Wind stops blowing and sand falls
Explanation
Sand dunes are prominent depositional landforms created by aeolian (wind) processes, primarily observed in hot deserts and coastal regions.Mechanism of Formation:
- Wind acts as a geomorphic agent that erodes, transports, and deposits materials. It carries sand grains through suspension, saltation, and surface creep.
- Deposition is the primary process responsible for dune formation. This occurs when the wind loses the kinetic energy required to transport its sediment load.
- When the wind speed decreases or stops-often due to friction with the ground or encountering an obstacle such as a rock or bush-its carrying capacity drops. Consequently, the sand particles settle and accumulate.
- Over time, this accumulation grows into mounds or ridges known as sand dunes. Conversely, an increase in wind speed facilitates the lifting and transportation of sand (erosion), not its deposition.
Key Takeaway: Sand dunes form when wind velocity decreases or meets an obstruction, causing the transported sand to settle and accumulate due to reduced carrying capacity.