Journal Article10.1007/S00445-017-1105-0
Volcanic gas composition changes during the gradual decrease of the gigantic degassing activity of Miyakejima volcano, Japan, 2000-2015
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TL;DR: The composition of volcanic gases discharged from Miyakejima volcano has been monitored during intensive degassing activity that began after the eruption in 2000 and quickly decreased to 5kt/day by 2003.
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Abstract: The composition of volcanic gases discharged from Miyakejima volcano has been monitored during the intensive degassing activity that began after the eruption in 2000. During the 15 years from 2000 to 2015, Miyakejima volcano discharged 25.5 Mt of SO2, which required degassing of 3 km3 of basaltic magma. The SO2 emission rate peaked at 50 kt/day at the end of 2000 and quickly decreased to 5 kt/day by 2003. During the early degassing period, the volcanic gas composition was constant with the CO2/SO2 = 0.8 (mol ratio), H2O/SO2 = 35, HCl/SO2 = 0.08, and SO2/H2S = 15. The SO2 emission rate decreased gradually to 0.5 kt/day by 2012, and the gas composition also changed gradually to CO2/SO2 = 1.5, H2O/SO2 = 150, HCl/SO2 = 0.15, and SO2/H2S = 6. The compositional changes are not likely caused by changes in degassing pressure or volatile heterogeneity of a magma chamber but are likely attributed to an increase of hydrothermal scrubbing caused by large decrease of the volcanic gas emission rate, suggesting a supply of gases with constant composition during the 15 years. The intensive degassing was modeled based on degassing of a convecting magma conduit. The gradual SO2 emission rate that decrease without changes in volcanic gas composition is attributed to a reduction of diameter of the convecting magma conduit.
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TL;DR: Spectroscopic measurements performed during both quiescent degassing and explosions on Stromboli volcano are used to demonstrate that gas slugs originate from as deep as the volcano-crust interface (∼3 kilometers), where both structural discontinuities and differential bubble-rise speed can promote slug coalescence.
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Excessive degassing of Izu-Oshima volcano: magma convection in a conduit
TL;DR: In this article, a convective transport of magma through a conduit is proposed as the mechanism that causes degassing from a reservoir at several kilometers depth, which is quantitatively evaluated based on two fluid-dynamic models: Poiseuille flow in a concentric double-walled pipe, and ascent of non-degassed magma spheres through the conduit filled with degassed volatiles.
302
Spectroscopic evidence for a lava fountain driven by previously accumulated magmatic gas
TL;DR: Analysis of magmatic gas during a powerful lava fountain, measured with Fourier transform infrared spectroscopy on Mount Etna, Sicily, reveals a fountain gas having higher CO2/S and S/Cl ratios than other etnean emissions, and which cannot derive from syn-eruptive bulk degassing of Etna basalt.
272
Caldera collapse during the 2000 eruption of Miyakejima Volcano, Japan
TL;DR: A collapsed caldera, 1.6 km in diameter and 450 m in depth, was formed at the summit of Miyakejima Volcano during the 2000 eruption as mentioned in this paper.
251
Modelling the dynamics and thermodynamics of volcanic degassing
David Stevenson,Stephen Blake +1 more
TL;DR: In this paper, the authors investigated the convective overturn of dense degassed and less dense gas-rich magmas in a vertical conduit linking a shallow degassing zone with a deep magma chamber.