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