Here's how it works:
1. Wind: The wind carries sand grains up the gentler windward slope of the dune.
2. Crest: As the sand grains reach the crest of the dune, they lose momentum and begin to fall down the leeward side.
3. Slipface: This downward movement of sand forms the slipface, which is typically at a steep angle (around 30-34 degrees).
4. Avalanching: As more sand accumulates on the slipface, it can become unstable and trigger avalanches, constantly reshaping the dune.
Key features of the slipface:
* Steep: The steepest slope on the dune.
* Leeward: Facing away from the prevailing wind.
* Active: The slipface is constantly changing due to sand movement and avalanches.
* Cross-bedding: The slipface often shows cross-bedding patterns, where layers of sand are tilted at different angles, indicating the direction of the wind.
The slipface plays a crucial role in dune formation and evolution, as it allows for the continuous movement and redistribution of sand.
