Desert landscapes are monotonous, relatively flat areas covered to various depths with sand.
Deserts and dry lands are concentrated in areas of ascending air masses and relatively low atmospheric pressures.
Despite infrequent rainfalls, erosional and depositional features of running water are important in desert landscapes.
Rainshadow deserts occur where air masses descend after first having risen to cross a mountain range.
40 and 50
20 and 30
5 and 10
0 and 5
Warm temperatures and high soil moisture contents accelerate chemical weathering.
Low temperatures and high soil moisture contents accelerate chemical weathering but inhibit mechanical weathering.
Warm temperatures and low soil moisture contents both promote rapid rates of mechanical weathering.
Temperature has no effect on rock weathering.
A hanging valley
The repose level
Alluvial fans typically rim desert valleys; playas form in the lowest, interior parts of the valleys.
Inselbergs are low, circular depressions on gently sloping pediments and bajadas.
Playas are typically covered with gravel-sized desert pavement and loess deposits.
Saline sediments and evaporites are common in inselbergs and pediments of desert landscapes.
A stream in a steep-sided, bedrock canyon in the mountains
Streams flowing in the numerous channels of an alluvial fan
A playa lake with a thick mud bottom
All of the above would promote infiltration.
Flat, upland surfaces, steep slopes and small alluvial fans
Extensive pediments and bajadas and small, deep playas
Inselbergs, extensive pediments and flat valley floors
Steep playas with extensive, bedrock alluvial fans and numerous sand dunes
Deflation removes the coarse fragments leaving behind a layer of loess.
Alluvial fans are eroded to form inselbergs with rocky surfaces.
Groundwater in an alluvial fan evaporates, leaving behind a surface layer of hard-baked mud.
Runoff and deflation carry off the silt and clay, leaving coarser particles behind.
Longitudinal dune gradient angle
Slope of an alluvial fan
A vertical cut bank in loess
Inclination angle of a dune slip face
A dune migrates in the direction of inclination of the slip face.
The more gently sloping surface is the leeward slope of the dune.
Sand is blown up the slip face and rolls down the more gently sloping flank of the dune.
In a sand dune, the more gently inclined strata lie parallel to the slip face.
Total annual precipitation
Mean annual temperature
Difference between annual precipitation and evaporation potential
Percentage of precipitation that falls during the summer months
Less than 30 percent is covered with dunes and drifting sand.
Wind erosion and deposition are important processes.
Running water has little effect on shaping the landscape.
Most desert areas are characterized by descending wind patterns.
The Empty Quarter of the Arabian Peninsula
The Sahel along the southern margin of the Sahara Desert
The Dust Bowl states of the Great Plains
The steppe lands of southern Russia, Ukraine, and Kazakhstan
Precipitation totals are low; dew points are lower in the summer than winter.
Evaporation potential exceeds actual precipitation.
Storms are infrequent and rainfall amounts are highly variable.
Wind is the dominant agent of erosion and sediment transport.
High in the moving air column as suspended load
By saltation in the first few meters above the land surface
By deflation of abraded desert pavement
By being picked up in swirling dust clouds and carried to distant blowouts
Cool, dry air aloft is descending; surface winds are blowing toward the equator.
Warm, humid air aloft is descending; surface winds blow away from the equator.
Warm, humid air is rising; surface winds are calm.
Cool, dry air at the surface is rising causing winds to blow away from the equator.
Deflation and sheet wash remove fine-sized materials leaving coarse, weathered, rock fragments concentrated at the surface.
Blowing wind removes fine-size soil particles; coarser particles abrades to sand size.
Running water deposits gravel and sand over the finer-sized soil particles.
Intense chemical weathering removes the sand- and silt-sized particles, leaving coarse rock debris covering the land surface.
Blew in from the dry areas in the Great Plains and southwestern desert areas
Originated as rock flour in Pleistocene glacial streams and rivers
Accumulated from flooding of the Mississippi River
Were originally deposited as barchanoid dunes and later redeposited by glaciers
East to west
North to south
South to north
West to east
Insulated icebergs floating in a hot spring
Blowouts cut from bedrock in mountainous areas
Lithified rock formed by cementation of wind-deposited, dune sands
Bedrock hills in a highly eroded desert landscape
A rise in sea level
The near surface water table
Type and density of vegetation
Areas of desert pavement
Vast, dry, steppe lands like the Great Plains
North central Africa
The dry valleys of eastern California and Nevada
Europe north of the Alps
Inselbergs and barcanoids
Pediments and playas
Bajadas and blowouts
Pediments and inselbergs
Sahara Desert; northern Africa
Atacama Desert in Chile, South America
Gobi Desert, China and Mongolia
Desert valleys of the Great Basin, U.S.