Componentry of pyroclastic fall deposits from 2008-2012 small explosive eruptions at Kilauea summit crater: insights into the dynamics of an open basaltic lava column

Eruptive activity began at Kilauea volcano's summit in March 2008 after 25 years of repose, when a small explosive event opened a 35-m-wide vent on the south wall of Halema`uma`u crater, initiating an eruptive period that extends to the time of writing. The activity has been characterized by: 1) a vigorous outgassing, 2) an unevenly intense spattering of the free surface at the top of the lava column (background activity), and 3) the occurrence of small explosive events consistently triggered by conduit-wall and/or rim collapses. A daily sampling of the pyroclasts ejected from the vent has been organized by the Hawaii Volcano Observatory since 2008. The componentry analyses of samples collected prior to and following different events from 2008 to 2012 allow us to distinguish consistent classes of juvenile particles according to their vesicularity, crystallinity and morphology. The abundances of these different classes vary from background- to explosion-samples, revealing consistent contrasting degassing and fragmentation processes before the disruption of the lava free surface by the rockfalls, and during and soon after the explosive events. These results, for samples collected in 2011-2012 combined with geophysical and visual datasets, give insights into the dynamics of the lava column and particularly into the behavior of the top of the column responding to outgassing and external disruption of the free surface-equilibrium state.