canyons, desert, volcanic country, forested mountains and a river that never stays the same — few parks hold so many landscapes.
Four chapters
The rocks run from the early Paleozoic to the present, and include sedimentary rock, lava and ash, and 24 separate kinds of intrusive igneous rock — magma that cooled underground. Most of the jumbled landscape you see, though, is Cretaceous or younger.
| When | What happened |
|---|---|
| Paleozoic | An ocean covered the area for much of the era, then closed as two great landmasses collided and pushed up the Ouachita Mountains |
| Cretaceous | Shallow seas flooded the region, then drained away as a second round of mountain-building — the one that raised the Rocky Mountains — heaved up huge blocks of rock |
| From about 30 million years ago | The crust began to stretch and pull apart. Volcanoes erupted and the ground broke along vertical faults |
| Since then | Mostly erosion. The Rio Grande has carved deep, sheer-walled canyons through the folded layers and tilted fault blocks |
Big Bend belongs to the southern Basin and Range, the province of parallel ranges and basins made by that stretching of the crust, and shares its history with country far beyond the park.
Maps and reports
The Park Service's Geologic Resources Inventory, which maps the geology of more than 270 parks, has covered Big Bend: a scoping summary, digital geologic maps for GIS, a report on the park's geology and how to manage it, and a poster of the map. The park's soil survey is complete too. Everything is free on the NPS DataStore.
Sources
Written from "NPS Geodiversity Atlas — Big Bend National Park, Texas", National Park Service Geologic Resources Division, a work of the United States government in the public domain, which cites Maxwell and others (1967), Turner and others (2011) and Anderson (2017).
In these collectionsBig Bend National Park
Licence: CC0 1.0 (public domain) · Adapted from www.nps.gov
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