Deserts sometimes hold surprising mysteries. One of them: gravel-size gypsum crystals—large shards of gypsum—that seem to move across barren surfaces. How do these heavy crystals go from place to place when there’s barely any water and plants to help? Scientists have been studying this odd phenomenon, especially in arid places like northern Chile. Here’s what we know so far.
Main Mechanisms Behind the Movement
1. Gravel Devils (Small Intense Whirlwinds)
These are dry, convective, helical vortices—basically little whirlwinds powerful enough to pick up and transport large gypsum crystals. In the Andes of northern Chile, researchers observed “gravel devils” lifting crystals from a saline pan surface and dropping them several kilometers away, forming deposits or dune-like mounds. Geoscience World
To move stones this size, wind speeds must be surprisingly high—comparable to those in weak tornadoes or strong dust devils. These events are rare but strong enough to lift objects that normal winds cannot. Geoscience World+1
2. Saltation, Surface Creep, and Air Suspension (Aeolian Processes)
- Saltation: Particles bounce along the surface, knocking into others and gradually moving them.
- Surface Creep (Traction): Larger crystals roll or slide along the ground because wind pushes repeatedly on them—even if they don’t get fully airborne.
- Suspension: Rare for very large crystals, but sometimes they are lifted briefly and transported in the air. Wikipedia+1
These aeolian processes contribute especially when the crystals are broken into smaller pieces, or when surface conditions reduce resistance (dry, loose surfaces, little vegetation).
3. Breakage & Weathering
The gypsum crystals don’t always move intact. Over time:
- Temperature changes, freezing/thawing, or wet-and-dry cycles cause parts of huge gypsum crystals to crack, break and fragment.
- Once broken, smaller pieces are easier to move by wind or other mechanisms.
At places like White Sands, New Mexico, large gypsum crystals (selenite) form, then eventually break down into sand-size grains that then move with prevailing winds to form dunes. National Park Service
Why This Matters
- Geological Clues: Understanding these mechanisms helps scientists interpret ancient gypsum deposits and desert landscapes. Some landforms we see today may have been shaped by similar movements in the distant past. Geoscience World
- Desert Ecology & Preservation: Knowing how these crystals move can help in preserving unusual geological phenomena and understanding erosion processes in arid regions.
- Comparative Planetology: These kinds of gravel devils and gypsum movement are being studied as analogues for features on Mars—since Mars has gypsum and desert-like conditions. Forums+1
Conclusion
The movement of gravel-size gypsum crystals in deserts is explained by a combination of powerful, localized wind events (gravel devils), everyday aeolian (wind) processes, and gradual weathering that reduces size so transport becomes possible. These forces, though infrequent or slow, demonstrate how even seemingly immovable objects are gradually shifted over time in the desert’s harsh environment.