Kusatsu-Shirane Volcano Research Articles

Organic geochemical features of an extremely acid crater lake(Yugama) of Kusatsu-Shirane Volcano in Japan.

Organic geochemical study on an extremely acid crater lake (Yugama, pH = 1.2) of an active Kusatsu-Shirane Volcano in Japan has been carried out to clarify the features and sources of organic components in relation to biological activity. Generally, n-alkanes ranging from n-C15 to n-C36 with a predominance of long-chain (n-C20–n-C36) n-alkanes maximizing at n-C27, n-C29 or n-C31 were detected in suspended solids (≥0.60 μm), sulfur aggregate and surface sediments of the lake, and soils in the surroundings of the lake, together with pristane, phytane, squalane, steranes and/or triterpanes. A series of n-alkanoic acids ranging from n-C8 to n-C32 with a predominance of even-carbon numbers were found in all the samples, along with cis- and trans-isomers of n-alkenoic acids [n-C16:1 (Δ7 and δ9) and n-C18:1 (Δ9 and Δ11)], iso- and anteiso-alkanoic acids (C14–C17), and cyclopropyl alkanoic acids (C17 and C19). No polyenoic alkenoic acids were, however, found in all the samples. Normal 3-hydroxy acids (n-C10–n-C18) mainly maximizing at n-C14 were detected, together with iso- and anteiso-3-hydroxy acids (C12–C18). The features of organic components in the lake waters and sediments indicate that they can be attributed to bacteria, such as Thiobacillus thiooxidans in addition to certain uncultured bacteria, with some influences of eroded, and/or wind-transported materials containing vascular plant debris from the surroundings of the lake. Low concentrations of fatty acids mainly reflect the paucity of photosynthetic producers and small living biomass in the lake. Relatively high trans/cis-C16:1 alkenoic acid ratios (0.24–0.52) may be caused by unfavorable habitat for microbial activity in the lake. The thermal maturation parameters of (20S/20R)-24-ethyl-5α(H), 14α(H), -17α(H)-cholestane ratios (0.49–0.77) and (22S/22R)-17α(H), 21β(H)-30-homohopane ratios (1.0–1.4) have not reached equilibrium values, but may have been significantly influenced by hydrothermal activity in the past in Lake Yugama and the surroundings of the lake.

Neutralization with Lime of Acidic Yukawa River Water from Kusatsu-Shirane Volcano

Neutralization with Lime of Acidic Yukawa River Water from Kusatsu-Shirane Volcano

B21-04 草津白根山における火山発散物の挙動

B21-04 草津白根山における火山発散物の挙動

草津白根山の噴出物中の粘土鉱物とその噴火形態

Phyllosilicates were present in the volcanic ashes from several 1982-1983 eruptions of Kusatsu-Shirane Volcano . Pyrophyllite, kaolin and smectite were present as major clay minerals. Hydrothermally altered rocks collected from the western flank showed that, the basement rocks of this volcano were altered to form silica minerals, alunite and various clay minerals such as pyrophyllite, kaolin and smectite. The presence of pyrophyllite in the volcanic ashes indicates that the explosions probably have taken at a depth corresponding to the basement rocks. On the other hand, samples of air-fall tephra from 1897 and 1925 eruptions contained little or no pyrophyllite suggesting that these explosions likely occurred in the volcanic rocks of Kusatsu-Shirane Volcano. Based on the distribution and amounts of clay minerals in the volcanic ejectas, the depth of explosions during repeated eruptions may be inferred.

Helium isotopes and CO 2 in volcanic gases of Japan

The isotope composition of He and its relationship to CO 2 have been investigated in gases sampled on 12 active volcanoes of Japan. The highest 3 He 4 He ratios reach the lower limit of the mid-ocean ridge basalt (MORB) range and have been recorded at Kusatsu-Shirane Volcano, which presented a phreatic activity during the sampling period, and at Satsuma-Iojima Volcano, where the highest temperature (786°C) was recorded. 3 He 4 He variations (3.1·10 −6–9.8·10 −6) suggest that, although 3He comes from the upper mantle, part of 4He is released from the crust in the volcano area. Time elapsed after volcanic events and distance from volcanics centers appear the major factors controlling these variations. CO 2 3 He molar ratios (4.5·10 9–29·10 9) are systematically higher than the MORB average of 2·10 9. The apparent excess of CO 2 (relative to 3He) cannot be entirely due to physical or chemical fractionation during the transfer of gases from the magmatic source to the surface. It is attributed to the effect of crustal outgassing or the contribution of a few percent of subducted sediments to the source of arc magmas. The last figure is in agreement with other geochemical tracers (Nd, Sr and pb isotopes, rare earth elements, 10Be, etc.). The estimated CO 2 flux at arcs is in the order of (1–5)·10 11 mol yr. −1 and represents <20% of the carbon flux at ridges. A mass balance of carbon at arcs shows that most sedimentary carbonates must be accreted rather than subducted. The flux of 3He at arc volcanoes represents <13% of the total volcanic 3He flux.

草津白根火山の噴火史

The eruptive history of the Kusatsu Shirane volcano is well described by means of 14 beds of key tephra and intercalating loess soil. Three eruptive stages are recognized. During early or middle Pleistocene the Matsuozawa volcano was formed; this is the first stage. The second stage was initiated by effusion of the Horaguchi lava, which was followed by eruptions of the Oshi pyroclastic flow, older lava flows, 3P pumice fall, and Yazawahara pyroclastic flow. Brown loess soil about 10m thick covering these deposits indicates that a dormant period of more than 100, 000 years followed this stage. The summit area upheaved about 400m or more against the foot of the volcano during this period, as is suggested by the extraordinarily steep (6.1°-3.0°) surface of the Oshi ignimbrite plateau. The third stage, which started about 14, 000 years ago, is the formation of three pyroclastic cones on the summit and contemporaneous effusion of the younger lava flows, e. g. the Kagusa lava of 7, 000 years ago and the Sessyo lava of 3, 000 years ago. In historic times, phreatic explosions have frequently occurred on the summit crater, Yugama. This means that the present belongs to the third stage. It is unlikely that eruptions of the third stage are caused by cooling of the magma chamber which was active in the second stage. The activity of the third stage seems to denote arrival of a new magma chamber at shallow depth.

60A. Clay Minerals in Volcanic Ejectas of Kusatsu-Shirane Volcano and Situations of Eruption.(Abstracts of Papers Presented at the Spring Meeting of the Society)

60A. Clay Minerals in Volcanic Ejectas of Kusatsu-Shirane Volcano and Situations of Eruption.(Abstracts of Papers Presented at the Spring Meeting of the Society)

40B. Seismological observation at Kusatsu-Shirane volcano.(Abstracts of Papers Presented at the Fall Meeting of the Society)

40B. Seismological observation at Kusatsu-Shirane volcano.(Abstracts of Papers Presented at the Fall Meeting of the Society)

Age of the Kumakura Pumice Fall Deposit Erupted from Kusatsu-Shirane Volcano, Central Japan

Age of the Kumakura Pumice Fall Deposit Erupted from Kusatsu-Shirane Volcano, Central Japan

12P. History of the Kusatsu Shirane volcano revealed by tephra and volcanic loess soil.(Abstracts of Papers Presented at the Spring Meeting of the Society)

12P. History of the Kusatsu Shirane volcano revealed by tephra and volcanic loess soil.(Abstracts of Papers Presented at the Spring Meeting of the Society)

Correlation of Volcanic Activity with Sulfur Oxyanion Speciation in a Crater Lake

The Yugama crater lake at Kusatsu-Shirane volcano, Japan, contains nearly 2200 tons (2800 parts per million) of polythionate ions (Sn O(6)(2-), where n = 4 to 9). Analytical data on lake water sampled before and during eruptions in 1982 showed that the concentrations of polythionates decreased and sulfate increased in response to the preeruption activities of the subaqueous fumaroles. These changes were observed 2 months before the first phreatic explosion on 26 October 1982. The monitoring of polythionates and sulfate in crater lake water is a promising means of anticipating potential volcanic eruption hazards.

60A. Recent activity of Kusatsu-shirane volcano from the chemical view point and monitoring system of the crater lake Yugama(Abstracts of Papers Presented at the Spring Meeting of the Society)

60A. Recent activity of Kusatsu-shirane volcano from the chemical view point and monitoring system of the crater lake Yugama(Abstracts of Papers Presented at the Spring Meeting of the Society)

59. Extra geophysical observation at Kusatsu-Shirane Volcano from 20 July to 6 August 1983(Abstracts of Papers Presented at the Spring Meeting of the Society)

59. Extra geophysical observation at Kusatsu-Shirane Volcano from 20 July to 6 August 1983(Abstracts of Papers Presented at the Spring Meeting of the Society)

60. The 1982-1983 eruption of the Kusatsu-shirane Volcano (II)(Abstracts of Papers Presented at the Spring Meeting of the Society)

60. The 1982-1983 eruption of the Kusatsu-shirane Volcano (II)(Abstracts of Papers Presented at the Spring Meeting of the Society)

41. Surface temperature measurements at Kusatsu-Shirane Volcano on 29-30, October 1982(Abstracts of Papers Presented at the Spring Meeting of the Society)

41. Surface temperature measurements at Kusatsu-Shirane Volcano on 29-30, October 1982(Abstracts of Papers Presented at the Spring Meeting of the Society)

Photo 1. Eruption of Kusatsu-shirane volcano on December 29, 1982

Photo 1. Eruption of Kusatsu-shirane volcano on December 29, 1982

Photo 2. Eruption of Kusatsu-shirane volcano on October 26, 1982.

Photo 2. Eruption of Kusatsu-shirane volcano on October 26, 1982.

40. On the eruptions of Kusatsu-Shirane Volcano on October 26, 1982 and December 29, 1982(Abstracts of Papers Presented at the Spring Meeting of the Society)

40. On the eruptions of Kusatsu-Shirane Volcano on October 26, 1982 and December 29, 1982(Abstracts of Papers Presented at the Spring Meeting of the Society)

Phreatic Eruption of Kusatsu-shirane Volcano in 1982

Phreatic Eruption of Kusatsu-shirane Volcano in 1982

Chemical and isotopic compositions of acid hot spring waters around Kusatsu-Shirane volcano

Chemical and isotopic compositions of acid hot spring waters around Kusatsu-Shirane volcano