The 2018 eruption on the lower East Rift Zone, Hawaii, involved the opening of 24 fissures before the eruption focussed on a single point source, fissure 8 (F8). This study characterises the preserved medial F8 tephra deposit using an isopach map, maximum clast size data, and total grain size distribution analysis, shedding light on the tephra transport and dispersal mechanisms beyond the F8 cone occurring during the fountaining. The medial sheet-like deposit covers approximately 0.22 km 2 , best fit by a Power-Law thinning rate. The TephraFits model estimated the corresponding volume of the continuous medial tephra blanket to be 2 × 10 4 m 3 , just 0.02

The unprecedented cost of the 2018 eruption in Hawai’i reflects an intersection of disparate physical and social phenomena: widely spaced, highly destructive eruptions, and atypically high population growth. These were linked and the former indirectly drove the latter with unavoidable consequences.

Interactions between fluid lava and the ocean can be explosive and thus hazardous to nearby communities. These eruptions can be difficult to study as at least half of the deposit is lost to the sea. During 2008, lava flows from episode 58 of Pu ʻ u ʻŌʻō entered the ocean near the town of Kalapana. The deposits are well-preserved, not covered by subsequent lava flows, and well-documented by photography; therefore, eruptive products can be tied to observed processes, making this event an ideal case study. We identified four different pyroclast categories on and around the preserved half-cone: Pele’s hair, Pele’s ‘locks’, fluidal spatter, and dense blocks. Photography reveals that steam generated from entrained sea water produced bubble-like bursts of juvenile material. This process is likely responsible for the first three pyroclast types, as all three require the material to still be fluid at time of formation. The blocks, however, are more ambiguous as to whether they represent fragmentation of lava tube walls or lava that drained back to the explosive vent. The fluidal spatter is crystal-poor and displays a distinct pattern between bubble texture and aspect ratio (AR; here, defined as the ratio of length to thickness) that implies a relationship between in-flight time and relative viscosity. Proximal spatter has very high ARs (max: 454), but the bubbles are small and spherical, suggesting that the spatter cooled very rapidly due to its thinness.