Christopher, I have my own idea of the erosive mechanism in action here. Notice the lichen clusters on the outside of the formation are growing. To me this invalidates what is normally ascribed to wind-borne sand. If the outside of the formation is unscoured by that how could these intricate holes been created by wind erosion? Simply put, they couldn't. My humble theory (I'm not a Geologist and therefore not credible) is that it is all caused by slow water flow through the sandstone formations (more flow in the more porous areas, less in the harder areas) and the effects of expansion and contraction caused by heating and cooling. It is very hot at times in the summer and very cold at times in the winter. Observing the eroding surfaces it is occurring in plate-like fashion rather than a grain at a time. This also rules out wind abrasion and to me supports my hypothesis. The erosion pattern changes as erosion takes place and frees up the water flow in new more porous places. Jim