Factors influencing the height of Hawaiian lava fountains: implications for the use of fountain height as an indicator of magma gas content |
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| Authors: | E A Parfitt L Wilson C A Neal |
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| Institution: | (1) Department of Geological Sciences, Brown University, 02912 Providence, RI, USA;(2) Environmental Science Division, Lancaster University, LA1 4YQ Lancaster, UK;(3) Alaska Volcano Observatory, U.S. Geological Survey, 4200 University Drive, 99508 Anchorage, AK, USA;(4) Present address: Department of Earth Sciences, University of Leeds, LS2 9JT Leeds, U.K. |
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| Abstract: | The heights of lava fountains formed in Hawaiian-style eruptions are controlled by magma gas content, volume flux and the amounts of lava re-entrainment and gas bubble coalescence. Theoretical models of lava fountaining are used to analyse data on lava fountain height variations collected during the 1983–1986 Pu'u 'O'o vent of Kilauea volcano, Hawaii. The results show that the variable fountain heights can be largely explained by the impact of variations in volume flux and amount of lava re-entrainment on erupting magmas with a constant gas content of  0.32 wt.% H2O. However, the gas content of the magma apparently declined by 0.05 wt.% during the last 10 episodes of the eruption series and this decline is attributed to more extensive pre-eruption degassing due to a shallowing of the sub-vent feeder dike. It is concluded that variations in lava fountain height cannot be simply interpreted as variations in gas content, as has previously been suggested, but that fountain height can still be a useful guide to minimum gas contents. Where sufficient data are available on eruptive volume fluxes and extent of lava entrainment, greatly improved estimates can be made of magma gas content from lava fountain height. |
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| Keywords: | Lava fountains Magma gas content Volume flux Gas bubble coalescence Lava re-entrainment Pu'u 'O'o eruption |
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