How does this melted-wax erosion pattern form in sandstone?
Differential erosion, the "wax-drips" have been hardened by chemical deposition, usually by calcium salts, washed down from the soil at the top of the cliff. There are different mineral deposits that can cause this effect including but not limited to calcite, silica, iron, manganese, fine organic matter, alumina, and fine clay, to name a few, anything that can be deposited between the grains of the sand stone will do really. These minerals flow into the sandstone when wet and as the surface dries they act as a cement increasing the durability of the sandstone in the areas that have been wetted by the mineral rich water. The wind then erodes the surface of the rock and because the cemented material is harder it cuts more deeply into the rock between the water pathways.