| Constructive
forces are things that help our beaches. Sometimes they are natural.
Sand dunes are built up by the wind. They usually are tall. This
protects the land beside the beach so that the wind is not as strong
there. 
Whenever the wind blows up sand into a pile, this is called
deposition. The wind has deposited sand into a pile.
Other constructive forces are man-made.
Sometimes humans build sand dunes or plant trees to shelter the
beaches and inland places. Sometimes people can place large rocks
along the shoreline like those in the picture on our background.
These rocks keep sand from eroding.
If you want to learn more about
constructive forces, work through the activities on this site:
http://www.bcps.org/offices/lis/models/Forces/index.htm.
Pictures from
http://commons.wikimedia.org.
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