Emplacement Temperature and Cooling Process of the AD915 Pyroclastic Flow Deposits of Towada Volcano

The emplacement temperature of the AD915 Towada pyroclastic flow (To-a pyroclastic surge) is estimated from the emplacement temperature of crusts (pumices and a lithic fragment) within the surge deposits. The measured emplacement temperature of the pyroclastic surge varies vertically in the surge deposits.  The lower part of the deposits shows low temperatures (300-500°C) because due to cooling by the cold ground surface. The middle part of the surge deposits, which was sandwiched by the lower and upper parts of the surge, shows high temperatures (350-680°C, mostly 620-650°C). The upper part of the surge deposits which was probably cooled by the atmosphere, shows moderate temperatures (less than 620°C, mostly 500-620°C).