The longest span at Arches is Landscape Arch, shown here. It stretches 291 feet across, just about the length of a football field. In 1973 Steve Tetreault and I managed to climb out onto it, finding it narrows to just 6 feet wide! Climbing on the arch is no longer permitted.
Paleoliquefaction features at Arches NP
One of the most unusual features I mapped at Arches Park were these enormous paleoliquefaction structures, which looked like gigantic sand boils, petrified in time. 20 years later Walter Alvarez at U.C. Berkeley explained these as the result of a nearby meteorite impact during the Jurassic Period. I mapped similar features in upper Lake Powell, though more subdued.