Following on from yesterday. At https://phys.org/news/2021-11-vast-patches-glassy-chilean-ancient.html … deposits of dark silicate dust are strewn across a 75 km long corridor in the Atacame desert of northern Chile, between the Andes on the east, and the coastal range on the west. New research says they were likely formed by the heat of a come [or comet fragment] exploding close to the surface. It has been provisionally dated to 12,000 years ago. The heat was so intense it turned the sandy soil into slabs of silicate glass.
The findings are published in the journal Geology. Samples of the glass contain tiny fragments with minerals closely matching the composition of material returned to Earth by NASAs Stardust mission – which sampled particles from Comet Wild 2. What they are suggesting is that the comet, or meteor, exploded in the air, the shock wave and blast of which created the silicate glass. The particles fell downwards from the shattered cosmic object and wound up in the same formation. The researchers say this is clear evidence of glasses formed on Earth's surface and created by thermal reaction and winds from a fireball [blast phenomena] from an explosion in the lower atmosphere. Peter Schultz, a professor emeritus at Brown's University [dept of Earth, Environmental and Planetary Science] said, 'to have such a dramatic effect on such a large area, this was a truly massive explosion. Lots of us have seen bolide fireballs streaking across the sky, but those are tiny blips compared to this.'
In the Late Pleistocene the desert did not exist. There were trees and grassy wetland zones created by rivers coming out of the Andes mountians. Schultz adds, 'I think this site provides a template to help refine our impact models and will help in identifying similar sites elsewhere.' See https://doi.org/10.1130/G49426.1