Physical Geography 102
Desert Landforms I

Desert Landforms

Air Flow - air is a fluid
Behaves similar to flowing water

Physical Parameters

Wind Speed - rate of air flow measured in kph, mph, knots
Anemometer - device use to measure wind speed
Wind Direction - measured in the direction from which the wind is coming

Wind Erosion


Removal of loose sediment by the wind
Sediment must be dry
Sand and silt sized material will be moved
Larger material is generally left behind

Deflation Landforms

- Shallow depressions formed by removal of sediment
- Diameters range from a few meters to 1000 meters
Desert Pavement
- Fine material is removed from the surface leaving a cover of pebbles, cobbles and boulders
- Coarser material protect the fine material beneath the surface from further erosion

Abrasion - "sand blasting"

Impact of windblown particles on exposed surfaces will remove material from that surface
Abrasion will also reduce the size of the particles that are being moved

Generally limited to heights of 1 meter (2 meters max.)

Abrasion Landforms

Ventifacts - pebbles, cobbles or boulders that have been eroded on one or more sides by wind abrasion
Yardangs- ridges which run parallel to dominant wind direction, believed to be formed by abrasion
- pillars which are undercut by abrasion

Dust Storms

Heavy concentration of dust (silt-sized particles) in a turbulent air mass
Dust can be carried hundreds or thousands of meters into the air
Large dust storms can carry as much as 100 million metric tons of material

Dust Bowl of the 1930's
Dust Devils

Sand Storms

Low moving blankets of wind-driven sand
Sand reaches heights of 1-2 meters above surface
Often contain dust and sand

Desert Regions

A region with a mean annual precipitation of 10 inches or less, and relatively devoid of vegetation
Five types of deserts
- Subtropical Deserts
- Rainshadow Deserts
- Continental Deserts
- Coastal Deserts
- Polar Deserts

Regions Subtropical Deserts

25°-30° Latitude
Form in response to dry descending air mass in Hadley Cell circulation

Rainshadow Deserts

Mountain ranges block the passage of moist air
Leeward side of range will be arid

Continental Deserts

Centralized location in continental interiors
No nearby, large sources of water

Coastal Deserts

Form where there is a cold ocean current offshore.
Coastal fogs are common in these areas.

Polar Deserts

Cold air is unable to hold much moisture
Polar areas are arid - very little precipitation
Deserts are not defined by temperature