The Akahoya eruption was the strongest known volcanic eruption of the Kikai Caldera

Kikai Caldera

is a massive, mostly submerged caldera up to in diameter in the Ōsumi Islands of Kagoshima prefecture, Japan. It is the remains of the ancient eruption of a gigantic volcano....

 in Kyūshū

Kyushu

is the third largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include , , and . The historical regional name is referred to Kyushu and its surrounding islands....

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. It ejected about 150 cubic kilometres (36 cu mi) of volcanic material, giving it a 7 on the Volcanic Explosivity Index

Volcanic Explosivity Index

The Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....

. The Akahoya eruption is one of only six known eruptions reaching that magnitude during the Holocene

Holocene

The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

, or the last twelve thousand years. It dramatically changed vegetation in Southern Kyūshū.

Archaeologically it has been dated around 7,300 cal. BP

6th millennium BC

During the 6th millennium BC, agriculture spread from the Balkans to Italy and Eastern Europe, and also from Mesopotamia to Egypt. World population was essentially stable at approximately 5 million, though some speculate up to 7 million.-Events:...

 during the Earliest Jōmon period

Jomon period

The is the time in Japanese prehistory from about 14,000 BC to 300 BC.The term jōmon means "cord-patterned" in Japanese. This refers to the pottery style characteristic of the Jōmon culture, and which has markings made using sticks with cords wrapped around them...

, but it has also been radiocarbon dated

Radiocarbon dating

Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...

to 6,500 BP.