how sand dunes are formed
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A sand dune needs the following three things to form:
A large amount of loose sand in an area with little vegetation -- usually on the coast or in a dried-up river, lake or sea bed
A wind or breeze to move the grains of sand
An obstacle that causes the sand to lose momentum and settle. This obstacle could be as small as a rock or as big as a tree.
Where these three variables merge, a sand dune forms. As the wind picks up the sand, the sand travels, but generally only about an inch or two above the ground. Wind moves sand in one of three ways:
Saltation: The sand grains bounce along in the wind. About 95 percent of sand grains move in this manner.
Creep: When sand grains collide with other grains -- like clay or gravel -- causing them to move. Creep accounts for about 4 percent of sand movement.
Suspension: Sand grains blow high in the air and then settle. About 1 percent of sand moves this way.
A large amount of loose sand in an area with little vegetation -- usually on the coast or in a dried-up river, lake or sea bed
A wind or breeze to move the grains of sand
An obstacle that causes the sand to lose momentum and settle. This obstacle could be as small as a rock or as big as a tree.
Where these three variables merge, a sand dune forms. As the wind picks up the sand, the sand travels, but generally only about an inch or two above the ground. Wind moves sand in one of three ways:
Saltation: The sand grains bounce along in the wind. About 95 percent of sand grains move in this manner.
Creep: When sand grains collide with other grains -- like clay or gravel -- causing them to move. Creep accounts for about 4 percent of sand movement.
Suspension: Sand grains blow high in the air and then settle. About 1 percent of sand moves this way.
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Answer: These dunes form when complex wind patterns alternate direction and change the way sand is piled onto the dune. ... Weathering is the physical and/or chemical breakdown of surfaces due to wind, water, or ice. Erosion is the process of moving the broken down material from one place to another via wind, water, or gravity.
Explanation:
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