Erg deserts

From GeoClasses

The Grand Occidental Erg in the Sahara Desert. http://disc.gsfc.nasa.gov/geomorphology/GEO_8/GEO_PLATE_E-4.HTML

Erg Deserts are large compilations of sand, they are often referred to as sand seas or desert seas. Ergs are plains of sand that have accumulated over thousands of years. In order to be called an Erg Dessert the area must be at least 125 km², if the area is smaller they are just called sand dunes. These deserts can stretch for hundreds of miles and heights can reach 1,000 feet. The Grand Erg Occidental and Oriental are located in Algeria; the Selima Erg covers more than 3,000 square miles in Libya; the Erg Cherch goes for 600 miles across Mali and Algeria.

Picture taked from a space shutte. Shows the dunes of the Grand Erg Oriental. http://disc.gsfc.nasa.gov/geomorphology/GEO_8/GEO_PLATE_E-6.HTML

1 Location/ Climate
- 1.1 The Main Erg Deserts are:
2 Formation of Erg Deserts
3 Exam Question:
4 Sources:

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Location/ Climate

Erg Deserts occur in hot dry climates. The descending air of the subtropical high warms the area causing the air to dry out reducing chances of condensation. They usually occur down wind and are typically a source of dry, loose sand in riverbeds and deltas or dried up lakes. Most desert seas are in large basins that at one time contained shallow rivers or lakes. There is very little rainfall each year if any the rivers and lakes dry up. Because of this, these areas have accumulated sediment deposit. The sand which makes up the ergs is constantly being built up and eroded by the wind.

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The Main Erg Deserts are:

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The Grand Occidental and Oriental Ergs

The Grand Occidental and Oriental Ergs cover most of Algeria: The Grand Erg Oriental is the larger of these two ergs which dominate most of Algeria. The Grand Erg Occidental is the Eastern sand sea and the Grand Erg Oriental is the Western Sand sea of the Sahara. The sand in some areas of this desert is over 300m deep. These Erg deserts occupy over 20% of the Sahara Desert.

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The Erg Chebbi Dunes

The Erg Chebbi Dunes are in Morroco: The Erg Chebbi Dunes or Morocco stretch for about 20 Kilometers.These dune are known for their great hights, some more than 50 meters heigh.

The Erg Ubari and Murzuq in Libya from http://www.esrin.esa.it/export/esaEO/SEMJTWRMD6E_index_0.html

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The Erg Ubari and Murzuq in Libya

The picture to the right shows these two Ergs. The reddish sand sea at the top of the picture is the Erg Ubari.The lighter sand sea at the bottom is the Erg Murzuq.The dark area in the center of the picture separates the two.

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Formation of Erg Deserts

In deserts, wind erodes the land. The wind picks up loose sand sized sediment. The sediment is migrates down wind and is eventually slowed or stopped by a barrier such as rocks or hills. The sediment is then deposited creating oddly shaped peaks, grooves, and dunes. When several large dunes are created in one region (area larger than 125 km2) it is called an Erg Desert.