Hokkaido Official Tourism Site HOKKAIDO LOVE!

Located near the scenic shores of Lake Toya, this memorial hall reveals the remarkable history of how a flat wheat field transformed into a volcano within just a few years.

Standing before the museum is Showa-Shinzan, a volcanic dome formed by the eruptions of Mt. Usu between 1943 and 1945. Rising white steam and the mountain’s rugged reddish slopes offer a vivid reminder of the powerful forces that continue to shape Hokkaido’s landscape.

The mountain’s dramatic growth was meticulously recorded by Mimatsu Masao, a local postmaster with no formal scientific training. During World War II, when photographic film was scarce, he observed the volcano from the same location each day and carefully sketched its changing form. His work became the world-famous Mimatsu Diagram, a unique record showing the birth and growth of Showa-Shinzan through a series of precise observations. Presented at an international volcanology conference in 1948, it earned widespread acclaim from scientists around the world.

Inside the museum, visitors can view the Mimatsu Diagram alongside historical photographs and documents that trace the volcano’s creation. Standing at the foot of Showa-Shinzan while exploring these records offers a memorable opportunity to experience both the power of nature and the dedication of the man who documented it for future generations.