Chapter 15: Eolian Processes and Arid Landscapes
Wind is a geomorphic agent just as water is. Wind works to erode, transport, and deposit
sediments.
Eolian The transport of sediments by the wind.
Deflation The removal and
lifting of individual loose particles.
Desert Pavement A concentration of pebbles and gravel that is left after the fine
particles are removed by the wind.
Blowout Depression A basin that is formed from removal of
fine sediment by the wind.
Abrasion The grinding of
rock surfaces by sandblasting.
Yardangs Streamline landforms that have been sculpted by the wind.
Saltation
Wind transport of particles by
bouncing them along the ground.
Suspension Wind transport
of fine particles in the wind.
Surface creep Movement of particles that slide or roll along the surface, pushed by the force of wind.
Ripples The smallest
landform shaped by the wind. Ripples
form in crests and troughs and are positioned at right angels to the direction
of the wind.
Dunes Similar in shape to
ripples, these are larger in scale and are the main feature that we associate
with deserts.
Slipface
A steeply sloping surface on the lee side of the dune.
Windward slope Gently sloping surface that faces into the wind.
Dune Classification
Cresentic Curve shaped dunes
Barchan Crescent shaped
dunes with horns pointing downwind.
Unidirectional wind flow and little sand available.
Transverse Asymmetrical
ridge at right angles to the wind direction.
Results from light winds and a large supply.
Parabolic Open end faces
the wind; the arms of the dune are stabilized by vegetation.
Barchanoid Ridge A wavy
asymmetric dune ridge formed at right angles to strong winds.
Longitudinal Long, slightly
sinuous, ridge shaped dune aligned parallel to the wind direction. Has 2 slipfaces. Results from strong but slightly varying winds from the same
general direction.
Seif Moderately sinuous
ridge shaped dunes that are shorter than longitudinal dunes. Rounded end upwind and pointed end downwind.
Star Dune Formed by a changing wind pattern, they
have multiple slipfaces and radiating arms that rise to form a central-tall
peak.
Dome Circular or
elliptical mound with no slipface.
Reversing Asymmetrical
ridge form intermediate between star dune and transverse dune.
Desert Climates Occupies 35% of the Earths land
surface. Characterized by low
precipitation and high potential evapotranspiration levels driven by high
temperatures.
Desert Fluvial
Processes Precipitation in desert regions is low but it often comes very
quickly.
Flash Flood A sudden
flood caused by high amounts of rainfall in the watershed of a river. Flash floods can occur in what is normally a
dry riverbed.
Wash A dry streambed also
called an arroyo.
Playa An intermittently
wet lakebed. These areas form evaporite
deposits of different salts.
Alluvial Fan A fan of
sediment that forms at the mouth of a canyon.
Bajada A continuous apron
of debris along the foot of a mountain range.
These form when individual alluvial fans merge.
Hoover Dam completed in 1930.
Glen Canyon Dam completed in 1963.
Water discharge and
the allotment for the seven states and two countries involved were measured
between 1914-1923.
Tree-ring research demonstrated that this period of record happened to
be the wettest period in the last 400 years.
So the amount of water allotted to each state cannot be fulfilled in a
normal year.
The Basin and Range Province is a unique portion of the western United States. This region is situated in a dry climate on
the leeward side of Sierra Nevada Mountains.
This region used to have a spreading center underneath it so it
responded to tensional forces forming horst and graben topography.
Desertification Expansion of the Earths desert lands due
principally to overgrazing and poor agricultural practices. The UN estimates that deserts have spread
covering 2 billion more acres than they used to in the 1930s.