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Age of One of Earth's Largest Sand Dunes Calculated

The age of one of our planet's largest and most complex types of sand dune has been calculated for the first time.

The Lala Lallia star dune in Morocco
The Lala Lallia star dune in Morocco | Credit: C Bristow

Star dunes - also known as pyramid dunes - are named after their distinctive shapes and reach hundreds of metres in height. They are found in Africa, Asia and North America - but experts had never before been able to put a date on when they were formed. Now scientists have discovered that a dune called Lala Lallia in Morocco formed 13,000 years ago.

Star dunes are created by opposing winds that change direction. Lala Lallia (an indigenous Amazigh name meaning highest sacred point) is located in the Erg Chebbi sand sea in south-east Morocco. It is 100m high and 700m wide with radiating arms. After its initial formation, it stopped growing for about 8,000 years and then quickly expanded in the past several thousand years.

The calculations were made by Prof Geoff Duller at the University of Aberystwyth with Prof Charles Bristow at Birkbeck University, using a technique called 'luminescence dating' to work out the age of the star dune. The method calculates when the grains of sand were last exposed to daylight.

Normally deserts can be identified in Earth's geological history, but star dunes were absent until now. Prof Duller says this may be because they are so large that experts did not realise they were looking at one 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 adds.

Other examples of these huge dunes include Star Dune in Colorado, North America, which is the joint-highest dune in the US, measuring 225m from base to top.


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