Hokkaido Komagatake is an andesitic stratovolcano located in northern Japan. Major historic eruptions have occurred four times since the 17th century after 5000 years of dormancy. The 1640 eruption was the first and the largest eruption during historic time. The sequence of the 1640 eruption was as follows: New magma was intruded into the volcanic edifice. A first sector collapse occurred toward the south, followed by a second collapse toward the east. Blast was associated with the second collapse, and emplaced blast deposits on the surface of the (first and second collapse) debris avalanche deposit. Finally, the eruption changed to plinian phase and discharged plinian fall and pyroclastic flow. Estimated volume of the debris avalanche deposits and the pyroclastic deposits is 1.1 km³ and 2.9 km³ respectively. The southern debris avalanche lobe materials are correlated with block-and-ash flow deposits exposed at the southwest-facing amphitheater, and those of the eastern lobe are correlated with massive andesitic lava and agglutinate exposed in the east-facing amphitheater. Juvenile vesiculated andesite is commonly included within the matrix of the eastern lobe and the blast deposits, whereas the matrix of the southern lobe lacks such juvenile material. The processes of the 1640 eruption are generally similar to the 1980 eruption of Mount St. Helens.

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Miyakejima volcano is located in the Pacific, 200 km south of Tokyo, as a member of lzu-Mariana Arc active volcanoes. The main cone of the volcano has nested two calderas; outer Kuwanokitaira caldera, 4 km in diameter, and inner Hatchodaira caldera, 1.8 km by 1.6 km across. The central cone, Oyama, grew in the Hatchodaira caldera. The volcano-stratigraphy of Miyakejima during the last 7000 years was revealed and described in detail, mainly by tephrochronological method and historic records. 18 isopach maps and distribution of lavas were presented together with volume estimation of 42 erupted units. Based on the eruption-recurrence period, production rate and eruption style, the developing history was divided into four stages; 1) inactive stage of 7000-4000 yBP, 2) the Caldera-forming stage of 4000-2500 yBP, 3) the Oyama stage, from 2500 yBP to the 15th century, and 4) the Shinmio stage, 1469 A.D. to the present. The inactive stage of 7000-4000 yBP is characterized by small scale eruption with a long interval of quiescence. In the Caldera-forming stage, voluminous eruption of two accretionary lapilli and a scoria resulted in the formation of the Hatchodaira caldera. In the Oyama stage, caldera had been filled by products from central and lateral eruptions. It is noteworthy that phreato-magmatic eruptions from central vent prevail over dry magmatic eruptions. In the Shinmio stage, most eruptions took place from lateral fissures. The typical volume of materials ejected in a single eruption ranges from the order of l0^-3 km³ to 10^-1 km³ (DRE), most cases are about 10^-2 km³, and a few exceed 10^-1 km³ during the last 7000 years.

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Published experimental data on element partitioning between olivine-liquid and between plagioclase-liquid are compiled, and the thermodynamics of the element partitionings is discussed. Published thermodynamic and empirical models for the element partitioning between olivinerliquid and between plagioclase-liquid are reviewed. The parameter values obtained in the previous models are re-examined based on the experimental data compiled in this study, and the accuracies are compared in terms of the compositions of olivine and plagioclase and also the predicted equilibrium temperature. The results of comparison suggest that errors are the smallest in the models of Gee and Sack (1988) and Carmichael and Ghiorso (1990) for prediction of MgO content of olivine, Beattie (1993) model for prediction of olivine liquidus temperature, Ghiorso and Sack (1995) and Grove et al. (1992) models for prediction of CaO content of plagioclase, and Kinzler and Grove (1992) model for prediction of plagioclase liquidus temperature, respectively. For prediction of olivine and plagioclase compositions and liqudus temperature of plagioclase, Ghiorso and Sack (1995) model gives the most reliable results among the models of Nielsen and Dungan (1983), Arislkin et al. (1993) and Ghiorso and Sack (1995). It suggests that the liquid line of descent calculated by MELTS is the most accurate among the three different computer programs to simulate magma difilerentiation proceses, EQUIL, COMAGMAT and MELTS.

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Kampu volcano is a small stratovolcano situated at the central part of Oga Peninsula, Akita Prefecture. In 1810, an earthquake as large as M 6.5 occurred near this volcano. Yoshimasa Satake, the lord of the Akita clan, wrote two official reports to the Tokugawa shogunate. They included eruption records of Kampu volcano: “Yamayake” and “Yamayakekuzure”. These words were usually used for the eruption during Edo period and mean that the mountain was firing. Several reliable documents, which was written at Oga Peninsula included no eruption record. In addition, there is no eruption record in the note of Yoshimasa Satake, which is thought to have used for making the two official reports. It is concluded that the eruption descriptions of 1810 Kampu is false and created by Yoshimasa Satake at Akita clan office at Edo (Tokyo). The false eruption might have been created to make the exaggerated damage report of earthquake.

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The 1108 eruption of Asama is the largest among numerous eruptions of the volcano during the Holocene. The magnitude is twice as large as that of the notorious 1783 eruption, which killed about 1,400 people. It is also the oldest written eruption of Asama. Chuyuki, which was written in Kyoto, 300 km SW of Asama, describes that the eruption started on September 29, 1108, by the Julian calendar, and that fields of rice and other crops were severely damaged. Many fatalities are strongly suspected by the distribution of the Oiwake ignimbrite, but no description is given for human loss in Chuyuki. A thin pumice layer intercalated between the 1108 scoria and the 1783 pumice can be correlated to a record of Pele’s hair-fall in Kyoto in 1596. As many as 800 fatalities at the summit in 1598 described in Todaiki cannot be true. Tenmei Shinjo Hen’iki, which describes that a number of villages along the Jabori River were swept away by hot lahars in 1532, is not a contemporary document. It was written in the late 18th century. Fifteen fatalities at the summit in 1721 can be true. After the 1783 eruption, Asama had been relatively quiet for 100 years. During the early and middle 20th century, Asama had been very active with a peak of 398 times vulcanian explosions in 1941. About 30 Iives were lost at the summit, in the 20th century, by 12 explosions among the total about 3,000 explosions.

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The great eruption of Asama volcano in 1783 Ieft a remarkable deposit of air-fall pyroclastic materials mainly on the east-southeastern foot of the volcano. We have collected descriptions of the pyroclastic fall events of this eruption from about 190 old documents which were recently compiled and published by Hagiwara (1985-1995). The data base created from these documents amounted to ca. 980 records from which thickness data of the deposits were compiled. In this study, we compared three types of thickness data: 1) data obtained in the field, 2) directly measured data as described in old documents, 3) recalculated data from the volume of the deposit as described in old documents. Thickness data obtained in the field, 160 years (Minakami, 1942) and 210 years (Yasui et al., 1997) after the eruption coincide with each other within the limits of error. Two types of thickness data from old records show a well-established trend of sharp decrease with the distance from the vent, but the scatter of data points is so large that it is not possible to draw isopach lines over the entire deposit. Directly-measured thicknesses are about 1.7 times as large as the thicknesses calculated from the volume of the deposit, thus suggesting exaggerations in the former. Thicknesses calculated from the volume of the deposit appear about 2 times as much as the Minakami’s (1942) data suggesting possible post-depositional compaction. However, due to the lack of reliable data, both in old documents and in the measurements on historic deposits of other volcanoes, it was not possible to conclude that the post-depositional compaction plays an important role, suggesting a strong need for further research.

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