Gary sent in this link … https://www.bbc.co.uk/news/science-environment-68450147.amp … Star dunes. Scientists claim to have solved the mystery behind earth’s largest sand dunes. The subject of sand is dear to the heart of Gary as he has written a book, ‘Extraterrestrial Sands‘ [Gary Gilligan, Matador:2016].
The age of the earth’s largest and most complex types of sand dunes has been calculated. Star dunes are found in Africa, Asia and North America – and on Mars. A dune at Lala Lallia in Morocco formed around 13,000 years ago, they say, as a result of opposing winds that change direction. Lala Lallia is 100 m in height and 700 m wide – and has radiating arms. A bit like a spiral – or catherine wheel. Perhaps. After forming it stopped growing – for around 8000 years. Until around 3000BC. It has expanded since then. Mineral grains in the sand, according to Prof Geoff Duller of Aberystwyth University in Wales, are like ‘little rechargeable batteries’. They store energy within the crystals that comes from radioactivity in the natural environment, he adds. The longer the sand is buried under the ground the more radioactivity it is exposed to and the more energy it builds up. Around 3000BC the Sahara was in the process of growing and that is probably why that date is important. During the previous 8000 years the Sahara was green – which is why the star dune was in limbo. This takes us back to around 11,000 BC – roughly at the time of the Younger Dryas boundary. What was going on?
A day or so later Gary sent in another link – to https://scitechdaily.com/rethinking-earths-surface-geoscientists-discover-hidden-faults-of-the-pacific-plate/ … and this one comes from reseach at Toronto University. It seems the Pacific plate is not as rigid as previously thought but is instead torn by large undersea faults. This challenges tradional consensus views as far as Plate Tectonics is concerned, and suggest a more complex interaction between oceanic plates and the earth’s Mantle. On the other hand, Plate Tectonics might not be what it is all cracked up to be.
Some of the under the ocean faults are thousands of metres deep and hundreds of kilometres long. They are the result of enormous forces within the plate that are tugging it westward. They go on to blame the weight of the oceanic plate subducting along the western Pacific ring of fire. See https://doi.org/10.1029/2023GL105452 …