Browse image
Resolutions offered for this image:
1000 x 664 pixels 540 x 359 pixels 540 x 405 pixels 3072 x 2098 pixels 640 x 437 pixels
Cloud masks available for this image:

Spacecraft nadir point: 26.6° N, 4.7° E

Photo center point: 26.3° N, 6.9° E

Nadir to Photo Center: East

Spacecraft Altitude: 184 nautical miles (341km)
Click for Google map
Width Height Annotated Cropped Purpose Links
1000 pixels 664 pixels No Yes Earth From Space collection Download Image
540 pixels 359 pixels Yes Yes Earth From Space collection Download Image
540 pixels 405 pixels Yes Yes NASA's Earth Observatory web site Download Image
3072 pixels 2098 pixels No No Download Image
640 pixels 437 pixels No No Download Image
Other options available:
Download Packaged File
Download a Google Earth KML for this Image
View photo footprint information
Image Caption: Tifernine Dune Field, Algeria

The Tifernine Dune Field is located at the southernmost tip of the Grand Erg Oriental, a "dune sea" that occupies a large portion of the Sahara Desert in eastern Algeria. This astronaut photograph illustrates the interface between the yellow-orange sand dunes of the field and dark brown consolidated rocks of the Tinrhert Plateau to the south and east (image right). Three distinct landforms are visible in the image, each providing information about past and present climate in the area.

The oldest landform is represented by the rocks of the Tinrhert Plateau, where numerous channels incise the bedrock; these channels were eroded during a wet and cool climate period, most probably by glacial meltwater streams. As the dry and hot climate that characterizes the Sahara today became established, water ceased to flow in these channels. Winds eroded and moved large amounts of drying sediment (sand, silt, and clay), which piled up in large, linear dunes that roughly parallel the direction of the prevailing winds of the time (image center).

The present climate is still hot and dry, but current wind directions are more variable. The variable winds are modifying the older, linear dunes, creating star dunes, recognizable by a starfish-like pattern when seen from above. White to grey regions within the dune field are exposed deposits of silt and clay, together with evaporite minerals (such as halite, or common table salt) formed by evaporation of water that collected in small basins between the dunes.