6：Abstract

 EXPLANATORY TEXT OF DISTRIBUTION MAP OF ITO IGNIMBRITE AND ASSOCIATED DEPOSITS, AIRA CALDERA, JAPAN 1:250,000
 TAKARADA Shinji*, NISHIHARA Ayumu*,**, HOSHIZUMI Hideo*, YAMASAKI Tadashi*, KANEDA Yasuaki*,*** and GESHI Nobuo*

 The distribution of Ito Ignimbrite that erupted fromAira Caldera about 30,000 years ago was compiled based on the latest research results. This report shows the present distribution of Ito Ignimbrite, together with the distributions of the altitude of the original surface of the ignimbrite deposit, 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 report also contains information on eruptive products associated with the Ito ignimbrite. The present Ito Ignimbrite is distributed up to 90 kmfromthe center of Aira Caldera. Reconstructed distribution of Ito Ignimbrite suggests that the ignimbrite reached a maximumdistance of 100 kmfromthe center of Aira Caldera. The total volume of the Ito Ignimbrite and its co-ignimbrite ash (Aira-Tn) is estimated to be 800–900 km³ (320–360 km³ in DRE).

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

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