Japan has experienced such cataclysmic events once every 10,000 years, mainly in the southern main island of Kyushu. In ancient times, supereruptions occurred in what is now the Aso Caldera in Kumamoto Prefecture and the Aira Caldera in Kagoshima Bay in Kagoshima Prefecture. In the Kikai Caldera in the sea south of Kagoshima Prefecture, a massive eruption struck 7,300 years ago, the most recent known supereruption. It sent an immense pyroclastic flow hurtling toward southern Kyushu while ashes enveloped the Japanese archipelago. As a result, local Jomon culture in the Jomon Pottery Culture Period (14500 B.C. to 1000 B.C.) was wiped out. Some studies estimate there is a 1 percent probability of a supereruption hitting Japan within 100 years. One potential site is the Kikai Caldera, where magma is believed to be filling up the chamber.