Figure 10.31: These beautiful rocks are crossbedded sandstones from the Canyons of the
Escalante in Utah. ( 28 )
something that beach house owners need to consider if they live near coastal sand dunes.
Once a sand dune becomes stabilized by vegetation, such as sea grasses, its migration will
stop. Beach goers need to be careful not to disturb these grasses when they go to and from
the beach.
Reducing Wind Erosion – Types of Sand Dunes
There are several different forms that sand dunes will take. The differences are due to the
amount of sand available to be moved, the character and direction of the wind and the
type of ground the sand is moving over. The most usual crescent shaped dune is called a
barchan dune(Figure10.32). This type of dune forms when there is an adequate amount
of sand being moved by constant winds that blow from one direction over hard ground. The
crescent shape will curve in the direction the wind blows. In an area of constant winds
with an abundant supply of sand, barchan dunes blend together into large scale sand ripples
calledtransverse dunes.Many coastal dunes are this type of dune. Desert areas that are
completely sand covered can join many transverse dunes together into a sand sea.
Star shaped dunes form in areas of constantly changing wind direction with enough sand for
dunes to form. They are called stars because several ridges of sand all radiate out from a
central point. Linear dunes form when there isn’t much sand and winds come together from
different directions. This type of dune forms long straight lines of sand that line up parallel
to the wind direction. Coastlines are places of steady winds and abundant supplies of sand.
Parabolic dunes form where some type of vegetation at least partly covers the sand. These
coastal dunes form a curved shape that curves into the direction of the wind. This probably
occurs as the central portion of sand is blown out, leaving a U-shaped curve of sand.