REPORT

Volcanic gas fatality at

ADATARA VOLCANO
last updated on 30 th Sep,1997
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The purpose of this page is to present a report on volcanic gas disaster of ADATARA VOLCANO occured on 15th Sep ,1997.

This page is maintained by Tatsuro CHIBA and Takeshi KAMOSHIDA.


Volcanic gas fatality at Adatara Volcano

Four hikers lost their lives due to volcanic gas in a summit (Numano-daira) crater on 15 September. A party of 14 enjoyed hiking near the summit in foggy and calm condition. They lost a mountain trail near the western mouth of the crater, the lowest level on crater rim. They then wandered into the crater, looking for the trail. Three people fell in the southwestern part of the crater floor, and a person who tried to help them did too. The rest of the party harriedly climbed up the higher levels. Along the trail, notice boards for volcanic gas danger zone stood for hikers.

According to Jun-ichi Hirabayashi, Kusatsu-Shirane Volcano Observatory, Tokyo Institute of Technology, fumarolic gas from the southwestern part within the crater, contained 0.5 % of SO2, 60-65 % H2S and 33-37 % CO2 as dry basis, and gas collected this July from a mud pond on the crater floor contained H2S of 41% and CO2 of 56%. He pointed out inhalation of H2S as the most possible reason of this fatality. Volcanic gas probably accumulated in the low level due to no wind condition.

JMA issued "Volcanic Observation Report on Adatara Volcano, No.1" in the afternoon, September 15, in which this volcano has raised its activity these years, such that mud was spouting from two ponds on the crater floor and fumarolic activity has heightened in the southwestern part. They gave the public warning of danger to approach the crater area. JMA observed no volcanic tremors at this volcano these months, except for 5 volcanic earthquakes in August.

from http://hakone.eri.u-tokyo.ac.jp/vrc/erup/adatara.html

Field photos on Sep 23, 1997
Numanotaira crater central part of Adatara volcano was surveyed by CHIBA, KAMOSHIDA and FUJINAWA on Sep. 23, 1997. The weather condition was not good, but we could reach the site of gas accident, wearing gas mask and sensor for H2S.

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photo-1

The attention board for volcanic gas that was made just after the accident. (T.C.)

photo-2

Mud fountain has been still acitive. This mud volcano has been observed since the 1997-spring. (T.C.)

photo-3

Another new mud fountain.(T.C.)

photo-4

Hot water gushed out from some points, and yellowish silty deposits were found on the bottoms of small creeks. (T.C.)

photo-5

Volcanic gas-gushing zone in the southern part of Numanotaira crater. Yellowish materials are sulfer sublimate. (T.K.)

photo-6

Elevated pressure of gas may have destroyed a breccia in alluvium deposits. (T.C.)

photo-7

The site of gas accident is the head of small V-shaped valley. The outlet of this valley locates just in the H2S gushing field. (T.C.)

photo-8

Stereo-view of the accident site. (T.C.)

photo-9

Turning point of the valley, where lake tarrace deposits acted as barrier against H2S gas. (T.C.)

photo-10

White flowers truned pink on the rock surface. (T.C.)

photo-11

Gas sensor indicated over 100 ppm H2S. Even through gas mask, the gas smells like natural oil gas. (T.C.)

photo-12

The site of accident is on the bottom of valley. The detected value of H2S is higher than 200 ppm. (T.K.)

photo-13

The rock surface around here is black in color. (T.C.)

photo-14

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photo-15


The hiker group turned right at here rather than went straight because of heavy fog.

The surface of Numanotaira crater easily becomes wet, then harder for hikers to walk; the trail could not be found by them.(T.C.)

photo-16

Estimated route which the hiker group took (1). The background photo was taken in 1974 by Geographical Institute of Japan. (T.K.)

photo-17

Estimated route which the hiker group took (2). The background photo was taken on Sep. 12, 1996 by T.K.

photo-18

Whole scenery of Numanotaira crater taken in May 1997 by S.

photos and edition by T.C., T.K, and S. (T. Chiba, T.Kamoshida, and Suzuki)

LINKS

Volcanic gas fatality at Adatara.. by VRC-(in English)

http://hakone.eri.u-tokyo.ac.jp/vrc/erup/adatara.html

The condition at 26th May 1997 by GSJ-(in Japanese)

http://www.aist.go.jp/GSJ/dEG/sVOLC/Adatara.html

The condition of 2nd May 1997 by TC -(in Japanese)

http://www.geo.chs.nihon-u.ac.jp/tchiba/kamo/adatara9705.html

The condition of 1st Sep 1996 by TC-(in English)

http://www.geo.chs.nihon-u.ac.jp/tchiba/adatara.html

Tatsuro CHIBA's volcanic home page