[ToC]

 

Chester R. Longwell and Richard Foster Flint, Introduction to Physical Geology

DIAMETERS AND DISTRIBUTION OF ROCK PARTICLES CONSTITUTING THE LOAD OF A STREAM OF AIR

 

 

Wind velocity increases from the ground upward, quite steeply through the first few feed and then less steeply. Hence air pressure, being inversely proportional to velocity (Bernoulli's law), decreases from the ground upward. A sand grain lying on the ground will therefore have less pressure at the level of its upper surface than at its under surface. If the pressure difference is greater than the downward pull of gravity, the sand grain will rise. Moving air, like a stream of water, has a bed load and a suspended load. The bed load is close to the ground at all time; thus in desert areas telephone poles have been cut through by blowing sand, but always close to their bases; to prevent cutting, stones are plied around the pole bases.