Chapter 28, Problem 20RQ

To determine

The process of migration of sand dunes.

Answer to Problem 20RQ

Sand dunes migrate when grains on the windward slope are blown up and over the crest of the dune falling on the leeward slope. This process repeats and over the time entire dune moves.

Explanation of Solution

Wind transports and deposits sediment such as sand grains. When the speed of wind carrying sand grains is obstructed by an obstacle such as a rock or a bunch of vegetation, then the speed of wind drops. Due to this the sand grains settle down where the wind is blocked. When more and more sand gets settle down then the mound grows into a dune. This dune is called sand dune. With more wind and more sand, the dune grows and begins to move downwind. Sand dunes migrate when grains on the backside slope are blown up and over the crest of the dune falling on the front slope. This process repeats and over the time entire dune moves.

Conclusion:

Therefore, the sand dunes migrate when grains on the windward slope are blown up and over the crest of the dune falling on the leeward slope.