Creek water flows through the Navajo Sandstone above, leaving mineral deposits of various colors. Ýview The shapes of arches and overhangs are formed by the water flowing through the porous sandstone, then seeping out when it contacts the Kayenta formation aquitard. When the water meets the less permeable rock, it stops flowing down, and is forced to move horizontally between the two different rock types. This results in a weakening and eroding of the rock; the lack of support, plus gravity, makes portions of rock fall, usually in curved shapes, creating arches in the rock faces. Above the pools are Ponderosa Pines and Douglas-firs, trees not usually found at this low elevation, but thriving due to the shade and moisture available here.    -210 220 2 84