DESERTS AND WIND ACTION DESERTS AND WIND ACTION

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 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

DESERTS AND WIND ACTION • 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