The plateau itself sits at elevations ranging from approximately 4,000 to 8,000 feet above sea level. The Colorado River and its tributaries have carved through it to create some of the most dramatic topography in North America — the Grand Canyon is the most famous result, but the canyon country of southeastern Utah and the adjacent corners of Colorado, Arizona, and New Mexico contains hundreds of miles of comparable formation. Blue John Canyon is one small thread in that system: an eleven-mile slot running north-northeast through Wayne County, Utah, carved by water action through Navajo sandstone, the deep red and orange stone that defines the visual character of canyon country.
The slot canyon sections of Blue John represent the geological extreme of this kind of formation. Where the canyon narrows to three feet between walls that rise fifty or a hundred feet or more, the proportional relationship between width and depth becomes almost disorienting. The sky visible from the slot floor is a thin strip of light far above. Sound behaves differently in these constricted spaces — voices carry strangely, echoes return quickly and distorted, the exterior world feels very far away. The canyon’s interior is cool relative to the desert above even in April, when temperatures on the surrounding plateau can reach the nineties by midday.
The chockstone that trapped Ralston was a function of this geology. Over geological time, boulders of various sizes have fallen into the canyon from above and become wedged at points where the walls narrow. These chockstones are a permanent feature of the slot canyon landscape — they are not unusual, not rare, not a freak occurrence. Canyoneers who traverse Blue John regularly encounter chockstones and have developed standard techniques for navigating them: chimneying (bracing hands and feet against opposite walls), downclimbing around them, rigging a rappel below them if the drop is significant. What Ralston encountered was not, on its face, an unusual obstacle. The problem was the specific combination of the boulder’s weight, its position in the narrowing, and the direction of his descent that turned a routine canyoneering obstacle into a trap.