White Sands National Monument was formed when the Permian Sea retreated millions of years ago and left behind deep layers of gypsum. For thousands of years in shallow lakes, wind and sun have separated the water from the gypsum and formed selenite crystals. Wind and water break down the crystals making them smaller and smaller until they are sand. Steady, strong southwest sands keep gypsum sand moving, piling it up and pushing dunes into various shapes and sized.
The dunes were so large that at times it seemed we were at the beach. Luna had a blast, running through the sand. When we got back to the truck, she collapsed on the sand. Chacho tried to keep up with her at the beginning, but gave up halfway through and went back to a leisurely stroll. Sorry for all the pictures, but it's truly an oasis of basis among the desert plains.