Decade-long study of degassing at Kudriavy volcano, Iturup, Kurile Islands (1990–1999): Gas temperature and composition variations, and occurrence of 1999 phreatic eruption

Abstract

A high-temperature (up to 940• C) fumarolic activity at Kudriavy volcano had been studied during 1990-1999. The maximum gas temperatures of the fumaroles were measured in 1992 as 940• C, then gradually decreased with time and reached to 907• C in 1999. Gas composition of the high-temperature fumarole became enriched in H 2 O and depleted in other gas components, in particular in CO 2 . Hydrogen isotopic compositions of the high-temperature fumarolic gases were gradually depleted in deuterium. The gradual and continuous decrease in temperature and changes in gas composition observed during the last 10-year suggest that a magmatic melt have been degassing in a relatively steady-state manner from a single magma chamber. The detail investigations in 1998 and 1999 revealed short-term changes in gas composition characterized by sporadic increases in H 2 , CO 2 , and S total after intense precipitations. Small-scale eruptions occurred on October 7, 1999 at the summit. The ratios of major gas components (C/S, C/Cl, S/Cl, C/F, S/F, and Cl/F) significantly increased just prior to the eruption. The eruption at the Kudriavy volcano in 1999 was likely a phreatic eruption as a result of the intense precipitations after unusually long dry period. Meteoric water penetrated into the hot zone of volcano edifice and rapidly boiled causing the eruption.

Fumarolic-like activity on carbonaceous chondrite parent body

“…Kudryavy volcano consists of a small cone located in the northern end of Iturup island in the Kurile volcanic arc. The last large eruption occurred in 1883 and produced basaltic andesite flows, but small-scale phreatic eruption occurred more recently in 1999 ( 19 ). The Kudryavy basaltic andesite flows are composed of rare olivine, orthopyroxene (hyperstene), clinopyroxene (augite), plagioclase (labradorite to bytownite), and titanomagnetite ( 20 ) with porphyritic textures with fine-grained microlithic groundmass ( Figs.…”

Mid-crustal fluid related to the Matsushiro earthquake swarm (1965–1967) in northern Central Japan: Geochemical reproduction

“…A marked difference between them lies in the concentration of SO 4 . The moderate enrichment of SO 4 in the reproduced water may be a fingerprint of its volcanic origin since the magmatic fluid as a form of hightemperature volcanic gas is commonly concentrated in SO 2 together with HCl (Shinohara et al, 1993;Giggenbach, 1997;Korzhinsky et al, 2002).…”

Observing volcanoes with drones: studies of volcanic plume chemistry with ultralight sensor systems

“…Ideally, this ratio is monitored continuously to analyze changes in the gas composition of a volcanic system, which occur before, during and after a volcanic eruption to minimize the risk of an unforeseen eruption 2 – 5 . Indeed, a change in the CO 2 /SO 2 ratio has been observed at several volcanoes prior numerous eruptions, including Galeras 6 , Kilauea 7 , Kudriavy 8 , Villarica 9 , Aso 10 , and Etna 11 , 12 . An increase in the CO 2 /SO 2 ratio is often interpreted as evidence for the injection of deep CO 2 -rich magma or magmatic fluids into the degassing region 7 , 11 , 13 .…”