Pica glass, or Atacama desert glass, is a glass of debated origin, found along a broad 75.6 kilometer stretch of the Atacama Desert in northern Chile, including near the town of Pica, hence its name. Pica glass is notably lightweight, containing many folds, twists and flow lines, with pieces up to 50 centimeters across. The origin of Pica glass is debated. Some authors have suggested that it formed when a comet entered Earth's atmosphere and exploded over the Atacama Desert during the Late Pleistocene, sometime between 14,000 and 12,000 years ago. However, no unequivocal evidence supporting an extraterrestrial origin has been found to date, and the classification of the glass as cometary airburst glass remains speculative. An alternative formation hypothesis suggests that Pica glass formed as a result of surface vitrification after the burning of salt- and vegetation-rich soils due to natural fires in the Atacama Desert during different periods in the Late Pleistocene (supported by paleomagnetic data).
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