Scientists have solved the mystery of the mysterious absence of “star dunes”, star-shaped sand dunes, from Earth’s geological history for the first time, dating back thousands of years.
The study was conducted by academics from Aberystwyth, Birkbeck and University College London, and is the first of its kind to date to examine how long it took sand dunes to form these structures and examine their internal structure.
Star dunes are huge mountains named after arms extending from a central peak that look like stars when viewed from above.
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These dunes are very common in modern deserts, including the "Great Sand Seas", which are areas of sand dunes found in Africa, the Peninsula, China and North America, and are also found on Mars and on Saturn's largest moon, Titan.
However, it has never been found in the geological record of Earth's history. Its absence has confused scientists because former deserts were a common part of Earth's history, and they are preserved in rocks deep underground.
In the new study, published in the journal Scientific Reports, scientists focused on stellar sand dunes in a remote area in southeastern Morocco known as “Lalla Lalia,” which means “the highest sacred point” in the Berber language, and found that the oldest parts of the dunes are 13,000 years old. But they were surprised that the upper part of the structure had only formed in the past thousand years or so.
The sand dunes are located in the Erg Chebbi region (sand dunes in the Merzouga Desert in southeastern Morocco) in the Sahara Desert near the border with Algeria, an area that has appeared in television series such as SAS Rogue Heroes and films such as The Mummy and Sahara.
The research shows that the “sand pyramid” reached its current height of 100 meters and width of 700 meters due to rapid growth in the past thousand years as it slowly shifted westward.
Professor Geoff Dowler, from the Department of Geography and Earth Sciences at Aberystwyth University, said: “These results are likely to surprise many people, as we can see how quickly these massive sand dunes were forming, and that they are moving across the desert at around 50cm per year. These are extraordinary things. "It is one of the natural wonders of the world. From the ground, it looks like pyramids, but from the air you see a peak, and these arms branch out from it in three or four directions, which make them look like stars."
Professor Charlie Bristow, from Birkbeck and University College London, added: “Using ground-penetrating radar to look inside these stellar dunes has allowed us to show how these massive dunes formed, and develop a new model so that geologists will better know what to look for in the rock record to identify these Amazing desert features.
Advanced research conducted by scientists indicates that the star dunes formed at approximately the same time as the Younger Dryas event, a sudden cooling period in Earth's history. It also reveals that the star dunes stopped growing for 8,000 years.
Pottery found at the site also indicates wetter conditions, and perhaps widespread monsoon winds, that stabilized the dunes before the onset of the great drought.
The study used fluorescence dating techniques developed at Aberystwyth University to discover the last time minerals in the sand were exposed to sunlight to determine their age.
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