An aerial photo of El Solitario, in Big Bend Ranch State Park, east of Presidio.
In the center of the Solitario, geologist Blaine Hall shows drawings of how the planet’s land masses fused to form the supercontinent of Pangaea, some 300 million years ago. Behind him are bands of rock that were thrust and folded into a horseshoe shape in that process – when North and South America collided.
Geology can seem abstract. Its scale and sweep are remote – how do we grasp the breadth of continents, the span of epochs and eons?
El Solitario, in Big Bend Ranch State Park, is a storied West Texas landscape. But armed with the perspective of geology, it’s also a revelation. Here, the Earth makes its ways comprehensible, transparent. Here, in the heart of the Texas Outback, impersonal processes become intimate and tactile.
The Solitario’s dimensions are most easily grasped from above. Ten miles in diameter, it could be mistaken for an impact crater. Aerial photos reveal a circular depression, surrounded by concentric rings of angled ridges, or flatirons.
“The lonely one,” “the hermit” – El Solitario is as withdrawn as a desert recluse. In Presidio County’s southeast corner, it’s part of Texas’ largest state park. Its geology, too, is singular.
Blaine Hall is a native West Texan whose geological career has taken him from ocean studies to the Sierra Madre and Patagonia. He’s worked at Big Bend Ranch. And he’s a great guide to the park’s geology.
“What’s so nice about this park is that you don’t have to pull out a book to look at this stuff,” Hall said. “You can see it, you can go up and touch it, you can stand on it and you can sit on it. I always tell people, just don’t spit on it.”
The Trans-Pecos once witnessed powerful volcanic activity. There was the massive eruption of the Chinati Volcano, the lava flows of the Davis Mountains. And 35 million years ago, magma began to swell beneath what’s now the Solitario.
The mushroom-shaped intrusion – a laccolith – pressed upwards on older rock, creating a high dome. Then the elements did their work. Water and weather hollowed the dome – revealing an epic West Texas story.
“So if you dome that up and erode it back, you get a window back into time,” Hall said. “That’s one of the things that’s so amazing about the Solitario, that you get this window back to where you can look at rocks that are half a billion years old.”
Driving east from the park’s Sauceda headquarters, the visitor crosses a vivid line. Red volcanic soil gives way to white rock. For many Texans, it’s a familiar hue. It’s Cretaceous limestone – laid down some 100 million years ago by an inland sea that covered much of Texas. Raised in the doming, it forms the Solitario’s outer boundary and flatirons.
Winding along the dirt road into the formation’s core, one travels back in time.
“See these blocks that have been pushed up here? That’s the Dagger Flat Sandstone,” Hall said. “That’s 520 million years old. So you have to get out and get down on your knees, and say hallelujah.”
The Solitario reveals distinct strata – blue-black Maravillas Chert, the glinting white of Caballos Novaculite. These rocks were formed in deep fathoms of a Paleozoic sea. Above, the shales and sandstones of the Tesnus Formation. They formed near land – because that sea was slowly closing up.
Three hundred million years ago, the planet’s land masses fused to form the supercontinent of Pangaea. As South and North America collided, these ocean rocks were caught in the middle – and thrust 60 miles inland.
In the great suturing of continents, mountains were raised. To the northeast, the Appalachians were produced, as were mountains in present-day Britain, Greenland and Norway.
In a cliff here, bands of Caballos Novaculite are folded into a giant horseshoe shape. A segment has been broken, driven over the fold. It’s evidence of the implacable force of the collision that formed this 5,000-mile-long mountain chain.
The mountains were high, but extended over a narrow band.
“This is just a small piece on the scale of a mountain chain, but what is so neat about the Solitario is that because of where it happened, where the Solitario developed, we happen to be able to see this,” Hall said. “If it had happened 10 miles to the east, or 10 miles to the west, we might not be able to see it.”
There’s more. Beneath the limestone is the Shutup Conglomerate. Containing chunks of chert and novaculite, it was formed as those ancient Texas Appalachians eroded away.
Big Bend Ranch State Park is one of Texas’ wildest places. Visitors come for backcountry adventure. But for the geologically curious, this land holds special wonders – here, on “the other side of nowhere.”
Nature Notes is underwritten by the Dixon Water Foundation and is produced by Marfa Public Radio in cooperation with the Sibley Nature Center in Midland, Texas. This episode was written by Andrew Stuart.