Wind

Wind is different than water when it comes to erosion.

Why?

Wind can carry small materials uphill/upslope

Extreme winds can carry particles that are large!

Tornados Hurricanes

Wind movements happens two ways:

Airborne

Rolling action

Suspension is the term associated with airborne movement

Saltation is the term that describes the rolling action of larger particles

 

Generally, most of the movement of materials by wind occurs in areas of low precipitation, and minimal plant growth

Rule of Thumb

Deflation is the lowering of the land by removal of particles by the wind

Previous ground level

Desert pavement is what is left when steady winds have removed small particles and leave

larger particles

Abrasion is the process of wind blown particles wearing away at surfaces of rocks and other

features

Flute-like textures on the rock, possibly caused by wind abrasion, are clearly visible.

This process works because most of the sand particles are made of quartz that is

quite hard

Polishing of rocks can take place because of this process

Sandblasting and Abrasion• Wind can only lift sand to about 1 meter

high - results in “Mushroom Rock”• Frosted or Pitted sediments – rocks with flat

sides

Ventifacts are rocks that have been shaped by wind blown sediments

Wind Deposition 

Sand and sediments accumulate around objects that break the flow of wind

Vegetation helps do this!

Dunes are the results of these deposits

SAND DUNESare ridges of wind deposited sand

- Usually 3 to 15 metres high, but can reach 180 metres

- A continuously changing dune is ACTIVE Corbis Digital Stock

Dune conditions are dependent on the following

Availability of sandWind velocityWind direction

Vegetation present

Structure of a Sand Dune Windward side Leeward side

Wind direction

TYPES OF SAND DUNE1.) BARCHAN- most common type- crescent-shaped

Wind direction

backslope

slip face

2.) PARABOLIC DUNES- crescent-shaped but with the concave side on the windward side- usually elongated- may develop in associated with deflation hollows

Wind direction

3.) TRANSVERSE DUNES• low sand ridge at right angles to the wind direction• may form because of large amounts of sand

wind

4.) LONGITUDINAL DUNES• low sand ridges parallel to the wind direction• may form because of a limited amount of sand• also known as seif dunes

wind

Loess

Silt and clay particles that are deposited by the wind

Wisconsin is a state that has large buildups of loess

Loess, as seen in a soil horizon

LOESS• Finely textured sediment wind-blown long distances

• Wind-blown glacial debris formed large deposits