Context: Scientist unveiled the first in depth study of star dune, revealing the internal structure of these geological features and showing how long it took for one of them to form.
Sand Dunes
Sand dunes: deposition occurs due to obstruction to the winds caused by various factors. Depending upon their shape and alignment with respect to wind direction they are classified as:
Barchans: - crescent-shaped sand dune produced by the action of wind predominately from one direction.
- One of the most common types of dunes, it occurs in sandy deserts all over the world.
- Barchans are convex facing the wind, with the horns of the crescent pointing downwind and marking the lateral advancement of the sand.
- These dunes are markedly asymmetrical in cross section, with a gentle slope facing toward the wind and a much steeper slope, known as the slip face, facing away from the wind.
Parabolic dunes: - They are similar to crescentic dunes.
- Their shapes are roughly the same, but the slip face of a parabolic dune is on its inward side.
- Parabolic dunes are also called blowouts, because winds blow out the center of the dune, leaving just a rim on the outside.
Transverse dunes: - Barchan dunes can become aligned together along a plane perpendicular to the wind. If the line becomes somewhat straight, dune scientists refer to these forward marching ridges as transverse dunes.
- They progress forward as their leeward slip faces release sand one avalanche at a time.
Star Dunes
- Star dunes are massive sand dunes that owe their name to arms that spread from a central peak.
- These sand pyramids, which look like stars when viewed from above, are widespread in modern deserts including sand seas in Africa, Arabia, China, and North America.
- Star Dunes are formed in areas with complex wind regime which means wind are blowing from different direction and net sand accumulation, points within the desert where big piles of sand can be blown around to form giant dunes.
- It makes up just under 10% of the dunes in Earth’s deserts and are tallest, surpassing other type such as crescent shaped barchan dunes and straight and lengthy linear dunes.
Study Reveals
- The study focused upon a star dune in eastern Morocco called Lala Lallia, situated within the Sahara Desert.
- The researchers used ground penetrating radar and employed luminescence dating to determine how long Lala Lallia has taken to form, a method based on the energy trapped inside the grains of sand.
- It took about 900 years, accumulating roughly 6,400 metric tons annually as wind blows sand through the desert.