عربي English Türkçe اردو فارسى
Logo
Latest News
Varieties

Scientists Reveal Secrets of Desert Star Dunes

A view of the Lala Lallia star dune of the Sahara Desert, in Erg Chebbi, Morocco, as seen in an undated handout image from 2008 and obtained by Reuters on March 1, 2024. Charlie Bristow/Handout via REUTERS
A view of the Lala Lallia star dune of the Sahara Desert, in Erg Chebbi, Morocco, as seen in an undated handout image from 2008 and obtained by Reuters on March 1, 2024. Charlie Bristow/Handout via REUTERS
TT
20
TT

Scientists Reveal Secrets of Desert Star Dunes

A view of the Lala Lallia star dune of the Sahara Desert, in Erg Chebbi, Morocco, as seen in an undated handout image from 2008 and obtained by Reuters on March 1, 2024. Charlie Bristow/Handout via REUTERS
A view of the Lala Lallia star dune of the Sahara Desert, in Erg Chebbi, Morocco, as seen in an undated handout image from 2008 and obtained by Reuters on March 1, 2024. Charlie Bristow/Handout via REUTERS

They are among the wonders of our deserts: star dunes, the vaguely pyramid-shaped sand formations up to about 1,000 feet (300 meters) tall with arms stretching out from a central peak to give them a star-like appearance when viewed from above.
Scientists on Monday unveiled the first in-depth study of a star dune, revealing the internal structure of these geological features and showing how long it took for one of them to form - more quickly than expected but still a process unfolding over many centuries.
The study focused upon a star dune in eastern Morocco called Lala Lallia, meaning "highest sacred point" in the local Berber language, situated within the Sahara Desert in a small sand sea called Erg Chebbi about 3 miles (5 km) from the town of Merzouga, close to the border with Algeria.
Lala Lallia rises about 330 feet (100 meters) above the surrounding dunes and is approximately 2,300 feet (700 meters) wide, containing about 5-1/2 million metric tons of sand.
According to Reuters, he researchers used ground-penetrating radar to peer inside the dune and employed luminescence dating to determine how long Lala Lallia has taken to form, a method based on the amount of energy trapped inside the grains of sand. The answer: about 900 years, accumulating roughly 6,400 metric tons annually as wind relentlessly blows sand through the desert.
Star dunes make up just under 10% of the dunes in Earth's deserts and are the tallest ones, surpassing other types such as crescent-shaped barchan dunes and straight and lengthy linear dunes. They also have been spotted on Mars and on Saturn's large moon Titan.
"I first encountered star dunes in Namibia 20 years ago, and was instantly amazed at the size of them. I have a vivid memory of the long climb to the top, struggling up very loose sand in the heat of the day," said geographer Geoff Duller of Aberystwyth University in Wales, co-author of the study published in the journal Scientific Reports.
"I find desert dunes very beautiful," Duller added. "The sight of the sinuous curves, and the way that the light and shadow changes with the sun mean that they always look different, whether that is in the cool of the morning, the midday sun or near sunset. The different colors of sand in different deserts are also very striking, with yellow, white, red and even black dunes in different parts of the world."
The ground-penetrating radar revealed the layers within the Lala Lallia dune, showing how it was constructed over time through accumulating sand and how parts of its internal structure resembled other types of dunes.
"Star dunes are formed in areas with complex wind regimes, which means winds blowing from different directions, and net sand accumulation, points within the desert where big piles of sand can be blown around to form giant dunes," said Birkbeck University of London sedimentologist and study co-author Charlie Bristow.
The researchers also determined that Lala Lallia is moving westerly at a speed of about 1.6 feet (0.5 meters) annually.
While many star dunes are known today, only a single ancient one has been found preserved as sandstone in the geological record, dating to about 250 million years ago, in Scotland. By revealing their internal structure, the researchers said their findings provide a guide for geologists to identify more sandstone remnants of ancient star dunes.
Earth's largest star dunes are found in the Badain Jaran desert in western China. Star dunes also are found in places including the Namib Sand Sea in Namibia, large sand seas in Algeria such as the Grand Erg Oriental and Grand Erg Occidental, and Rub' al Khali in Saudi Arabia. In North America, Great Sand Dunes National Park in Colorado contains a series of them.
"They form extraordinary and awe-inspiring landscapes," Bristow said. "From the ground they can be intimidating, mobile mountains of sand."

Most Viewed

 
Varieties

Horse Therapy Program in Namibia Brings Joy to Children with Learning Disabilities

Merci who participates in the "Enabling Through the Horse," therapy program outside Windhoek, Namibia, pets a horse on Feb. 18, 2025. (AP)
Merci who participates in the "Enabling Through the Horse," therapy program outside Windhoek, Namibia, pets a horse on Feb. 18, 2025. (AP)
TT
20
TT

Horse Therapy Program in Namibia Brings Joy to Children with Learning Disabilities

Merci who participates in the "Enabling Through the Horse," therapy program outside Windhoek, Namibia, pets a horse on Feb. 18, 2025. (AP)
Merci who participates in the "Enabling Through the Horse," therapy program outside Windhoek, Namibia, pets a horse on Feb. 18, 2025. (AP)

Susan de Meyer's horses have different effects on different children. Hyperactive kids learn to be a little quieter around them while nonverbal children are moved to communicate and to bond with them.

De Meyer runs a program in the southern African country of Namibia that harnesses the power but also the gentleness of horses to help children with learning disabilities and conditions like ADHD and autism.

Each weekday morning, de Meyer's dusty paddock just outside the capital, Windhoek, is enlivened by a group of eight to 10 children from one of the special schools she helps. The children ride the horses, groom them, stroke them and often, de Meyer says, talk to them.

De Meyer grew up on a farm surrounded by horses and they've always been part of her life. She said they have a quality that is invaluable: They don't judge the children, no matter how different they are.

"The horse is the hero in this whole situation because these kids don’t want to be around a lot of people," de Meyer said.

De Meyer's program, "Enabling Through the Horse," is supported by the Namibian Equestrian Federation and won an award last year from the International Equestrian Federation because it "underlines the wonderful characteristics of the horse in exuding sensitivity and intuition."

Horse therapy has been promoted by autism groups and those that work with children with learning disabilities as having a positive impact. And animal therapy in general has been found to be useful in many instances, like dogs that help military veterans with post-traumatic stress disorder and therapy cats that are taken to hospitals and nursing homes.

Some survivors of the devastating 2023 Hawaii wildfires found relief in horse therapy while grieving loved ones they had lost.

De Meyer jokes she has "two-and-a-half horses." These include two Arabians — a white mare named Faranah and a brown gelding, Lansha — while the "half" is a miniature horse called Bonzi, who is about head-high for a 5-year-old.

The Arabians are often the most useful for the children's therapy because of their size, de Meyer said.

"It gives them self-esteem. When they stroke the horse, the therapy starts because this is a very big animal compared to their height, and they are not scared to stroke the horse ... and then to ride it and tell the horse what they want," she said.

De Meyer works with children with a range of conditions or disabilities, including autism, attention-deficit/hyperactivity disorder, Down syndrome, those who are nonverbal or touch sensitive, and some who were born with fetal alcohol syndrome and have developmental problems.

She has received interest from other countries in Africa and Asia to start similar programs there.

"The changes that I’ve seen with the learners are significant," said Chriszell Louw, a teacher at Dagbreek School, which says it is one of just two government schools in Namibia for children with intellectual disabilities. "We have a learner that likes to talk a lot. When we come here, she knows she has to keep quiet. She sits in her place."

"Some of them you see they are more open, they are happy. Some of them were very scared when they started with the horse riding but now they are very excited. When they hear we’re going to the horses they are very excited and just want to go by themselves," Louw said.

De Meyer said her program helps with fine-motor skills, gross-motor skills, muscle strengthening, coordination, balance and posture, all important for kids who struggle to sit at a desk at school and learn.

One simple exercise de Meyer has children do when they ride is to let go of the reins and stretch their arms out straight and to the sides, using only their torso and lower body to balance as a groom leads the horse around the paddock.

Some of the kids break out in smiles when they let go and look like they're soaring.

"We make the world different for these kids," de Meyer said.