Sandstone Fins at Arches NP from the Air
This image shows the first step in the formation of sandstone arches. As the Colorado Plateau was compressed and uplifted, in places, layers of sandstone were turned 90 degrees. Relentless erosion then started separating layers. When wind and water encounter a weak area in the middle of a fin, a hole may form and eventually turn into an arch. These fins can reach several hundred feet high.