Star Sand Dunes: Unveiling Earth’s Largest Mysteries

Sand dunes are common features of deserts, but not all of them are alike. Among the various types of dunes, star dunes are the most striking and mysterious. These are giant sand pyramids with arms that radiate from a central peak, giving them a star-like appearance when viewed from above. Star dunes are found in some of Earth’s largest modern deserts, such as the Sahara, the Gobi and the Mojave, but also on other planets and moons, such as Mars and Titan. They are believed to be the tallest dunes on Earth, with some reaching up to 300 meters in height. But how old are these dunes and how did they form?

The Age of Star Dunes

Until recently, scientists had no reliable way of dating star dunes and estimating their growth rate. Star dunes were almost absent from Earth’s geological record, which preserves the history of past deserts in layers of rock and sediment. Only one ancient star dune, dating back to about 250 million years ago, was found in present-day Scotland . This suggested that star dunes were either very rare or very difficult to recognize in the past.

However, a new study published in March 2024 in the journal Scientific Reports has solved this mystery by using a novel technique called luminescence dating . This method measures the amount of light emitted by grains of sand when they are exposed to light in a laboratory. The brightness of the light indicates how long the sand grains have been buried under ground, and thus how old they are.

Using this technique, the researchers dated one of Earth’s oldest star dunes, called Lala Lallia, which is located in the Erg Chebbi region of the Sahara desert in Morocco. Lala Lallia is an impressive star dune that measures 100 meters in height and 700 meters in width, with four radiating arms. The researchers found that the oldest parts of the dune are about 13,000 years old, while the youngest parts are only a few hundred years old . This means that Lala Lallia formed at the end of the last Ice Age, when the climate was changing rapidly and the winds were shifting direction.

The Formation of Star Dunes

Star dunes are formed by winds that blow from different directions throughout the year. These winds pile up sand around a central point, creating a pyramid shape with arms that point towards the wind directions. The more variable the wind direction, the more arms a star dune can have. Some star dunes have up to six arms .

The shape and size of star dunes also depend on the availability of sand and the stability of the surface. Star dunes tend to grow larger and taller where there is plenty of sand supply and where the ground is hard or rocky, preventing the sand from spreading out . Star dunes can also move across the desert at different speeds, depending on the wind strength and direction. For example, Lala Lallia is moving westward at a rate of about 50 centimeters per year .

The Importance of Star Dunes

Star dunes are not only fascinating natural wonders, but also important indicators of past and present environmental conditions. By studying their age and formation, scientists can learn more about the history of climate change, wind patterns and desertification on Earth and other planets . Star dunes can also provide valuable information about the biodiversity and ecology of desert ecosystems, as they host a variety of plants and animals that have adapted to their harsh environment .

Conclusion

Star sand dunes are unveiling some of Earth’s largest mysteries by revealing their secrets to scientists. These magnificent structures are among the oldest and most complex types of desert sand formations, but their age and formation are still poorly understood. By using new techniques such as luminescence dating, researchers can now estimate how old these dunes are and how they formed. This can help them understand more about the past and present climate, wind and desert conditions on Earth and other worlds.

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