is an active complex volcano in central Honshū, the main island of Japan. The volcano is the most active on Honshū. The Japan Meteorological Agency classifies Mount Asama as rank A. It stands above sea level on the border of Gunma and Nagano prefectures. It is included in 100 Famous Japanese Mountains. Geology Mount Asama sits at the conjunction of the Izu–Bonin–Mariana Arc and the Northeastern Japan Arc. The mountain is built up from non-alkali mafic and pyroclastic volcanic rocks dating from the Late Pleistocene to the Holocene. The main rock types are andesite and dacite. Scientists from the University of Tokyo and Nagoya University completed their first successful imaging experiment of the interior of the volcano in April 2007. By detecting sub-atomic particles called muons as they passed through the volcano after arriving from space, the scientists were able gradually to build up a picture of the interior, creating images of cavities through which lava was passing deep inside the volcano. A University of Tokyo volcano observatory is located on the mountain's east slope. Volcanic gas emissions from this volcano are measured by a Multi-Component Gas Analyzer System, which detects pre-eruptive degassing of rising magmas, improving prediction of volcanic activity. There is also another mountain called Asama (朝熊山, Asama-yama) of only 555 meters in Mie Prefecture. Eruptive history The geologic features of this active volcano are closely monitored with seismographs and strategically positioned video cameras. Scientists have noted a range of textural variety in the ash which has been deposited in the region during the serial eruptions since the Tennin eruption of 1108. Tennin eruption (1108) The eruption of Mount Asama in 1108 (Tennin 1) has been the subject of studies by modern science. Records suggest that the magnitude of this plinian eruption was twice as large as that of the Tenmei catastrophe in 1783. A Swiss research team found Mount Asama's volcanic eruption could have contributed to extreme weather that caused severe famine, torrential rain and consecutive cold summers in Europe. They studied ice cores in Greenland which had increased sulfate deposition in 1108 CE. In the late Heian Period (794–1185) the diary of the court noble Fujiwara no Munetada reported that Mount Asama erupted on 29 August 1108. He wrote that a local report described rice paddies and fields could not be farmed due to being covered by a thick layer of ash. Tenmei eruption (1783) Mount