Donald A. Swanson Sebastien Biass Sarah A. Fagents Tim R. Orr Bruce F. Houghton 2017 <p><span>We describe the discrete ballistic and wind-advected products of a small, but exceptionally well-characterized, explosive eruption of wall-rock-derived pyroclasts from Kīlauea volcano on 19 March 2008 and, for the first time, integrate the size distribution of the two subpopulations to reconstruct the true size distribution of a population of pyroclasts as it exited from the vent. Based on thinning and fining relationships, the wind-advected fraction had a mass of 6.1&nbsp;×&nbsp;10</span>⁵<span>&nbsp;kg and a thickness half distance of 110&nbsp;m, placing it at the bottom end of the magnitude and intensity spectra of pyroclastic falls. The ballistic population was mapped, in the field and by using structure-from-motion techniques, to a diameter of &gt;&nbsp;10–20&nbsp;cm over an area of ~0.1&nbsp;km</span>²<span>, with an estimated mass of 1&nbsp;×&nbsp;10</span>⁵<span>&nbsp;kg. Initial ejection velocities of 50–80&nbsp;m/s were estimated from inversion of isopleths. The total grain size distribution was estimated by using a mass partitioning of 98% of wind-advected material and 2% of ballistics, resulting in median and sorting values of −1.7</span><i>ϕ</i><span>&nbsp;and 3.1</span><i>ϕ</i><span>. It is markedly broader than those calculated for the products of magmatic explosive eruptions, because the grain size of 19 March 2008 clast population is unrelated to a volcanic fragmentation event and instead was “inherited” from a population of talus clasts that temporary blocked the vent prior to the eruption. Despite a conspicuous near-field presence, the ballistic subpopulation has only a minor influence on the grain size distribution because of its rapid thinning and fining away from source.</span></p> application/pdf 10.1002/2017JB014040 en American Geophysical Union Partitioning of pyroclasts between ballistic transport and a convective plume: Kīlauea volcano, 19 March 2008 article