Eolian Processes and Landforms
Arid and semi-arid regions cover what percentage of the land surface on earth?
35%
Barchan Dune
A crescent-shaped heap of sand that moves across a flat, pebble-covered plain; points of the crescent are directed downwind
Playa
A dried lake bed that forms when runoff collects in closed topographic depressions in arid regions
Butte
A prominent, steep-sided hill or peak; an eroded mesa
Rain Shadow
A region having little rainfall because it is sheltered from prevailing rain-bearing winds by a range of hills
Blowout
A sandy depression in a sand dune ecosystem caused by the removal of sediments by wind
Saltation
A specific type of particle transported by fluids such as wind or water
Pinnacle
A steep-sided, narrow tower; an eroded butte
Plateau
A very broad, horizontal plain with a resistant caprock and steep cliff
Sand Dune
Any hill of loose sand shaped by the wind
The most common climate region on the earth?
Arid & semi-arid regions
In local areas of intense deflation, a depression may form called what?
Blowout
Parabolic Dune
Common dune type on semi-arid plains and coastal regions where vegetation is sparse & winds are strong & unidirectional; points are directed upwind
Eolian erosion takes place by what two factors?
Deflation & Abrasion
Over time only coarse fragments remain at the surface, forming what?
Desert Pavement
Transverse Dune
Formed when there is so much sand that it completely covers the solid ground
What are the four major deserts in North America?
Great Basin, Mojave, Sonoran, & Chihuahua
Coastal Foredune
Irregularly-shaped dunes found along the coastline; form above high tide
Caprock
Is a harder or more resistant rock type overlying a weaker or less resistant rock type
Coastal Blowout Dune
Is a type of parabolic dune; common on the east shore of Lake Michigan
Threshold Velocity
Is the minimum velocity required to transport a given particle size
What are examples of resistant caprock?
Limestone or Sandstone
Deflation
Occurs when wind blows loose, finer-grained particles away
Abrasion
Occurs when wind forces particles against the exposed rock surface, slowly wearing it down
The Dirty Thirties
Period of severe dust storms in the 1930s
Star Dune
Pyramid-shaped dunes with at least three faces and arms; formed in areas of multi-directional winds
Ventifact
Rock that has been abraded by wind-driven sand and/or ice
Sand grains typically bounce across the ground and typically only travel a few feet in the air at a time due too?
Saltation
What are the four primary factors that control the distribution of arid and semi-arid regions?
Semi-permanent high pressure systems between ~15-30 degrees latitude, Rain shadow effect downwind of mountain ranges, Distance from large bodies of water, & in cold regions, very low temperatures cannot hold significant moisture
What is an example of a non-resistant rock?
Shale
Loess
Silt-dominated sediment of eolian origin
Mesa
Similar to a plateau only smaller and completely surrounded by cliffs; an eroded plateau
Dust Storm
Strong, turbulent winds blowing over barren surfaces lift fine dust into the air, forming a dense, high cloud
Slip Face
The downwind/lee side of the dune, where the slope is steep
Crest
The highest point on the dune
Blackslope
The windward side of the dune, where the slope is gradual; zone of sediment transport
Desertification
Transforming a formerly vegetated landscape into one that is barren and highly susceptible to eolian erosion
Ecotone
Transition between the Sahara Desert to the north and tropical savanna to the south
Playa Functions
Water storage, groundwater recharge, improve water quality, and provide wildlife habitat
Large hill-shaped ventifacts are called what?
Yardangs
