6：Abstract

 EXPLANATORY TEXT OF DISTRIBUTION MAP OF ASO-4 IGNIMBRITE AND ASSOCIATED DEPOSITS, ASO CALDERA, JAPAN

1:250,000

 HOSHIZUMI Hideo*, TAKARADA Shinji*, MIYABUCHI Yasuo*,**, MIYAGI Isoji*, YAMASAKI Tadashi*, KANEDA Yasuaki*,*** and GESHI Nobuo*

 The distribution of Aso-4 Ignimbrite that erupted fromAso Caldera about 90,000 years ago was compiled based on the latest research results. This report shows the present distribution of Aso-4 Ignimbrite together with the distributions of the altitude of the original depositional surface of the ignimbrite, the thickness of the ignimbrite deposit, the maximumdiameters of pumice and lithic fragments, and the alignment of the pumice clasts in the ignimbrite deposit. The present Aso-4 Ignimbrite covers wide area in the northern-central part of Kyushu Island. Distribution of the ignimbrite can be traced up to 〜170 kmNE fromthe center of the caldera. The total volume of the erupted magma during the eruption is estimated as 465–960 km³ in dense rock equivalent (DRE), including 225–590 km³ DRE of Aso-4 Ignimbrite, and 240–370 km3 DRE of Aso-4 Ash. This value corresponds to VEI 8.

*Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, AIST **Kumamoto University ***Ibaraki University

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