Geoscience Reference
In-Depth Information
10.0
1.0
0.1
Threshold
velocity
(m/sec)
0.01
0.001
0.0001
0.00001
0.000001
Clay
<0.002 mm
0.0008 in
Silt
0.002-0.05 mm
0.0008-0.002 in
Sand
0.05-2.0 mm
0.002-0.08 in
Figure 18.11 Threshold velocities required for wind to carry various-sized particles.
The largest sand particles require a
wind velocity of 10 m/sec (∙33 ft/sec) to be moved by the wind.
Relative
wind speed
Long-term
suspension
(< 0.02 mm)
Short-term
suspension
(0.02-0.07 mm)
Surface
creep
(> 0.5 mm)
Saltation
(0.07-0.5 mm)
Turbulence
Wind
4
3
Bouncing
particles
2
1
0
Surface of loose sand
Pebbly surface
Figure 18.12 Transportation of eolian sediment.
Windblown sediment can move by suspension, by saltation, or by surface
creep. Note the flow lines to visualize how these processes operate.
