Star dunes: Shrouded in beauty and wonder, they are now a bit less mysterious
Sand dunes shape some of the most fascinating scenery on Earth, particularly in arid regions. Among them, star dunes – sometimes called pyramid dunes – stand out for their towering height and eye-catching form.
Sand seas, located in places like Africa, Arabia, China, and North America, are home to these beautiful, star-like formations.
Star dunes form in areas where wind arrives from multiple directions and where sand accumulates in large quantities.
They have a tall, pyramid-like center with several arms spreading out, creating a star shape when seen from above.
Some reach extraordinary heights, including one in China’s Badain Jaran Desert that measures about 984 feet, placing it on par with a famous landmark in Paris.
Star dunes and the geological record
Despite being common in modern deserts and even appearing on Mars and Saturn’s moon Titan, they have been unusually difficult to find in the geological record.
Researchers have often wondered why these dunes leave so little trace in old sandstone layers.
Professor Geoff Duller, from the Department of Geography and Earth Sciences at Aberystwyth University, has been at the forefront of investigating these hidden giants.
His latest study, undertaken alongside collaborators at Birkbeck and University College London (UCL), offers new insights into the internal structure and speed of formation of a star dune in Morocco.
This research helps explain why geologists have had trouble identifying these dunes in ancient deposits.
Hidden patterns in the Sahara
Until now, star dunes received limited attention compared to other well-known dune varieties. The recent study in the Erg Chebbi region of southeastern Morocco reveals a star dune named Lala Lallia, meaning “highest sacred point” in the Berber language.
It rises about 328 feet and stretches about 2,297 feet across its base. Scientists found that its oldest layers date back roughly 13,000 years, around the time of the Younger Dryas, a sudden cooling phase in Earth’s past.
Ground-penetrating radar scans show that the dune remained mostly dormant for about 8,000 years.
Pottery discovered nearby suggests wetter conditions, possibly driven by an expanded monsoon, that kept sand from piling up. Once drier weather arrived, sand began accumulating at a much faster pace.
The results, published in the journal Scientific Reports, indicate that the dune gained most of its size in the last thousand years and is currently shifting westward at about 1.6 feet each year.
Radar and luminescence offer clues
“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,” explained Professor Charlie Bristow of Birkbeck and UCL.
Researchers also used optically stimulated luminescence (OSL) dating to determine when minerals in the sand were last exposed to sunlight.
This approach made it possible to figure out precisely when the dune began building after the African Humid Period had ended.
The study concludes that large star dunes may form far more rapidly than many geologists once assumed.
“This research is really the case of the missing sand dune – it had been a mystery why we could not see them in the geological record. It’s only because of new technology that we can now start to uncover their secrets,” noted Professor Duller.
“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 50 cm a year. These fantastic star dunes are one of the natural wonders of the world.”
Star dunes and ancient deserts
The discovery sheds light on why star dunes appear absent in older rocks. Their internal layers can mimic those of other dune types, making them hard to recognize once they have turned to stone.
This new model, drawn from the Moroccan site, gives geologists a better guide for identifying similar formations preserved deep underground.
“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,” Professor Duller added.
“They are giving us insight into geology that could have wider implications including geological deposits that are used for water resources and storing carbon.”
Tracking the shifting winds across eons
Experts note that changes in wind direction contributed to the dune’s star-like shape. As the desert climate became drier, gusts from different angles helped shape the steep pyramid center and radiating arms.
The speed with which it gained height shows that dramatic environmental shifts can build a towering dune in a geologically short window.
Researchers also point out that similar wind shifts might have influenced dunes in other deserts worldwide.
Why star dunes matter
To sum it all up, star dunes hold importance for the study of past environments. The tools and findings from Morocco offer a chance to spot these features in buried sandstone layers.
That means geologists can learn more about the behavior of ancient winds, as well as periods of relative stability or intense dryness.
Understanding these long-past climatic patterns might help in present-day attempts to manage water in desert regions.
Studying how star dunes grow in modern deserts could open new avenues for interpreting desert rocks of the past.
By pinpointing signs of varied wind directions, geologists gain a clearer picture of what conditions shaped Earth’s surface thousands of years ago.
With fresh ways to identify these pyramidal giants in ancient layers, scientists are better equipped to find the missing chapters of desert history.
The full study was published in the journal Scientific Reports.
—–
Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.
—–
