Abstract
Warm wind hole swarms were found at the top of the Yasukajigamori lava dome of the Mikurasima volcano, Japan. A white steam column with height of less than 1-2 m was seen rising from the major hole Y-a only during the depth of winter. The results of temperature and relative humidity measurements in and around the Y-a hole indicate that temperature and density of vapor in the Y-a hole strongly depend on the temperature of the outer air. This suggests air circulation involving outer air percolating through porous lava dome. Thermal energy discharged from the Y-a hole is estimated to be about 22 GJ in each year, similar to the value reported from at the Nakayama wind holes in Shimogo, Fukushima. As a result of measurements of temperature, pH and electric conductivity of water around the lava domes, we have found no evidence to suggest volcanic thermal activities. Some of wind holes at other active volcanoes could be mistaken as volcanic fumaroles.
