Scientists reveal secrets of Earth’s magnificent desert star dunes

THEY are among the wonders of our deserts: star dunes, the vaguely pyramid-shaped sand formations up to about 1000 feet (300 metres) 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 indepth 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 (5km) from the town of Merzouga, close to the border with Algeria.

Lala Lallia rises about 330 feet (100 metres) above the surrounding dunes and is approximately 2300 feet (700 metres) wide, containing about 5-1/2 million metric tonnes of sand.

The 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 6400 metric tonnes annually as wind relentlessly blows sand through the desert.

Star dunes make up just under 10 per cent of the dunes in Earth’s deserts and are the tallest ones, surpassing other types such as crescentshaped barchan dunes and straight and lengthy linear dunes. They also have been spotted on Mars and on Saturn’s large moon Titan.