Star dunes
- March 7, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
Star dunes
Subject: Geography
Section: Geomorphology
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
What are star dunes?
- Star dunes – or pyramid dunes – are named after their distinctive shapes and reach hundreds of metres in height.
- Star dunes make up just under 10% of the dunes in Earth’s deserts. These are the tallest ones, surpassing other types such as crescent-shaped barchan dunes and straight and lengthy linear dunes.
- These are formed in areas with complex wind regimes, where winds blowing from different directions and net sand accumulation, points within the desert where big piles of sand can be blown around to form giant dunes.
Geographical distribution:
- They are found in Africa, Asia and North America and also have been spotted on Mars and on Saturn’s large moon Titan.
- Earth’s largest star dunes are found in the Badain Jaran desert in western China.
- Namib Sand Sea in Namibia, large sand seas in Algeria such as the Grand Erg Oriental and Grand Erg Occidental, and Rub’ al Khali in Saudi Arabia.
- In North America, Great Sand Dunes National Park in Colorado contains a series of them.
Recent study about Star dunes
- The research team from the UK have estimated the age of star dune of Lala Lallia in Morocco, for the first time.
- The scientists used a technique called luminescence dating to work out the age of the star dune. The method calculates when the grains of sand were last exposed to daylight.
Types of dunes
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
Parabolic dunes – also called U-shaped, blowout, or hairpin dunes – tend to form where vegetation covers the sand. Winds may erode a section, pushing the sediment leeward. The vegetation will hold back the arms of the dune, so that the dune points in the leeward direction. The animation below gives a basic overview of how they form. They are most common in coastal deserts. Sometimes, parabolic dunes can come from transverse or barchan dunes, given that the dunes stay static enough for vegetation to grow on them.
Star
Star dunes are a rare, interesting dune structure, that pepper landscapes in sandy deserts. They form when alternating and multiple wind directions pile sand in a location, and forms a peak, with many arms extending from the center (Fun Facts…). Star dunes make up 8.5% of all the dunes on the planet, and they often form in large groups in a dune field (Star Dunes). Many of these fascinating dunes can be seen in the Sahara desert, especially in the Grand Erg Oriental, a “sand sea” of dunes.
Barchan
Barchan dunes are crescent or half-moon shaped, and are thus also called crescentic dunes. They form where conditions are ideal. They require a flat landscape, winds from only one direction, and limited sand. However, these exact conditions are rare, and so is this type of dune, although they are found in all types of deserts. Barchan dunes point against the wind. Their faces are steep, but their trailing sides are not. They will often join up with other barchans to form barchanoid ridges.
Longitudinal
Also called linear dunes, longitudinal dunes look like large, parallel needle-esque features on the landscape. They are straight, and long, unlike the typical dune that people imagine. This dune type forms when sand is not in excess, and when wind blows in one constant direction. Over an extended period of time the dunes will migrate in the direction the wind is blowing.