How Old Are the Dunes? Researchers Reveal Age of Earth's Largest Sand Sea

Star or pyramid dunes found in Africa, Asia, North America and even the planet Mars are so-named for their unique shapes, but until recently experts had been unable to work out their age.

New findings reveal that the formation of the Lala Lallia sand dune in Morocco dates back 13,000 years.

Lala Lallia, a major feature in Morocco's Erg Chebbi sand sea, stands 100 meters high and spans 700 meters wide.

According to research published in the journal Nature, its size remained static for roughly 8,000 years after its formation before experiencing rapid expansion over the past several millennia.

Pyramid dunes are formed in areas with multidirectional winds. Professor Geoff Duller from the University of Aberystwyth in Wales, who co-authored the study, said determining dune's age would help researchers understand the forces that create them and also the climate of that historical period.

Duller and his co-researcher Professor Charles Bristow from Birkbeck University in London, worked out the age of the star dune using the luminescence technique to calculate when its sand grains were last exposed to daylight. They collected sand samples from Morocco and analyzed them in a lab under dim red lighting, reminiscent of a photograph developing studio.

Professor Duller likened the mineral grains in the sand to "little rechargeable batteries" that store energy from natural radiation. As the sand remains buried underground, it accumulates more radioactivity and energy. When exposed in the lab, the grains release energy as light, allowing scientists to evaluate their age.

Earth’s biggest pyramid dune is found in the Badain Jaran desert, spanning the Chinese provinces of Gansu, Ningxia, and Inner Mongolia. It reaches a height of over 1,600ft (over 500m). Star Dune and Hidden Dune in the US state of Colorado are two tallest in North America, measuring 741ft (225m) from bottom to peak. Others include Algeria’s Grand Erg Oriental and Grand Erg Occidental, Namibia’s Namib Sand Sea and Saudi Arabia’s Rub’ al Khali.