A strange type of yellow and exotic glass found in some of the desert regions of the world has finally had its mysterious origins identified – nearly 30 million years after its formation on Earth.
The glass of the Libyan desert is a type of natural glass that is found in the eastern reaches of the Sahara Desert, in eastern Libya and in western Egypt. Its rare yellow color has seen it used in a decorative way dating back to the age of Tutankhamun, but the desert glass was much longer than that.
The formation of this strange glass was dated some 29 million years ago, but the forces that brought the material to exist on Earth have never been clearly defined, although two major hypotheses have dominated the conversation.
"The question of whether the glass formed during the impact of a meteorite or during an air explosion was debated when asteroids called near-Earth objects explode and are depositing energy into the earth 's atmosphere, "says geologist and planetary scientist Aaron Cavosie Curtin University in Australia.
According to Cavosie, previous models suggested that glass from the Libyan desert could have formed during explosive events, much like the spectacular Chelyabinsk explosion that occurred in Russia in 2013.
But new research gives us the first "unequivocal justification" that this might not be the case after all.
In a new study, Cavosie examined small grains of zircon contained in glass samples from the Libyan desert. The analysis has highlighted traces of another mineral called reidite, which forms under high pressure, but only during meteorite impacts (as found only in craters). impact), and not by air explosions.
"Meteorite impacts and aerial explosions can cause melting, however, only meteorite impacts create shock waves that form minerals under high pressure," said Cavosie.
"So, finding evidence from a former reidite confirms that it was created as a result of a meteorite impact."
According to the researchers, the identification of the reidites does not help us just to close the book on the creation of this ancient glass of the desert.
It also allows us to clarify, with reference to geological records, the frequency at which shock wave-producing destructions producing shockwaves occur on Earth – since there are no glass deposits associated with a flash of air that has formed in the last 5 million years.
Because we now know that only major and much rarer meteorite impact phenomena can produce Libyan desert glass, it is hoped that it will be another incredible age before this yellow material has the chance to be of merged again on Earth, as attractive as it is.
"Meteorite impacts are catastrophic events, but they are not common," said Cavosie.
"Air explosions occur more frequently, but we now know that we should not expect a glass formation event in the Libyan desert in the near future, which is comforting".
The results are reported in Geology.