Lava‐seawater interactions at shallow‐water submarine lava flows

Abstract

Hydrothermal plumes associated with nearshore lava flows from Kilauea Volcano, Hawaii were studied on five occasions during 1989–1990 to address the current lack of data on direct lava‐seawater interactions. The following enrichments were found in the sea‐surface hydrothermal plumes above the active underwater lava flows: H2, 15,000x ambient seawater concentrations; Mn, 250x; and Si, 20x. Water temperatures reached 46°C. Lower concentrations and temperatures were observed in the plumes with increasing distance from shore, with H2, Si, and Mn concentrations linearly related to seawater temperature. Unlike deep sea spreading center hydrothermal plumes, no CH4 enrichment was observed. The elevated H2 is likely to be from water‐rock reactions, rather than from the release of magmatic gas. The plume mass/heat ratios presented here suggest that submarine flood basalts, although aerially large, should be relatively small immediate contributors to oceanic geochemical cycles compared to hydrothermal circulation through the crust.