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| Extensive Pyroclastic sheetflows, Northern Chile -- Two massive pyroclastic pyroclastic sheetflows (ignimbrites) are seen here in the Rio Loa canyon of northern Chile. Their volumes are excess of 1,000 cubic kilometers each and they were extruded for distances over 100 km from their source calderas in the Central Andes. The lowermost unit is 8.1 million years old. Courtesy of Peter Francis. |