Author Question: How do dunes build their characteristic asymmetrical profile? What will be an ideal ... (Read 64 times)

rmenurse · **on:** Jul 15, 2018

How do dunes build their characteristic asymmetrical profile? What will be an ideal response?

Question 2

Why do dunes form? How are they self-generating? What will be an ideal response?

cloudre37 · **Reply #1 on:** Jul 15, 2018

Answer to Question 1

Most dunes have an asymmetrical profile with a gentle windward slope and a steeper leeward slope
that is included in the direction of the prevailing wind. Sand grains move up the gentle windward slop
by saltation and accumulate on the leeward side, forming an angle of 30 to 34 degrees from the
horizontal, which is the angle of repose of dry sand. When the angle is exceeded by accumulating
sand, the slope collapses, and the sand slides down the leeward slope, coming to rest at its base. As
sand moves from the dune's windward side and then slides down the leeward slope, the dune migrates
in the direction of the prevailing wind.

Answer to Question 2

Dunes form when wind flows over and around an obstruction, resulting in the deposition of sand
grains, which accumulate and build up a deposit of sand. As they grow, they form ever-larger wind
barriers that further reduce the wind's velocity, resulting in more sand deposition and growth of the
dune.