Giant, moving Moroccan star dune mystery solved

Researchers, including experts from Aberystwyth University in Wales, have determined the age and formation details of a star dune in a remote area of Morocco.

These intriguing structures, resembling pyramids from the ground and stars from the air, are not only found on Earth but also on Mars and Titan, Saturn’s largest moon. The team studied a 100-meter high and 700-meter wide dune in the Erg Chebbi sand sea in Morocco, known as Lala Lallia, discovering that its base was 13,000 years old. However, the upper part of the dune, forming the distinctive star shape, is relatively young, dating back only about 1,000 years.

The dune’s formation was influenced by changing climate conditions, stabilizing and shifting over millennia due to wind patterns. Luminescence dating techniques, developed at Aberystwyth, were crucial in determining the age of the dune by analyzing when the sand grains were last exposed to sunlight.

The findings shed light on the dynamic nature of these natural wonders and their significance in planning infrastructure in areas prone to their slow movement. The research was published in the journal Scientific Reports.

Professor Geoff Duller of Aberystwyth University’s Department of Geography and Earth Sciences, leading the research, described star dunes as extraordinary natural wonders. From the ground, they resemble pyramids, but when viewed from above, they exhibit a peak with arms radiating in multiple directions, creating a star-like appearance.

The study focused on Lala Lallia, a star dune in the Erg Chebbi sand sea in Morocco, an area known for its unique dune formations. Researchers were surprised to find that while the dune’s base dated back 13,000 years, the upper part, responsible for its star shape, formed only within the last 1,000 years. The base built up until approximately 9,000 years ago, stabilizing during a wetter climate with traces of old plant roots suggesting vegetation stabilization. For around 8,000 years, the dune remained in this state, until changing climate conditions triggered the formation of the star dune.

Wind patterns played a crucial role in shaping the dune, with opposing winds from the south-west and north-east causing sand accumulation. Additionally, a steady third wind from the east gradually shifted the dune westward at a rate of approximately 50cm per year. This movement has practical implications for infrastructure planning, as the shifting dunes pose challenges for construction projects like roads and pipelines.

The luminescence dating techniques developed at Aberystwyth involved analyzing the last time sand grains were exposed to sunlight. This method relies on the quartz grains’ ability to store energy from natural radioactivity, releasing it as light when brought back to the laboratory. The brightness of the light emitted helps determine the age of the sand grains.

The study showcases the interdisciplinary nature of research, combining expertise in geography, earth sciences, and luminescence dating technology to unravel the mysteries of these captivating natural formations. As scientists continue to explore the age and dynamics of various landforms on Earth and beyond, their findings contribute to a deeper understanding of geological processes and the history of our planet.

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