Pyroclastic edifices record vigorous lava fountains during the emplacement of a flood basalt flow field, Roza Member, Columbia River Basalt Province, USA

The 1300 km3 tholeiitic lava flow field of the 14.98 Ma Roza Member of the Columbia River Basalt Province has the best-preserved vent system of any known continental flood basalt. Detailed geological mapping and logging of the exposed pyroclastic rocks along the >180-km-long vent system enable the reconstruction of pyroclastic edifices (partial cones) built around vents. The pyroclastic cones differ from those constructed during typical basaltic effusive eruptions and are characterized by low to moderate slope angles (1 km) fountains enhanced by fallout from the lower parts of convective plumes that rose above the fountains.