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Around 12,000 years ago, something scorched a vast swath of the Atacama Desert in Chile with heat so intense that it turned the sandy soil into widespread slabs of silicate glass. Now, a research team studying the distribution and composition of those glasses has come to a conclusion about what caused the inferno. In a study published in the journal Geology, researchers show that samples of the desert glass contain tiny fragments with minerals often found in rocks of extraterrestrial origin. Those minerals closely match the composition of material returned to Earth by NASA's Stardust mission, which sampled the particles...

A large proportion of the zircons found in Jurassic-era sandstones throughout a Texas-sized portion of the Colorado Plateau originated in the Appalachians, previous analyses have shown. Those erosion-resistant mineral grains were carried westward by an immense river, deposited on floodplains and then stirred back up innumerable times before ending up in massive dune fields that later solidified into western sandstones, says William R. Dickinson, a geologist at the University of Arizona in Tucson. In their attempt to trace the transcontinental river system, the researchers took a 20-kilogram hunk of Michigan sandstone from one of those quarries and then extracted and...