After climbing the rugged path into Palm Canyon, I turned around to take in the scene. The space between the canyon’s walls opened a window onto the dry, hot desert several hundred feet below. The vista I photographed framed a picture reminiscent of early westerns; B-roll for a John Ford film, with brilliant light from the western plains bleeding into the far mountainous horizon that surrounds this sheltered enclave. It was a stage set, promising a drama ready to unfold, with the appearance of a solitary figure—the lawman or rustler—silhouetted in profile against the hazy desert heat.

These shaded walls of rhyolite, a volcanic rock that easily cracks and fractures into vertical ramparts framing the canyon’s entrance, separated the space I was in, from the flat, expansive La Posa Plain below. A faint track led up through a narrowing ravine briefly sunlit during midday. The slopes featured desert cacti such as saguaro, agave, and cholla, as well as palo verde trees and wildflowers along its streambed.

As an oasis, it protected plant life from the hot, dry Sonoran Desert. The canyon shelters not outlaws but, according to its name, the remnants of a relic species: a grove of rare native palm trees preserved within a cool, moist recess of this volcanic canyon. Descendants of palms that grew in this region during the last period of North American glaciation 10,000 years ago, botanists believe, gradually migrated into this canyon as the climate grew hotter and drier. The canyon serves as an ecological ‘island,’ and with its half-mile-high walls, limited sunlight, and available moisture, the palms depend on and thrive within its unique geography and microclimate.