Potholes depressions eroded in sandstone on the sandstone is a result of geomicrobiologic process. Bacteria consume the siliceous minerals and diatoms sequester the silicon in solution. Wind then carries away the diatoms when the potholes dry up. The basins are also sealed by mats of cyanobacteria, fungi and fine settlement that creates a biofilm on the surface that prevents water from soaking through the porous sandstone. Toroweap/Tuweep is on the north rim of the Grand Canyon National Park on what is called the Arizona Strip. It is remote and uncrowded area with difficult roadways presenting challenges to even four wheel drive vehicles. Summers are hot and winters are cold, there is no water, gas, food, lodging, or phone service. Camping with an advance permit only.