deserts-wind.ppt

This slides has covered deserts, deserts dunes how it forms.

1. DESERTS AND WIND
ACTION

2. 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

3. Desert (arid climate) and
steppe (semiarid climate) areas on Earth
DESERTS AND WIND ACTION

4. DESERTS AND WIND ACTION
•Wind erosion processes
•deflationis the removal of rock waste from
the land by the wind
•blowout or deflation hollowis 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

5. Blowout or deflation hollow
DESERTS AND WIND ACTION

6. DESERTS AND WIND ACTION
Deflation Hollow---Blowout

7. abrasionis the “sandblasting”effect
on materials caused by the impact
with particles carried by the wind—
frosted windows in houses and
ventifactsform
DESERTS AND WIND ACTION

8. 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 loesslacking layering
or stratification

9. DESERTS AND WIND ACTION
Dust Storms

10. DESERTS AND WIND ACTION
Loess Deposits

11. 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

12. Dune profile
DESERTS AND WIND ACTION

13. 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

14. Barchan dunes
DESERTS AND WIND ACTION

15. DESERTS AND WIND ACTION
•transverse
•elongated perpendicular to direction of
wind
•formed with a constant direction of wind
and large supply of sand

16. DESERTS AND WIND ACTION
•longitudinal or seif
•elongated in general direction of wind
•formed with slightly different wind
directions and limited sand supply

17. DESERTS AND WIND ACTION
•star or complex
•formed with variable wind direction

18. 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

19. a bajada is an apron of sediment
resulting from a coalescence of
alluvial fans
DESERTS AND WIND ACTION

20. 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

21. 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

22. DESERTS AND WIND ACTION
•Pediment
•a carved gently sloping erosional surface on
the bedrock in a desert mountainous area

23. Stages of landscape in mountainous desert regions
DESERTS AND WIND ACTION

24. 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

25. THAT’S ALL THE
CYBER GEOLOGY
COURSE FOLKS