Active Volcanoes In Japan Research Articles

A model for crustal deformations associated with the 1914 great eruption of Sakurajima volcano, Kagoshima, Japan

Sakurajima volcano, which is located on the southern rim of the Aira caldera, Kagoshima, is one of the most active volcanoes in Japan. The 1914 eruption of Sakurajima volcano was accompanied by an intensive fissure eruption and caused significant crustal deformations. The north side of the newly formed fissure craters, which are arranged in the WNW-ESE direction, moved toward the north by about 5 m, and the south side moved toward the south by 3 m. Furthermore, the ground surface around the Aira caldera was concentrically depressed by 80 cm. In order to explain these significant crustal deformations, a model consisting of a tensile fault and a deflation source is presented. By means of the least-squares fitting of the model to leveling data around the Aira caldera, we obtained the parameters of the deflation source as follows: depth 8.8 ± 1.2 km; subsidence just above the source 157 ± 27 cm. The source is located at the center of the Aira caldera. On the other hand, the tensile fault, which corresponds to the fissure craters, is estimated, on the basis of horizontal movements in Sakurajima, to be 7 km long, 1.5 km wide and 0.5 km deep at its upper margin, with an opening of 20 m. This model suggests that magma flowed out of the reservoir beneath the Aira caldera and broke the crust of Sakurajima, thus creating fissure.

A Review of Volcanic-Hazard Assesments for Active Volcanoes in Japan

A Review of Volcanic-Hazard Assesments for Active Volcanoes in Japan

新期御岳テフラ層の層序と時代 中部日本における編年上の意義

Ontake Volcano was one of the most active volcanoes in Japan, producing many extensive sheets of tephras during the late Pleistocene. These sheets are very useful for the cor- relation and chronology of the late Pleistocene deposits distributed in central Japan.The authors established the stratigraphy of the Younger Ontake tephra group by careful investigation along the Kiso valley and on the eastern foot of Ontake volcano. The Younger Ontake tephra group is classified into 17 formations by buried soils and intervening unconformities. In addition, the tephra ages are estimated using the radiometric ages of related sediments, the stratigraphic positions of widespread marker tephras, and the geologic histories of well-investigated areas in central Japan.The following are the new results obtained from this investigation.1) Among the many marker tephras originating from the Ontake volcano, Katamachi pumice layer (On-KtP) extends to the Takada coastal plain on the Sea of Japan, Ina pumice layer (On-Inp) to southern Kanto, Nagawa pumice layer (On-NgP) to the northern part of Gunma Prefecture and Tatsuno pumice layer (On-Ttp) to the Nobi plain. Therefore, these extensive pumice layers make it possible to correlate the geomorphic surfaces and the late Pleistocene deposits which are distributed in areas separated by great distances.2) The upper part of the Atsuta formation in the Nobi plain is correlated to the upper part of the Katamachi sand bed in the Takada plain. These two beds were deposited during the marine regression stage from 90, 000 to 60, 000 years ago, after the culmination of the last interglacial transgression.3) Kisogawa mudflow deposits from the Ontake and Komaki gravels in the Nobi plain are considered to have been accumulated about 45, 000 years, which makes them much older than the previously estimated age of 27, 000 years.4) The maximum phase of the Kumazawa glacial stadial in the Central Japan Alps is estimated to be older than 57, 000 years.

54B. List of the active volcanoes in Japan(Abstracts of Papers Presented at the Fall Meeting of the Society)

54B. List of the active volcanoes in Japan(Abstracts of Papers Presented at the Fall Meeting of the Society)

Evaluation methods of heat discharge and their applications to the major active volcanoes in Japan

The rates at which thermal energy is released by non-eruptive mechanisms associated with active volcanoes in Japan have been estimated from surface temperature distributions or from shapes of the fumarolic plume rise. Values of 5.3 x 10 7 W and 1.2 x 10 8 W have been calculated for non-eruptive release rates in 100-km segments of the Northeast and the Southwest Japan Arc, respectively. It appears that non-eruptive heat discharge is of the same order as that caused by eruptions.

Non-emptive thermal energy release rate from major active volcanoes in Japan.

Non-emptive thermal energy release rate from major active volcanoes in Japan.

38. Seismicity around active volcanoes in Japan(Abstracts of Papers Submitted for the Meetings of the Society)

38. Seismicity around active volcanoes in Japan(Abstracts of Papers Submitted for the Meetings of the Society)

Types of volcanic eruptions in Japan

The eruptions of volcanoes are various in surface features as well as in magnitude, depending upon their geographical position, structure, crater condition, physical and petrochemical nature of the ejecta, etc. Referring principally to the recent eruptions which occurred within the last few scores of years in Japan and which have been described in detail by the investigators, these active volcanoes in Japan are classified as shown in the tables (Tables 1 and 2). First of all, the active volcanoes are divided into two groups according to the frequency of eruption. One includes those volcanoes which are literally active with eruptions every few years; they usually have a persistent open crater from which the eruptions are taking place. Another includes those volcanoes which are usually dormant and are awakened into an eruption once in more than several scores of years; they usually have a closed crater and their next eruptions are liable to occur at new craters more or less inconsistent with the craters of the preceding eruptions. Eruptions themselves are divided first into magmatic and phreatic eruptions. The magmatic eruptions are then divided into effusive, mixed, and explosive eruptions. The effusive eruptions are rather simple, while the mixed and explosive eruptions may be further divided into certain sub-types according to the mode of occurrence of the ejecta.

Petrochemical Studies on the Active Volcanoes in Japan

Petrochemical Studies on the Active Volcanoes in Japan

The Remarkable Sunsets

THE brilliant morning and evening glows have not yet left us. In connection with a letter of one of your correspondents of December 20, 1883, it may be interesting to add that the year 1783, which was characterised by a fearful eruption of Skaptar Jokul in Iceland, and by remarkable sky-colour phenomena similar to those we have lately had, was also the year in which the last great eruption of Asama Yama in Japan took place (see Transactions of the Asiatic Society of Japan, vol. vi. part ii. P. 327). Asama Yama is the greatest active volcano in Japan. In connection also with the unusual quantity of aqueous vapour with which the atmosphere has been charged, as proved by the spectroscopic observations of Prof. Michie Smith and others, and the facility that dust particles give for the formation of clouds, and therefore also of snow, it may be interesting to note that the beginning of the present year has been characterised by the greatest fall of snow that the oldest inhabitants here have known for thirty years. The minimum temperature reached this winter (–28° C. on the morning of December 23 in the neighbourhood of the college) is also the lowest for Kingston during the same period. Prof. Goodwin is now engaged in analysing the snow in order to find out whether similar impurities to those found in Europe and in Java are present.