Natural causes? Erosion, from wind and water.

Question

http://geography.about.com/od/physicalgeography/a/erosion.htm

I cannot seem to find any specific natural causes of sand deposition. I have read all of my chapters and google searched "sand deposition" and can't get anything useful. Please help.

Erosion from wind and water causes it to break down into minerals and popssibly decompose. I had the same question on a science test I got it right. but as for you it might not be.