Remote sensing of high temperature on the slope of Mt. Unzen-Fugendake volcano by infrared thermometer

A remote sensing method was applied for estimating temperatures on the slope of Unzen-Fugendake volcano by a visual type infrared thermometer. The maximum values of surface temperatures on the northeast slope were 195°C on 18 October 1991, 138°C on 13 March 1992 and 134°C on 22 January 1993. The surface areas of elevated temperature (>50°C) were estimated to be 149000 m² on 18 October 1991 and 99000 m² on 22 January 1993. The maximum values of surface temperatures on the east slope were 131°C on 18 October 1991, 215°C on 13 March 1992 and 185°C on 22 January 1993. The surface area of elevated temperature (>100°C) were estimated to be 956000 m² on 8 January 1992, 632000 m² on 3 April 1992 and 62000 m² on 22 January 1993. The high temperature area (>1OO°C) expanded rapidly due to pyroclastic flows. The decreasing rate of surface temperatures of pyroclastic flow were 3.9°C/min in the period of 2~12 minutes after the pyroclastic flow and 2.4°C/min in the period of 17-24 minutes