What is a dune?

A dune is a hill of sand built by winds. The winds blow a bit of sand and it settles then the wind blows again adding to the pile and this continues until a hill of sand has formed called a dune.

Characteristics of a Dune:

1) Occur in many sizes and shapes.

2) Most have a gentle slope on the windward side, where sand is being eroded away, and a steeper leeward side, where sand is deposited.

3) Movement of sand from one side to the other may result in the migration of the sand dune in the direction the wind is blowing.  

Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind. The valley or trough between dunes is called a slack. A "dune field" is an area covered by extensive sand dunes. Large dune fields are known as ergs.

Along Lake Michigan shores many Dunes are found. Silver Lake Dunes, Sleeping Bear Dunes and the Saugatuck Dunes are just three sand dunes near Grand Rapids. Dunes are found all over the world. 

Algeria's Grand Erg Oriental is one of the largest sea of dunes in the world. This portion of the vast Sahara Desert covers over 140,00 square kilometers in area. These predominantly linear dunes run north-south, with some complex dunes in the area as well.

The famous sand dunes at Great Sand Dune national Park in southern Colorado formed in a valley from ancient lake bed. Large quantities of sand remained in the area after the lake breached. Predominant winds blew the sands towards the nearby Sangre de Cristo mountains. Storm winds blew over the other side of the mountains towards the valley, causing the dunes to grow vertically. This resulted in the tallest sand dunes in North America at over 750 feet.

Only sparce lake grasses grow in the dunes because the soil is unstable.

Places Dunes are found are:

Great Sand Dunes National Monument, Colorado

Death Valley National Park, California

Sleeping Bear Dunes, Silver Lake Dunes and Saugatuck Dunes in Michigan

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