Dispersal of ash in the great Toba eruption, 75 ka
One of Earth's largest known eruptions, the Toba eruption of 75 ka, erupted a minimum of 2800 km3 of magma, of which at least 800 km3 was deposited as ash fall. This ash may be entirely of coignimbrite origin and dispersed widely because of high drag coefficients on the predominantly bubble-wall shards. Shards of this shape are broken from the walls of spherical vesicles, which formed in high abundance in isotropic strain shadows near phenocrysts in this crystal-rich magma.
Rose, William I. and Chesner, C. A., "Dispersal of ash in the great Toba eruption, 75 ka" (1987). Department of Geological and Mining Engineering and Sciences Publications. 124.