Ernst Tinaja Trail

Ernst Tinaja Trail is a 1-mile out-and-back from a small Old Ore Road pullout to a natural limestone pool at the mouth of a canyon. Plan about one hour; the route rises roughly 20 feet. The nearly level path follows a high bank beside a tributary of Tornillo Creek, crossing deep sand and strips of bedrock. Near the pool it merges into the sandy creek bed; smooth, water-worn ledges make the final approach a short scramble.

The signed parking area is about five miles along Old Ore Road from its southern end. This is a primitive backcountry road, not a paved turnoff: when it is open, reaching the trailhead requires a high-clearance vehicle with true four-wheel drive. The parking area is small. Pets are prohibited on park trails. Old Ore Road was used in the early 1900s to carry ore from Mexican mines to the railroad in Marathon.

The destination is a 13-foot natural rock pool in the creekbed, with steep smooth sides and water year round. Look for orange swirling bands in the limestone and giant oyster fossils. In Spanish, tinaja means a large earthen jar; in Big Bend the word describes natural water holes shaped by erosion. The pothole sits in Buda Formation limestone, with marine fossils and iron-rich bands in the higher Boquillas beds.

The rock around the water has been smoothed by flowing creek water and can be slippery, especially where the short scramble reaches the pool. Keep sure footing near its steep edge. For a photo, frame the dark water together with the layered orange and pale limestone; that shows both the pool and the geology that makes this stop distinctive.