form where loose sediment accumulates. Requirements for
dune formation are:
- Loose sediment, usually sand-sized. Environments
with abundant loose sediment include beaches, river
bars, and deserts.
- Energy to move sediment, usually wind, but
dunes can form underwater in rivers.
- Some obstacle around which sand accumulates.
Areas with sparse vegetation commonly form dunes. Dunes
also form around rocks.
- A dry climate. Moisture causes sand grains to
stick together. Larger grains are more difficult to transport
by wind. Moisture also facilitates plant growth, which
stabilizes loose sediment and prevents it from moving.