Simple facts
Where is it? Grand Elgu Oriental, Sahara [30.13306820, 9.306920931]
What do you see in the photo? The stardunes field meets Rocky Hills
Which satellite took the photo? Earthkam camera rides on the International Space Station
When did you take it? October 31, 2017
This impressive satellite image shows the harsh difference between a huge field of sandy “stars” in the Sahara Desert and a barren, rocky wilderness. The contrasting biomes overlap with the borders that the two African countries meet.
The sea of orange sand seen in this image is part of the Grand Erg Oriental. This is a huge field of sand dunes or ERGs covering approximately 55,000 square miles (140,000 square kilometers) of the northern Sahara.
This part of the ERG contains hundreds of prominent “Star Dunes”, with at least three ridges from the central peak, giving it a star-like appearance when viewed from above. Star dunes grow above 300 feet (90 meters) tall and can only form in places where wind directions change constantly, according to the National Park Service.
You might like it
According to NASA’s Earth Observatory, the dunes are “the driest part of the Sahara Desert” and overlap with wind-blowing rocky terrain that is almost completely lacking vegetation. The topography is covered with geological features, giving it another world quality.
One of the most striking features is the large white patches in the heart of rocky terrain, remnants of the ancient lake. You may also be able to see a series of parallel grooves on the rocks carved for years, with unsolved winds blown away long before the multifaceted dunes formed.
Related: See all the best images of Earth from Space
All the dunes in the image are located within Algeria, with most of the rocky terrain being in Libya. The invisible boundary between the two countries is primarily at the very center of this image. But at one point it’s right to the left of the town of Libyan, known as Gadams (seems as a dark place near the top of the image), and the border between the countries overlaps almost exactly with the lines where sand and rock meet.
The contrasting ecosystems seem to have nothing to do with each other, but are more linked than you might imagine. Geologists believe that much of the ERG sand was deposited by ancient rainwater, taking loose sediments from rocky terrain and abandoning them to natural depression or sinking in the landscape.
This process probably took hundreds of thousands, if not millions, but if you look closely you can see that some of the ERG sand has returned to the ancient “take-up water course” that helps to deposit the ERG sand within the ERG.
The ERG is partially formed on an ancient river bed. As rain settles on the sand of the erg, moisture can leak into the underground aquifer, allowing the surface vegetation pockets to support. If this does not happen, this precious water will quickly return to the atmosphere and evaporate.
Source link
