The age of one of the largest and most complex types of sand dunes on Earth has been calculated for the first time, writes the BBC.
Star dunes - or pyramidal dunes - are named for their characteristic shapes and reach hundreds of meters in height.
They have been found in Africa, Asia and North America, as well as on Mars - but experts have never before been able to determine when they were formed.
Now scientists have discovered that a dune named Lala Lalia in Morocco was formed 13.000 years ago.
According to the BBC, star dunes are created by opposite winds that change direction. Understanding their age helps scientists understand those winds and work out the climate at the time, says Professor Geoff Duler of Aberystwyth University, who published the research with Professor Charles Bristow of Birkbeck University.
Lala Lalia (indigenous Amazira name meaning "highest holy point") is located in the sandy sea of Erg Chebi in southeastern Morocco. It is 100m high and 700m wide with arms spreading like a star.
After its initial formation, it stopped growing for about 8.000 years and then expanded rapidly in the last few thousand years.
Usually, deserts can be identified in Earth's geological history, but so far not star dunes.
Professor Duler says this may be because they are so large that experts did not realize they were looking at a separate dune.
"These findings will probably surprise a lot of people, because we can see how quickly this huge dune formed and that it is moving across the desert at about 50 centimeters a year," he adds.
Scientists used a technique called "luminescence dating" to determine the age of the star dune.
The method calculates when the grains of sand were last exposed to daylight.
"Sand samples were taken in the dark from Morocco and analyzed in a laboratory under low red light conditions similar to an old-fashioned photography workshop," the BBC said.
Professor Duler describes the mineral grains in the sand as "small rechargeable batteries". They store energy within the crystal that comes from radioactivity in the natural environment.
The longer the sand is buried underground, the more it is exposed to radioactivity and the more energy it accumulates.
"When the grains are exposed in the laboratory, they release energy in the form of light and scientists can calculate their age," according to the BBC.
"In our dark laboratory, we see light from these sand grains. The stronger the light, the older the sediment grains are and the longer they have been buried," says Professor Duler.
Other examples of these huge dunes include Star Dune in Colorado, North America, which is the tallest dune in the United States, measuring 225m from base to top.
Climbing these dunes is hard work, Professor Duler explains. "When you're climbing, you go up two steps and slide back down one. But it's worth it – they're absolutely beautiful from the top," he says.
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