Mount Asama erupts in 1783 (Tenmei 3),…

Mount Asama erupts in 1783 (Tenmei 3), causing widespread damage.

The three-month-long plinian eruption that begin on May 9, 1783, produces andesitic pumice falls, pyroclastic flows, lava flows, and enlarges the cone.

The climactic eruption begins on August 4 and lasts for fifteen hours, and contains pumice falls and pyroclastic flows.

The complex features of this eruption are explained by rapid deposits of coarse pyroclastic ash near the vent and the subsequent flows of lava; and these events, which are accompanied by a high eruption plume that generates further injections of pumice into the air.

The volcano's devastation exacerbates what is already known as the "Great Tenmei Famine".

Much of the agriculturally productive land in Shinano and Kōzuke provinces will remain fallow or under-producing for the next four or five years.

The effects of this eruption are made worse because, after years of near or actual famine, neither the authorities nor the people have any remaining reserves.

The August4  eruption kills up to fourteen hundred people, with an additional twenty thousand more deaths caused by the famine.