Mount Fuji's Hoei Eruption

Mount Fuji's eruption of 1707, known as the Hoei eruption after the Japanese era name, is the volcano's most recent eruption to date. It sent ash across the Kanto region, including the shogunal capital of Edo, now Tokyo, about 100 kilometers to the northeast. The event matters because it remains the benchmark for modern planning: Japanese authorities have used it as a model for what a future Fuji eruption might do to one of the world's largest urban areas.

Fuji is a stratovolcano on the island of Honshu, built up over many thousands of years by repeated eruptions. Before 1707 it had a long record of activity, and historical chronicles describe eruptions in earlier centuries, though the last major one had occurred several hundred years before. The Hoei era fell during the Tokugawa shogunate, a time of relative peace and a growing population in Edo. Just under seven weeks before the eruption, a very powerful earthquake struck the Nankai Trough off Japan's southern coast. Many scientists think this great Hoei earthquake helped trigger the eruption by altering stresses in the crust and the volcano's magma system, though the exact mechanism is still studied.

The eruption began in the winter of 1707 and lasted roughly two weeks. It was explosive and occurred on the volcano's southeastern flank, where a new crater formed, later called Hoei-zan. Pumice, scoria, and ash were thrown high into the air and carried by the prevailing westerly winds toward the east. Near the mountain, the fall of rock and debris was heavy, burying fields and villages under thick deposits. In Edo, ash fell in a fine layer, darkening the sky at times and causing breathing problems, according to contemporary accounts. The eruption was not a lava-flow disaster, and direct deaths appear to have been limited, though records are imperfect.

The longer-term consequences were severe for farming communities near Fuji. Ash buried rice paddies and clogged rivers, leading to flooding and hardship in the following years. The Tokugawa government organized relief and ordered clearing and river work, and it levied funds from across the country to pay for recovery, a move that drew some resentment. Local residents struggled for years to restore their land.

Since then Fuji has been quiet, though it is still considered an active volcano. Japan's government has produced hazard maps and scenarios based on 1707, warning that a similar eruption today could disrupt transport, power, and communications across the Tokyo region through ash alone. The Hoei eruption thus lives on as both a historical event and a planning guide.