The Akahoya eruption was the strongest known volcanic eruption of the Kikai Caldera in Kyūshū, Japan. It ejected about 150 cubic kilometres (36 cu mi) of volcanic material, giving it a 7 on the Volcanic Explosivity Index. The Akahoya eruption is one of only six known eruptions reaching that magnitude during the Holocene, or the last twelve thousand years. It dramatically changed vegetation in Southern Kyūshū. Archaeologically it has been dated around 7,300 cal. BP during the Earliest Jōmon period, but it has also been radiocarbon dated to 6,500 BP.