The iconic 'star dunes' found in deserts like the Sahara are captivating structures that have intrigued scientists for decades. These massive sand dunes, characterized by their distinctive star-like shape, can also be found on Mars and Titan, Saturn's largest moon. Recently, researchers have made a significant breakthrough in understanding these enigmatic formations by pinpointing the age of one of Earth's oldest star dunes. Named the Lala Lallia star dune and located in southeastern Morocco, this geological wonder is estimated to have formed approximately 13,000 years ago, shedding light on the long-standing mystery surrounding the geological record of star dunes.
Star dunes, towering structures that dominate sandy landscapes across Africa, Arabia, China, and North America, are believed to be the tallest dunes on Earth, with some reaching staggering heights of up to 984 feet. Despite their prevalence in modern deserts, star dunes have been conspicuously absent from Earth's geological record, puzzling scientists for years. Only one ancient star dune, dating back approximately 250 million years, has been discovered preserved in sandstone in present-day Scotland. However, recent advancements in technology, such as ground-penetrating radar, have enabled scientists to delve into the secrets of star dunes like never before.
The Lala Lallia star dune, nestled in the Erg Chebbi area of the Sahara Desert, has provided researchers with invaluable insights into the formation and evolution of these natural wonders. Through meticulous analysis of its internal structure using ground-penetrating radar, scientists have uncovered the intricate history of this towering sand pyramid. The dune, which stands at an impressive height of 238 feet and spans 2,296 feet in width, has experienced rapid growth over the past millennium, gradually shifting westward. Intriguingly, the star dune's formation coincides with the Younger Dryas event, a period of abrupt global cooling around 12,900 to 11,600 years ago.
Furthermore, luminescence dating techniques have revealed fascinating details about the age and growth rate of the Lala Lallia star dune. By analyzing the energy stored in quartz grains within the sand, researchers determined that it took approximately 900 years for the dune to form, accumulating around 6,400 metric tons of sand annually. The findings not only offer unprecedented insights into the dynamics of star dune formation but also provide valuable clues about Earth's climatological history.
Moreover, the study underscores the potential of employing advanced techniques like ground-penetrating radar and luminescence dating to unravel the mysteries of other sand dunes worldwide. As study co-author Charlie Bristow of University College London explains, understanding the formation mechanisms of these immense dunes can enhance our understanding of Earth's geological history and aid in identifying similar desert features in the rock record.