资源环境科技发展态势分析平台

Eruptions of Kilauea Volcano, Hawai'i, USA, can be more powerful than previously recognized. The Kulanaokuaiki-3 (K-3) eruption, ca. 900 CE, consisted of two episodes that dispersed lithic wall-rock clasts (Episode 1) and dominantly scoria (Episode 2; VEI-3) across >65 km(2) southeast of the summit Dense 12 cm blocks of Episode 1 fell 8-10 km from the summit vent, and 2-4 cm lithic lapilli reached the coastline, 17 km from the vent. The Episode 2 deposit is chemically zoned, indicating orderly eruption from a layered magma body analogous to the 1959 Kilauea Iki lava lake. Olivine-hosted melt inclusions suggest a magma body within 1 km of the surface. Some Episode 1 lithic clasts have magmatic rinds chemically similar to the early Episode 2 scoria, suggesting a genetic link, although each had a distinct eruption mechanism. Southeastward tephra dispersal counter to NE trade winds implies dispersal by jet-stream winds. The dispersal of lithic clasts in Episode 1 cannot be explained by ballistic trajectories or by transport in a buoyant plume. Calculations instead indicate that a jet from a vent with a minimum diameter of 50 m, a velocity of at least 300 m/s, and a duration of similar to 60 s could have lifted the lithic clasts into the jet stream. Isopach and isopleth maps for Episode 2 indicate a subplinian column height of 14-18 km and a duration of 2-3 h, assuming constant flux. The Episode 1 conduit probably intersected or otherwise lowered pressure within a compositionally zoned magma body, triggering eruption of the Episode 2 scoria.