Transcript DESERTS AND WIND ACTION - Missouri State University

DESERTS AND WIND
ACTION
DESERTS AND WIND ACTION
• Desert regions and wind erosion
• Desert and adjacent region
• desert
• region which has an arid climate
• steppe
• region adjacent to a desert with semiarid
climate
DESERTS AND WIND ACTION
Desert (arid climate) and
steppe (semiarid climate) areas on Earth
DESERTS AND WIND ACTION
• Wind erosion processes
• deflation is the removal of rock waste from
the land by the wind
• blowout or deflation hollow is a depression
excavated by the wind in materials as sand
and silt deposits easily eroded because of a
lack of the presence of adequate vegetation
which impedes deflation
DESERTS AND WIND ACTION
Blowout or deflation hollow
DESERTS AND WIND ACTION
Deflation Hollow---Blowout
DESERTS AND WIND ACTION
abrasion is the “sandblasting”effect
on materials caused by the impact
with particles carried by the wind—
frosted windows in houses and
ventifacts form
DESERTS AND WIND ACTION
• Wind erosion loads
• suspended load
• suspended wind blown particles
• consists primarily of silt or clay size
particles and if highly concentrated can
result in dust storms
• deposition of the suspended load can result
in large deposits of loess lacking layering
or stratification
DESERTS AND WIND ACTION
Dust Storms
DESERTS AND WIND ACTION
Loess Deposits
DESERTS AND WIND ACTION
• bed load
• particles bounced along the ground
• usually consists of sand size particles
• accumulation of the bed load forms desert
sand dunes which can migrate
easily(active dunes)
• Active sand dunes
• Nature of active (unstable) dunes
• dune profile
• consists of a more gentle windward slope
and steeper leeward slope or slipface
DESERTS AND WIND ACTION
Dune profile
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• shifting dunes
• shift downwind and can bury roads, airport
runways, homes, etc.
• Categories of active dunes
• based on shape of dune in plan view
• barchan
• crescent shaped with convex portion
facing the wind direction
• formed with a constant wind direction and
limited sand supply
DESERTS AND WIND ACTION
Barchan dunes
DESERTS AND WIND ACTION
• transverse
• elongated perpendicular to direction of
wind
• formed with a constant direction of wind
and large supply of sand
DESERTS AND WIND ACTION
• longitudinal or seif
• elongated in general direction of wind
• formed with slightly different wind
directions and limited sand supply
DESERTS AND WIND ACTION
• star or complex
• formed with variable wind direction
DESERTS AND WIND ACTION
• Desert landscape and evolution
• Alluvial fan
• fan shaped deposit formed at the foot of
mountains in the desert valley or basin
DESERTS AND WIND ACTION
a bajada is an apron of sediment
resulting from a coalescence of
alluvial fans
DESERTS AND WIND ACTION
Playa lake and playa
a temporary shallow lake formed in the central
basin of a desert during a rare abundant
rainfall--a playa is the dry flat lake bed that
remains
DESERTS AND WIND ACTION
• Inselberg
• an isolated erosional remnant present after
long term erosion of mountain areas which
are reduced to these bedrock knobs elevated
above the surrounding sediment filled basin
DESERTS AND WIND ACTION
• Pediment
• a carved gently sloping erosional surface on
the bedrock in a desert mountainous area
DESERTS AND WIND ACTION
Stages of landscape in mountainous desert regions
DESERTS AND WIND ACTION
• Inactive or stable dune---mostly non-desert
• Parabolic dune(foredune)
• formed along coastlines of oceans or large
lakes
• winds cause blowouts in sand resulting in a
crescent shape with the concave side facing
the prevailing wind direction
THAT’S ALL THE
CYBER GEOLOGY
COURSE FOLKS