Geology
Arches
8 destinations along 7 roads
An arch is a slow accident. Water and ice pry into the parallel cracks of a sandstone slab, widen them into freestanding walls called fins, then hollow the weakest fins from within until only a ribbon of rock still spans the gap. Arches National Park holds more than two thousand of them, the densest gathering on earth — but the process runs anywhere the sandstone is right. And what is forming is also always falling: every arch is on its way down.