Wind ErosionWind ErosionExplain how wind causes deflation and abrasion. Distinguish how loess and dunes form.

Wind Erosion• Different types of erosion.

Wind Erosion• Question: How would wind and other

types of erosion be different?– Air usually cannot pick up heavy

sediments. – Wind carries sediments over large

areas.– Wind can place dust high into the

atmosphere and thousands of miles away.

Wind Erosion• Deflation erosion: Wind erodes loose

sediment, such as silt and sand.

Wind Erosion• Abrasion Erosion: When

windblown sediment strikes rock, the surface of the rock gets scraped and worn away.

Wind Erosion• Question: What process do we

use that is similar to wind abrasion?

• Sandblasting: Machines that use sand and water under high pressure to clean dirt from stone, concrete, or brick.

Sandblasting

Wind Erosion• Sand storms: Most sand storms occur

in deserts.

• Wind blown sand grains form a low cloud.

Reducing Wind Erosion• Question: What is the best way to

slow or stop wind erosion?

• Plant vegetation.

Reducing Wind Erosion• Reduce wind erosion by planting

wind breaks.

Reducing Wind Erosion• Windbreaks: As the wind hits the

trees, its energy of motion is reduced. It is no longer able to lift particles.

Reducing Wind Erosion• Roots: Especially along sea coast

and deserts. Plants with fibrous root systems help stop wind erosion.

Deposition by Wind

• Question: What happens to sediments that are blown away by wind?

• These sediments are eventually deposited.

Deposition by Wind

Deposition by Wind

• Loess: Fine-grained sediments deposited by wind.– Many farmlands in the midwest have

fertile soil that developed from loess.

Deposition by Wind

• Dune: A mound of sediment drifted by the wind.– Air drops sediment when its energy

decreases. Sediment starts to build up behind the object.

Deposition by Wind

• Moving dunes: A sand dune has two sides.– The side facing the wind has a gentler slope.

The side away from the wind is steeper.

Deposition by Wind

• Moving dunes: Unless dunes are planted with grasses, most dunes will move away from the direction of the wind.

• Some dunes are known as traveling dunes because they move rapidly across desert areas.