Structures
The deposits of pyroclastic falls follow a well sorted and well bedded trend. They exhibit mantle bedding—the deposits directly overlie pre-existing topography and maintain a uniform thickness over relatively short distances. Sorting by size is more pronounced than pyroclastic surge or pyroclastic flows. Early settling of crystals and lithic fragments near an eruptive vent and of glassy fragments further away is a common trend witnessed during many eruptions. The St Vincent eruption in 1902 ejected a large eruption column which when settled near the vent contained 73% crystals, and ash deposited in Jamaica 1,600 km away consisted entirely of glass dust.
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—Friedrich Nietzsche (1844–1900)
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