As Mount Fuji looms ominously over Japan, discussions around its potential for eruption and the necessary precautions have surged, especially in light of recent volcanic activity elsewhere.
On March 21, 2025, experts convened to strategize preparedness for an impending major eruption of Mount Fuji, which could spew volcanic ash significantly affecting urban areas. With a track record of roughly 180 eruptions over the last 5,600 years, averaging an eruption every 31 years, concerns are high due to the absence of significant eruptions in over 300 years.
The catalyst for these discussions was a recent eruption of Mount Lewotobi in Indonesia, where plumes of ash soared to 16,000 meters above sea level, resulting in extensive cleanup efforts across the affected regions. Comparatively, Japan has not faced a large-scale eruption for a century, prompting experts to suggest that preparations for a similar event require immediate attention.
According to government models, if Mount Fuji erupts, south-southwest winds could direct ash toward central Tokyo, with forecasts predicting over 3mm accumulation within just three hours. By the end of the first day, central regions could witness up to 3cm of ash, with areas near Sagamihara potentially receiving an alarming 30cm or more by the end of the eruption.
Past eruptions, such as the one at Sakurajima in May 2012, serve as cautionary tales, having produced ash accumulations of about 7mm over the span of a month. Experts underscore that ash, even in small quantities, poses significant risks to daily life.
“Even a small amount (less than 1mm) of volcanic ash can halt railway operations and cause power outages or communication disruptions,” said a member of the expert panel. The expected impact of 3cm of ash could render roads impassable for two-wheeled vehicles in the rain, which is crucial for logistics throughout the city.
The government has accordingly outlined a four-stage warning system based on the amount of ashfall. During stages 1, 2, and 3, which account for ash volumes from trace levels to 30cm, remaining indoors is generally advised. However, if ash accumulates to over 3cm (stage 2 and above), those needing continuous care, such as dialysis patients, may need to evacuate to safety due to road closures and restricted movement.
Stage 4, characterized by ash thicker than 30cm, raises dire concerns, including the risk of wooden structures collapsing. Under such conditions, evacuation becomes mandatory for affected residents. The precautionary measures recommended by authorities include storing at least one week's worth of food and water and securing protective gear, like masks and goggles.
Additionally, experts advise sealing off any openings in buildings to prevent ash infiltration and recommend wearing nylon clothing, which is less prone to retaining ash particles compared to cloth. The precautionary framework aims to mitigate the impact of volcanic ash and keep citizens safe in potential crisis situations.
As Japan braces for unlikely volcanic activity, the interplay between volcanic eruptions and infrastructure highlights the critical need for readiness. Experts continue to stress that while there's no certainty that Mount Fuji will erupt, it is essential for residents to prepare for any eventuality given the current environmental context.
Thus, with an evolving situation in Indonesia and historical context underscoring the potential risks posed by Mount Fuji, it is clear that proactive measures are necessary. The possibility of significant ash fall not only threatens physical safety but could disrupt daily life and essential services, emphasizing the need for appropriate strategies and awareness among the populace.
In summary, the pressing question of how prepared Japan is for a potential Mount Fuji eruption remains, and while discussions persist, worries linger that any delay in readiness could have disastrous consequences.
