REPORT:
Evidence for water influx from a caldera lake during the explosive hydromagmatic eruption of 1790, Kilauea Volcano, Hawaii

Abstract

This study proposes that surface water, not groundwater, was the agent responsible for the explosiveness of the eruption. That is, a lake or pond may have existed in the caldera in 1790, and explosions took place when magma ascended into the lake from below. That assertion is based on two lines of evidence: (1) high vesicularity (avg. 73% of more than 3000 lapilli) and high vesicle-number density (10⁵-10⁷/cm³ melt) of pumice clasts suggest that some phases of the eruption involved vigorous, sustained magma ascent; and (2) numerical calculations suggest that, under most circumstances, hydrostatic pressure would not be sufficient to drive water into the eruptive conduit during vigorous magma ascent unless the water table were above the ground surface. These results are supported by historical data on the rate of infilling of the caldera floor during the early 1800s. When extrapolated back to 1790, they suggest that the caldera floor was below the water table.

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