After Carlsbad we continued our trek westward across New Mexico stopping next in the Alamogordo area. Our primary objective was White Sands National Monument but we managed to sneak in Three Rivers Petroglyphs National Monument and Aguire Springs National Recreation Area just for grins. White Sands is a large dune field made completely out of gypsum sand, so it is brilliant white instead of the tan or black of most dunes. For geology buffs the process that forms the dunes goes something like this. Anyway, after the valley collapsed, the sides of the ridges along the fracture line now have layers of gypsum exposed to the elements.
Rain dissolves the gypsum, carrying it into the valley.
However, because the valley has no drainage outlets, the gypsum-laden water collects in a Lake XXX and during dry times is deposited on the valley floor as the lake dries up. Wind takes care of the rest, moving the sand into dunes which can sometimes move more than 30 feet per year. OK, enough geology. White Sands is worth a trip and I had a lot of fun jumping off the tops of dunes and generally looking silly. When I was a kid going to the Jersey shore walking on the dunes was strictly taboo, because the dunes protect the beaches.