Is Mount Fuji Active?
QUICK ANSWER
Yes, Mount Fuji is classified as an active volcano, though it has not erupted since 1707. Active means a volcano has erupted within the past 10,000 years or shows signs of being capable of erupting again. Mount Fuji is monitored continuously due to its proximity to Tokyo.
Mount Fuji's status is one of the most common questions about Japan's most famous landmark. The iconic snow-capped cone is so peaceful-looking and culturally significant that many people are surprised to learn it's an active volcano. The last eruption was over three centuries ago, but the volcanic system underneath remains very much alive. Modern monitoring keeps a close watch on Fuji because of its potential to affect over 30 million people living in the greater Tokyo region.
When did Mount Fuji last erupt?
Mount Fuji last erupted in 1707, an event known as the Hōei eruption. The eruption lasted about 16 days and produced massive amounts of ash and pumice that fell across central Japan, including in what is now Tokyo (then called Edo). The eruption was preceded by a major earthquake (the Hōei earthquake) just weeks before, demonstrating the connection between tectonic activity and volcanic eruptions in the region. The Hōei eruption created a new crater on Mount Fuji's southeastern flank, called Hōei-zan, which is still visible today. Since 1707, the volcano has been quiet.
Why is Mount Fuji considered active?
Mount Fuji is considered active because it meets the geological criteria: it has erupted in the recent past (within the last few thousand years) and shows signs of being capable of erupting again. The volcano's magma chamber is still present beneath it, and underground activity continues. Steam vents at the summit remain active. Earthquakes occur regularly around the volcano. Heat signatures and gas emissions are detected. While 'active' doesn't mean an eruption is imminent (volcanoes can be active for thousands of years between eruptions), it does mean Fuji is far from extinct.
How is Mount Fuji monitored?
Mount Fuji is one of the most heavily monitored volcanoes in the world. The Japan Meteorological Agency maintains continuous monitoring including seismographs measuring small earthquakes, GPS sensors detecting ground deformation, gas sampling stations measuring volcanic gas emissions, satellite thermal imaging detecting heat changes, and water level monitoring in nearby lakes. The dense population around Mount Fuji (over 30 million in the greater Tokyo region) makes monitoring critical. Evacuation plans exist for various eruption scenarios, with hazard maps showing potential ash fall, lava flow, and lahar paths.
When might Mount Fuji erupt again?
No reliable prediction can be made for when Mount Fuji will erupt again. The volcano has erupted multiple times historically, with gaps ranging from decades to centuries. Since the current quiet period of over 300 years exceeds many historical intervals, some volcanologists are watchful for new activity. However, volcanoes don't follow simple schedules. The 2011 Tōhoku earthquake raised concerns about stress changes affecting Mount Fuji, though no clear signs of imminent eruption have appeared since. Continuous monitoring would catch warning signs.
Mount Fuji is classified as an active volcano even though it last erupted in 1707. Its magma chamber remains beneath it, the underground system stays warm and seismically active, and another eruption is considered possible at some unknown future date. Continuous monitoring by Japan's geological agencies provides the best chance of catching warning signs before any future eruption.
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