Recent progress of geophysical and geological studies of Mt. Fuji Volcano, Japan

Mt. Fuji, located in central Japan near the triple junction of the Philippine Sea, Eurasia (or Amurian), and North American (or Okhotsk) plates, is one of the arc volcanoes associated with the subduction of the Pacific plate. Mt. Fuji has unique features including an average eruption rate in the last 100,000 years of 4–6 km3/ka, which is much higher than that of other volcanoes along the same arc (0.01 and 0.1 km3/ka). Basaltic rocks dominate in Mt. Fuji, while other arc volcanoes are dominated by intermediate and felsic compositions, and Mt. Fuji has erupted both explosively and effusively, with the two largest eruptions in the last 2000 years having different styles; the 864–866 CE Jogan eruption was effusive, while the 1707 Hoei eruption, the most recent eruption, was explosive. Mt. Fuji is not only interesting from a scientific point of view, but also important from a societal point of view because it is only 100 km from the Tokyo metropolitan region, one of the biggest cities in the world hosting more than 30 million people. The Hoei eruption resulted in more than a few tens of millimeters of ashfall in Tokyo by more than 150 mm. With this background, Mt. Fuji has been studied intensively using geological and geophysical methods to understand the evolution, magma plumbing system, and current activity of the volcano. This article synthesizes the current knowledge about Mt. Fuji. In particular, we provide background information required to understand the Jogan and Hoei eruptions, and discuss how to assess the size, timing, and style of the next eruption. Statistical insights suggest that the next eruption of Mt. Fuji is more likely to be voluminous with a long precursor, given a repose time of more than 300 years.