White Sands National Monument

I guess I'm now officially "old." :)

We drove out to White Sands National Monument and I bought an Interagency Senior Pass (this is the old "Golden Age Passport"). That, and the fact that I'll be receiving my first Social Security payment this month, puts me firmly in the "senior" category.

The sands of White Sands NM are white because they are composed of gypsum, not the usual gray-looking silica that most of us along the Pacific Coast are familiar with (sand in other areas of the world may be composed of other materials, such as volcanic rock in the Hawaiian Islands or limestone found in tropical and subtropical coastal areas).

White Sands NM is located in the Tularosa Basin which was covered by a shallow inland sea 250 million years ago. 70 million years ago, when the Rocky Mountains were being formed, the gypsum-bearing marine deposits from this inland sea were lifted up into a giant dome which began collapsing around 10 million years ago (the original sides of this dome now form the San Andres Mountains to the west and the Sacramento Mountains to the east).

Most of the time, gypsum eroded from mountains gets washed out to sea, but the Tularosa Basin has no outlet to the sea. Therefore, all the water flowing into the basin either sinks into the ground, or gathers in shallow seasonal lakes called Playas.

Some of the animals that live in the White Sands NM, like the pocket mouse, two different kinds of lizards, and several insects, have developed a white coloration to blend in with the sands.