These structures are awe-inspiring and enigmatic, emerging from desert landscapes on Earth and also appearing on Mars and Saturn’s largest moon, Titan.
Academic researchers from various institutions, such as Aberystwyth University in Wales, have determined the age of a star-shaped sand dune located in a isolated region of Morocco. They have also revealed information about its creation and pattern of movement through the desert.
Professor Geoff Duller, from the department of geography and earth sciences at Aberystwyth, described these structures as “remarkable” and one of the world’s natural marvels. While they may appear as pyramids from a ground-level view, an aerial perspective reveals a peak with arms extending in three or four directions, resembling stars.
A group of University of London researchers journeyed to the southeastern region of Morocco to examine a dune in the Erg Chebbi desert called Lala Lallia. This dune stands at 100 meters tall and spans 700 meters in width, earning its name from the Berber term for “highest sacred point.”
They discovered that the very base of the dune was 13,000 years old but were surprised that the upper part of the structure had only been formed in the last 1,000 years or so. “It turned out to be surprisingly young,” said Duller.
The foundation of the dune gradually increased until approximately 9,000 years ago. After that, it reached a point of stability. Researchers believe that the environment may have been slightly more moist at that time compared to today. The presence of previous plant roots indicates that vegetation played a key role in stabilizing the dune. This stable state lasted for an approximate period of 8,000 years. However, changes in the climate caused the formation of a new star dune.
According to Duller, the dune’s shape is a result of two conflicting winds: one coming from the south-west and the other from the north-east, causing sand to accumulate. The dune is gradually moving westward at approximately 50cm per year due to a consistent eastward wind.
Duller emphasized the significance of considering displacement when constructing roads, pipelines, or other forms of infrastructure. He noted that these structures are subject to movement.
The age of the minerals in the sand was determined using luminescence dating techniques developed at Aberystwyth. These techniques revealed the last time they were exposed to sunlight.
According to Duller, our focus is not on the age of when the sand was created, as that was millions of years ago. Instead, we are interested in when it was placed. This is because the grains of quartz possess a characteristic similar to that of a small rechargeable battery.
“The substance has the ability to retain energy derived from natural radioactivity. Upon being transported to a laboratory, we can prompt the substance to emit this stored energy in the form of light. By measuring this light emission, we can determine the exact time the sand grain was last exposed to sunlight.”
An important rule is that the grains of sand must be collected without being in contact with light. To achieve this, they created holes in the dunes and inserted an outdated drainage pipe to collect the samples.
“That part isn’t terribly hi-tech,” said Duller. The work in the lab – which is much more hi-tech and sensitive – has to be carried out in the same sort of conditions as a photographic darkroom.
The same luminescence technique was used to date remnants of what is thought to be the world’s oldest known wooden structure, an arrangement of logs on the bank of a river bordering Zambia and Tanzania that predates the rise of modern humans.
The findings about the dunes were published in the journal Scientific Reports.
Source: theguardian.com
