Scientists have calculated the age of a star dune for the first time, solving a mystery in Earth’s geological record.
The dunes, so-called because they look like stars from above, with arms that spread out in several directions from a central peak, are found in deserts across the world, including in the UAE.
They are also found elsewhere in the solar system – on Mars and on Saturn’s moon Titan.
However, they have rarely been described in records, despite having featured in past deserts preserved in rocks deep underground.
The study by Aberystwyth University, Birkbeck and University College London academics is the first to date how long it took a star dune to form and examine its internal structure.
Using a technique that dates the last time minerals in the sand were exposed to sunlight, they determined that the Lala Lallia dune in south-east Morocco formed 13,000 years ago.
The research suggests the dune reached its 100-metre height and 700-metre width due to rapid growth in the past 1,000 years as it shifted slowly to the west.
Prof Geoff Duller, from the department of geography and Earth sciences at Aberystwyth University, which was involved in the study, said the research finally solves the case of the “missing sand dune”.
He told The National: “One of the odd things is, today, if you look around the world, including in the UAE in the Liwa [Empty Quarter] desert, there are some fabulous star dunes. They are quite common.
“But when you look in the geological record – and these deserts produce some fabulous geology that’s really important for water, aquifers, for gas and oil storage – we can only find a record of one place where someone has described a star dune.
“I think part of it is no one really knew what to look for.”
Prof Duller said it is only because of new technology – and a process called luminescence dating – that scientists can now start to uncover their secrets.
“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. These fantastic star dunes are one of the natural wonders of the world.”
Believed to be the tallest dunes on Earth – with one in the Badain Jaran Desert in China reaching 300 metres – star dunes are widespread in most deserts, including in Africa, the Middle East, China and North America.
On the Arabian peninsular, they are common in the Empty Quarter, also known as the Rub Al Khali, which covers an area of about 660,000 square km.
The Empty Quarter, a vast sand sea is the largest continuous sand desert on Earth, stretching from southeastern Saudi Arabia, where it occupies a quarter of the country’s land mass, with lesser portions in Yemen, Oman and the UAE.
To form, they need a lot of sand and opposing winds.
Lala Lallia sits in the Erg Chebbi area of the Sahara, close to the border with Algeria, an area featured in TV series such as SAS Rogue Heroes and blockbuster films such as The Mummy and Sahara.
Prof Charlie Bristow of Birkbeck and UCL added: “Using ground penetrating radar to look inside this star dune has allowed us to show how these immense dunes form, and to develop a new model so geologists know better what to look for in the rock record to identify these amazing desert features.”
Their research suggests the star dune formed at around the same time as the Younger Dryas event, an abrupt cooling period in Earth’s history.
It also reveals that the dune stopped growing for 8,000 years – possibly due to wetter conditions caused by an enlarged monsoon, suggested by the presence of pottery at the site, that stabilised the dune before the onset of a great drought.
The study used luminescence dating techniques developed at Aberystwyth University to discover the last time minerals in the sand were exposed to sunlight to determine their age.
“It’s quite a privilege to think that the luminescence dating techniques developed here in Aberystwyth are unlocking some of the secrets of the most challenging climates in the world,” said Prof Duller.
“They are giving us an insight into geology that could have wider implications, including geological deposits that are used for water resources and storing carbon.”
