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,” �...