Aira Caldera

Aira Caldera is a supervolcano in Kagoshima Prefecture, Japan, stretching roughly 23 kilometers across and forming a large depression in southern Kyushu Island. The depression sits partly beneath Kagoshima Bay, with the active Sakurajima volcano rising along its rim and emitting smoke columns regularly.

The caldera formed around 22,000 years ago through a massive eruption that covered much of southern Kyushu with volcanic material. Later eruptions shaped present-day Sakurajima, which was an island during medieval times before lava flows in 1914 connected it to the mainland.

Kagoshima city lives with daily volcanic ash that settles on streets and rooftops, swept away regularly by residents. Public washing stations stand ready for people to clean clothing and vehicles when wind carries ash into settled areas.

The bay offers several viewpoints along the coast where visitors can survey the shape of the caldera and Sakurajima volcano. Clear days bring sharper views, especially in early morning before clouds or ash build up.

Beneath the bay a magma chamber slowly expands, lifting the seafloor in places by several centimeters each year. Researchers measure this movement and use the entire area as a geological laboratory to understand volcanic behavior.