Eolian Systems
What is deflation?
Deflation is loose sediment (sand and dust) that is blown away from the surface.
What is desertification?
Desertification is the loss of farmable land on the margins of deserts, can be caused by humans and/or climate changes.
What are deflation basins?
Dips in the surface caused by deflation.
What are Ergs?
Ergs are sand seas.
What are the parts of a sand dune?
Interdune-area before the sand dune starts an upward slope. Stoss Slope-the upward sloped part of the dune. Crest-top of the dune Brink-point at which the sand dune begins a downward slope Slipface-the downward sloped far side of the dune, and the wind shadow part of the dune.
What are lag deposits or desert pavements?
Lag deposits or desert pavements are made up of the coarser heavier material that is not carried away by deflation. (Arizona)
What are Star Dunes?
Star dunes are shaped like a starfish. Star dunes are made up of mounds of sand having a high central point with 3 or 4 arms or ridges radiating out (typical of N. Africa and Saudi Arabia) formed from winds blowing in 3 or more directions.
What are Ventifacts?
Ventifacts are any bedrock surface or stone that has been abraded or shaped by wind-blown sediment in a process similar to sand blasting. The sides of the rock becomes flat on the side that the wind is blowing.
Eolian Systems
Wind Systems
What is responsible for the specific formation of the different types of sand dunes?
Wind Velocity, sand supply, and constancy of wind direction are responsible for the formation of different types of sand dunes.
Wind Patterns are determined by?
Wind patterns are determined by: a. Variations of solar radiation with latitude b. The Coriolis effect c. Configuration of the continents and oceans d. Location of mountain ranges
What are Yardangs?
Yardangs are distinctive linear ridges (not as common as ventifacts) restricted to the most arid parts of desers which are relatively sand-poor and where vegetation and siol are minimal. Some evidence that the Sphinx of Egypt was made out of a yardang.
Deposits of wind-blown sand are?
Deposits made by wind-blown sand are either: a. sand sheets-deposits that are wind-blown sand that is nearly flat and made of grains that are too large to move by saltation. b. sand dunes
What is Loess?
Wind-blown dust
What are Barchan Dunes?
Barchan dunes are cresent shaped dunes that require a limited supply of sand and moderate winds. The way that the horns of the Barchan are pointing indicates the direction of the wind.
What does Loess do to the landscape?
Loess forms blanket deposits which can mask the older landscape beneath them.
Most large deserts are found at what altitude?
Most large deserts are in the low latitudes near 30 and 35 degrees. (Sahara and deserts of Asia) Most other deserts are found in rain shadows.
Is wind an efctive agent in eroding the landscape?
No, wind is not an effective agent in eroding the landscape, but it can produce small features.
What are Paleosols?
Paleosols are ancient soils.
What are Parabolic Dunes or blowouts ?
Parabolic Dunes or blowouts are cresent shaped like a Barchan Dune but Parabolic develop along cosatlines where vegetation partly covers a ridge of wind-blown sand
What are rain shadows?
Rain shadows are areas behind mountain ranges that intercept moisture laden air currents. Ex. Moisture rich clouds come off the Pacific air currents push those clouds towards the mountain ranges of Nevada and Utah. As the wind pushes the clouds up the mountains the clouds drop their moisture in the form of rain. When the cloud passes over the top of the mountain it has very little rain to drop on that side of the mountain causing a rain shadow.
What are sand dunes?
Sand dunes are deposits of wind-blown sand that often originate where there is an obstacle such as large rock, clump of vegetation, or fence post. These create "quiet" air behind them.
How do sand dunes form?
Sand dunes are formed when sand is blown up (Stoss Slope) or around the obstruction and into the protected area called the slip face (wind shadow), its velocity is reduced and deposition occurs. Once a small dune forms it acts as a barrier itself.
How do sand dunes migrate?
Sand dunes migrate as sand grains are blown up and over the windward side of the dune and accumulate on the lee side.
What are sand sheets?
Sand sheets deposits that are wind-blown sand that is nearly flat and made of grains that are too large to move by saltation.
What are the effects of wind erosion - abrasion?
The effects of wind erosion-abrasion: a. artificial sand blasting b. Ventifacts-any bedrock surface or stone that has been abraded or shaped by wind-blown sediment in a process similar to sand blasting. c. Yardangs-distinctive linear ridges (not as common as ventifacts) restricted to the most arid parts of desers which are relatively sand-poor and where vegetation and siol are minimal.
What is the main result of wind activity?
The main result of wind activity is the transportation of loose, unconsolidated detritus.
How are larger particles moved by the wind?
The wind moves larger particles by saltation. (the particles is more rolled across the ground than carried through the air.)
How are smaller particles moved by wind?
The wind moves smaller particles by suspension.
What are Transverse dunes?
Transvers dunes are linear dunes that move perpendicular to the wind. Transverse dunes require a large supply of sand and constant wind.
What are the 5 types of sand dunes?
Transverse - large supply of sand and constant wind. Barchan - supply of sand is limited and winds moderate. Linear, longitudinal or seif dunes- long parallel ridges of sand, occur where strong prevailing winds converge and blow in a constant direction with a limited supply of sand. (Look like worms) Star Dunes- mounds of sand having a high central point with 3 or 4 arms or ridges radiating out (typical of N. Africa and Saudi Arabia) formed from winds blowing in 3 or more directions. Parabolic dunes (blowouts) - develop along cosatlines where vegetation partly covers a ridge of wind-blown sand