Turkey Tales and Frog Fables: White Sands National Monument

Saturday, April 6 (Part III)

White Sands National Monument

We had started the day at Trinity Site near the north end of the White Sands Missile Range. Our next stop was in the southern portion of White Sands Missile Range, White Sands National Monument. It is the world's largest gypsum dune field, 275 square miles of white sand dunes, approximately 15 miles west of Alamogordo. All of the dune field is within the southern portion of White Sands Missile Range, although not all of the dune field is part of the National Monument.

Gypsum

Not only is the size of the dune field impressive, but the makeup of the sand is also noteworthy. Most sand is silica based. However, the sand here is gypsum (calcium sulfate dihydrate, CaSO₄·2H₂O). Gypsum, the same material used in making drywall or "gyp board", is quite soft and soluble in water! The gypsum was originally deposited in the mountains above this area. Snow and rainfall dissolved the gypsum and brought it into the valley, where it collected in Lake Lucerno. There is no outlet from this valley and it is very dry, so when the water in the lake evaporated it left behind crystalline gypsum, known as selenite, in the dry lake bed. The prevailing winds from the southwest broke up the crystals and blew them to the northeast, where they accumulated into the dunes. Most of this happened in prehistoric times, but it continues even today.

After a quick stop at the visitor center, we set off down the eight mile (16 mile round trip) dunes drive. We did not know what to expect, but quickly found this to be a remarkable place. At the edge of the dune field are parabolic dunes. Here plants anchor the constantly blowing (and hence constantly shifting) dunes such that the shape of the dunes become parabolic in shape.


Beginning of Big Dune Nature Trail, at the dunefield edge with parabolic dunes

We found the landscape and the few plants that have adapted to this harsh environment to be quite beautiful.

Frog with camera on the main dune road

The drifting sand means that the road needs to be continually plowed like snow. Even then, the sand was fairly deep in some places. We saw a car hopelessly stranded in deep sand in the parking lot of the Interdune Boardwalk.

Because of the moving dunes, all buildings within the dune field (e.g. restrooms and picnic shelters) are built on pallets so that they can be moved relatively easily, as needed. We never did find the Nature Center denoted on the map, but were told later it had been removed due to shifting dunes. In fact, the road is not paved beyond the Interdune Boardwalk because its location must be changed over time as the dunes shift.

Further into the dune field, the landscape changes as there is more sand and fewer plants.

That did not mean there were no people. The large dunes made for some interesting sledding.

We went on the "Sunset Stroll" with the ranger and found out much more about this interesting place. For example, there is water at rather shallow depths below the sand (at least between the dunes). One strategy adapted by the plants is to develop long stems that stick up through the dunes. These are then seen in their collapsed form after the dune moves forward as shown below. The sand is almost soft to the touch but, at least on the flat areas, was much firmer than expected. That is apparently due to the gypsum hardening when it becomes wet.

Although there was a pretty good crowd in the park on Saturday evening, we had the place nearly to ourselves when we returned the following morning. That gave us the opportunity to take some additional pictures.