[Rockhounds] Star dune: Scientists solve mystery behind Earth's largest desert sands

[Kreigh Tomaszewski]

Star dunes - or pyramid dunes - are named after their distinctive shapes
and reach hundreds of metres in height.

They are found in Africa, Asia and North America, as well as on Mars - but
experts had never before been able to put a date on when they were formed.

Now scientists have discovered that a dune called Lala Lallia in Morocco
formed 13,000 years ago.

Star dunes are created by opposing winds that change direction.
Understanding their age helps scientists understand those winds and unpick
the climate of that era, says Prof Geoff Duller at the University of
Aberystwyth, who published the research with Prof Charles Bristow at
Birkbeck University.

Lala Lallia (an indigenous Amazigh name meaning highest sacred point) is
located in the Erg Chebbi sand sea in south-east Morocco. It is 100m high
and 700m wide with radiating arms.

After its initial formation, it stopped growing for about 8,000 years and
then quickly expanded in the past several thousand years.

Normally deserts can be identified in Earth's geological history, but star
dunes were absent until now.

Prof Duller says this may be because they are so large that experts did not
realise they were looking at one distinct dune.

"These findings will probably surprise a lot of people as we can see how
quickly this enormous dune formed, and that it is moving across the desert
at about 50cm a year," he adds.

https://www.bbc.com/news/science-environment-68450147