An Amazing Boxworks (Tafoni, Gnammas) in the South fork of Mineral Canyon

This is an erosional feature sometimes called a boxworks. This was the most intricate one I had ever seen (south fork of Mineral Canyon, near Moab). Some web research shows that this is also called: honeycomb erosion, alveolar weathering, tafoni, or gnammas. Some interesting info is at http://www.tec.army.mil/research/products/desert_guide/lsmsheet/lstafon.htm; it is apparently not entirely understood how these form. A web search on "tafoni" will yield lots of examples of this sort of structure around the world.