Birkbeck scientist solves age of one of the Earth's largest and most complex types of sand dune for the first time
Star dunes are a natural wonder found in Africa, Asia and North America, as well as on Mars and on Titan, Saturn’s largest moon - but previously experts had never been able to put a date on when they were formed.
An in-depth study of a star dune has been conducted by scientists at Birkbeck, University of London and the University of Aberystwyth, revealing the internal structure and age of a star dune for the very first time.
The research team focused on a star dune called Lala Lallia in eastern Morocco, situated within the Sahara Desert. It is 100m high and 700m wide with radiating arms, and the researchers discovered that it was formed about 900 years ago.
Star dunes - or pyramid dunes - are named after their distinctive shapes and are the tallest dunes on Earth, reaching hundreds of metres in height. They are created by opposing winds that change direction, and make up just under 10% of the dunes in Earth’s deserts.
Charles Bristow, Professor of Sedimentology at Birkbeck, alongside Professor Geoff Duller at the University of Aberystwyth, used a technique called luminescence dating to work out the age of the star dune, which calculates when the grains of sand were last exposed to daylight.
The researchers also used ground-penetrating radar which revealed the layers within the Lala Lallia dune, showing how it was constructed over time through accumulating sand and how parts of its internal structure resembled other types of dunes. BSc Geology Birkbeck students helped with the radar survey on their field class in Morocco.
Charles said: “Star dunes are the tallest dunes on Earth, but we know very little about them. This is partly due to their size and steep slopes which makes it hard work climbing, and partly because of their remote desert locations.
“Our research is the first in-depth study of a star dune, and it changes our understanding of star dunes, as they can be younger than previously thought and mobile. In addition to this, while many star dunes are known today, only a single ancient one has been found preserved as sandstone in the geological record, dating to about 250 million years ago, in Scotland. By revealing their internal structure, our findings provide a guide for geologists to identify more sandstone remnants of ancient star dunes.”