Aeolian landforms are features made by wind erosion, transport, and deposition, especially in dry regions with loose sediment and little vegetation. This cheat sheet helps students recognize how wind shapes deserts, coasts, and dry lake beds. It is useful for comparing dune types, identifying erosion features, and understanding why landforms change over time.
Key Facts
- Deflation is wind erosion that removes loose, fine sediment and can leave behind a stony desert pavement.
- Abrasion is the wearing away of rock surfaces when wind-blown sand strikes them like sandpaper.
- Saltation is the bouncing movement of sand grains along the ground and is the main way sand-sized particles move by wind.
- Suspension carries very fine dust and silt high in the air, sometimes for hundreds or thousands of kilometers.
- Dunes form where wind slows down, drops sediment, and builds a mound with a gentle windward slope and a steeper slip face.
- The angle of repose for dry sand is usually about 30 to 34 degrees, which controls the maximum steepness of a dune slip face.
- Barchan dunes are crescent-shaped dunes that form where sand supply is limited and wind usually blows from one main direction.
- A dune migrates when sand moves up the windward side by saltation and then avalanches down the slip face on the leeward side.
Vocabulary
- Aeolian
- Aeolian means caused, shaped, or transported by the wind.
- Deflation
- Deflation is the removal of loose surface particles by wind, often lowering the land surface.
- Saltation
- Saltation is the hopping or bouncing movement of sand grains pushed by wind near the ground.
- Slip face
- A slip face is the steep leeward side of a dune where sand avalanches downward.
- Barchan dune
- A barchan dune is a crescent-shaped dune with horns pointing downwind, formed under one main wind direction and limited sand supply.
- Loess
- Loess is a thick deposit of wind-blown silt that can form fertile soils far from its source.
Common Mistakes to Avoid
- Confusing the windward and leeward sides of a dune is wrong because the windward side faces the wind and is gentler, while the leeward side has the steep slip face.
- Saying wind can easily carry large gravel is wrong because wind mainly transports dust, silt, and sand, while larger particles usually remain as lag deposits.
- Assuming all dunes have the same shape is wrong because dune type depends on wind direction, sand supply, vegetation, and surface conditions.
- Mixing up deflation and abrasion is wrong because deflation removes loose particles, while abrasion wears down rock surfaces by impact from wind-blown sand.
- Thinking dunes stay fixed in place is wrong because many dunes migrate as sand moves up the windward slope and slides down the slip face.
Practice Questions
- 1 A dune has a slip face that points southeast. What direction is the wind most likely blowing toward?
- 2 If dry sand has an angle of repose of about 32 degrees, what is likely to happen if a dune slip face steepens to 38 degrees?
- 3 A sand dune migrates 6 meters in 3 years. What is its average migration rate in meters per year?
- 4 Explain why barchan dunes are more likely to form in an area with limited sand supply, while transverse dunes form where sand supply is abundant.