The Desert system
1. Locations and names
Some names of landforms and features
Ripples and Dunes
• Ergs (sand seas)
• Yardangs (erosional ridges)
• Hoodoos (erosional pillars)
• Desert pavements (deflation lag)
• Ventifacts
Bedforms
• Ballistic ripples and ridges
• Dunes
Airflow over dunes
Grain fall and grain flow processes
Grain fall occurs as saltating grains on the stoss slope fly over the
brink and come to rest on the lee face.
Grain flow occurs as the upper lee face steepens from grainfall
accumulation and then fails to static angle of repose.
Grain fall and grain flow processes
Ripples can occur as ornamentation on lee face.
Slumps occur only on wet dunes, because cohesion is needed.
Classification of dunes
The generation of cross-sets and sequences
For accumulation to occur, flux in must exceed flux out, q
i
> q
o
Generation of a sequence of beds
Wet aeolian system. Accumulation
with a rising water table with time.
