Researchers unravel the secret of the planet’s greatest desert sands

For the first time, the age of one of the biggest and most intricate varieties of sand dunes on Earth has been determined. Star dunes, sometimes known as pyramid dunes, are hundreds of meters high and are named for their unique formations. They can be discovered on Mars, in Africa, Asia, and North America, but their formation date has never been determined by researchers. Researchers have now found that the Lala Lallia dune in Morocco developed 13,000 years ago. Opposing winds that shift direction form star dunes. According to Prof. Geoff Duller of the University, knowing their age helps scientists comprehend those winds and break down the climate of that era.

 

Situated on the Erg Chebbi sand sea in southeast Morocco, Lala Lallia is named after an indigenous Amazigh place name meaning the highest sacred spot. Radiating arms around its 700 m wide, 100 m high form. It stopped growing for approximately 8,000 years after it first formed, and in the last few thousand years, it has rapidly expanded again. In Earth’s geological past, deserts are typically identifiable, but up to now, star dunes have not been found. Professor Duller speculates that this could be because the dunes are so big that the experts were not aware they were observing a single, distinct dune.

 

“These findings will probably surprise a lot of people as we can see how quickly this enormous dune formed, and that it is moving across the desert at about 50cm a year,” he says. The age of the star dune was determined by the scientists using a method known as luminescence dating. The technique determines the last time the sand grains were exposed to light. Sand samples from Morocco were collected in the dark, and they were examined in a lab under dim red light, akin to that of a traditional photography workshop. The mineral granules in the sand are referred to by Prof. Duller as “little rechargeable batteries”. The energy that the crystals contain is derived from radioactivity found in the surrounding environment.

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