What Happened on Kilauea Volcano About 2,000 Years Ago?

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9526405 Rhodes About 2000 years ago there was a profound perturbation in Kilauea's magmatic plumbing system. The effects lasted almost to the present Previous work has shown that, over most of this period, the lavas erupted at or near Kilauea's summit area have ranged in major, trace and isotopic compositions from lavas with the compositional characteristics of historical Kilauea magmas, through intermediate compositions, to lavas that closely resemble Mauna Loa magmas. There are two plausible explanations: either there were short-term changes in the proportions of source components in the Hawaiian plume that supply Kilauea, or magma from Mauna Loa invaded Kilauea' magmatic plumbing system, possibly in response to catastrophic caldera formation and eruption of the Uwekahuna Ash. This project is to complete this work and to test these two contrasting hypotheses. To test these observations, I will systematically sample sequential flows exposed continuously in the 100 m walls of Makaopuhi pit crater. This crater is 13 km down Kilauea's east rift zone from the summit caldera. Within the thick sequence of exposed flows are about 0.5-0.75 ka. Makaopuhi Crater is, therefore, an ideal location to test whether there are flows with anomalous Mauna Loa characteristics (1) that are older than the Uwekahuna Ash, and (2) that are far-removed from the summit caldera. Comprehensive major and trace element data will be obtained on these samples by XRF and INAA to determine their compositional affinities. In addition, Dr. J. P. Lockwood (USGS) and I will attempt to recover charcoal from beneath these flows and the ash layer to provide temporal control by 14C dating. With these questions resolved, we will be in a much better position to evaluate whether or not the Mauna Loa-like flows are a consequence of magmatic invasion from Mauna Loa, or whether there was a major perturbation in the proportions of source components supplying Kilauea from the Hawaiian plume during this period.