Deserts are defined as regions that receive less than 10 inches of annual precipitation. They cover about one fifth of the Earth's surface and can form due to factors like proximity to mountain ranges, prevailing winds, and ocean currents. Common landforms in deserts include alluvial fans and playa lakes. Erosion processes shape desert landscapes through wind erosion like deflation and abrasion, as well as flash floods when rain does occur. Wind also forms various dune types like barchan and longitudinal dunes from sand transport.

1. Deserts

3. Deserts: definition
• A region which has an arid climate or where
evaporation exceeds precipitation
• Steppe: region often adjacent to a desert
• Semiarid climate: irregular precipitation,
enough to generate minimal plant growth

5. Desert and Steppe areas
around the world:

6. Deserts:
• Cover a fifth of the
earth’s surface
• Can be found at all
altitudes and
latitudes
• Four physical factors
cause deserts : all
are influenced by
prevailing winds
a. Continentality
b. Lee side of
mountains
c. Cold ocean currents
d. Prevailing winds

7. Prevailing Winds:
• Found 30 n and s latitude due to the
global wind circulation system
• Descending air masses are
compressed, warm and absorb
moisture

9. Lee Side:

10. Coastal Location:

11. Desert Erosion: Water
• Seldom rains in desert regions
• When it does massive DOWNPOUR or it’s
called a FLASHFLOOD
• Dry weathered soil, and minimal vegetation to
anchor the soil causes rapid erosion
• Rainwater carries sediment away and
deposits it on the valley floor
• Within 10 to 20 minutes the rain is gone and
the water has evaporated

14. Wind erosion processes:
• Deflation ; is the removal of rock waste
from the land by wind
– Blowout or deflation hollow ; depression
caused by deflation due to lack of
vegetation to hold material down

15. Landforms: created by water
• Alluvial Fan:
• Fan shaped delta
formed at the foot of
mountains in a
desert valley
• A Bajada is an apron
of sediment resulting
from a coalescence
of alluvial fans

17. Landforms : water
• Playa Lake:
– A temporary shallow
lake formed in the
central basin of a
desert during a rare
downpour
– A Playa is the dry flat
lake bed that
remains

19. Wind erosion processes:
• Deflation: removal of
rock waste from the
land by the wind
• Abrasion :
“sandblasting” effect
on materials caused
by the impact with
particles carried by
the wind

20. • Bedload:
– Saltation
– Suspension
– Particles are bounced
along the ground or
suspended in the air;
both these process erode
rock surfaces and carry
material

21. Sand Dunes:
• Many different types
but learn these:
• Barchan: crescent
shaped with convex
portion facing the
wind
• Formed with a
constant wind and
limited sand supply

22. • Longitudinal or seif
• Elongated in general
direction of wind
• Formed with slightly
different wind
directions and
limited sand supply

23. Inactive or stable dune:
• Parabolic Dune:
• Formed along
coastlines or large
lakes
• Winds cause
blowouts in sand
resulting in a
crescent shape with
convex side facing
the wind

24. Reg Deserts: little sand