In the stark, sun bleached deserts of the American Southwest and other arid regions, strange trails sometimes appear thin lines etched in the sand behind small, gravel sized gypsum crystals. The crystals have moved, often in large numbers, yet there are no footprints, no windblown debris, and no signs of animal activity. What’s causing these eerie, silent migrations?
The answer lies in a mix of geology, physics, and nature’s subtleties.
Mysterious Movements in Dry Landscapes
Gypsum, a soft mineral often found in desert playas and salt flats, can form small crystal pieces that rest loosely on the soil surface. Researchers observing locations like White Sands National Park have long been puzzled by the unexpected displacement of these crystals across seemingly stable, dry terrain.
Initially, scientists considered obvious culprits wind, animals, or seismic activity. But none fully explained the uniform trails or synchronized movement of dozens or hundreds of pieces at once.
The Role of Water, Ice, and Wind
Recent studies have revealed that a rare combination of conditions allows these gypsum crystals to move conditions involving thin layers of water and ice, sometimes aided by light wind.
Here’s how it works:
- After rare rain or dew, a shallow sheet of water forms on the flat desert surface.
- As temperatures drop at night, this water can freeze, forming thin, transparent ice sheets around or under the gypsum crystals.
- Morning sun weakens the ice, and gentle breezes nudge the floating ice sheets carrying the crystals with them.
- As the ice melts, the crystals are left in new locations, sometimes several feet from where they began, often in coordinated trails.
This mechanism is similar to the one behind the famous “sailing stones” of Death Valley, but with smaller objects and less dramatic motion.
Why Gypsum?
Gypsum is particularly sensitive to environmental changes because it’s:
- Lightweight enough to be carried by ice or water
- Soft and fragile, making it unlikely to move through strong impacts
- Common in evaporite environments where these rare movement conditions can occur
Its unique properties make it the perfect candidate for subtle, natural relocation across flat, wet, temporarily frozen surfaces.
A Delicate Dance of Nature
The movement of gravel-sized gypsum crystals is a striking reminder that even the harshest, driest environments have their quiet mysteries. These seemingly inanimate pieces of mineral are, in fact, part of a delicate, slow motion dance driven by physics and weather.
And while the desert may seem lifeless and still, science continues to reveal the invisible rhythms that shape its surface.
