Jōmon Apocalypse?: What Really Happened When a Mega-Eruption Buried Southern Japan 7,300 Years Ago

About 7,300 years ago, Japan's Jōmon foraging community experienced a catastrophe. It started out small, with a few rumbles. Then came the first minor volcanic explosion, followed by a second, larger one, and a far more powerful third. Finally, the magma chamber collapsed, and pyroclastic flows and ash covered large parts of Kyushu. Forests were decimated, deer and boar populations collapsed, and, of course, the nearby Jōmon people were wiped out. An event that would rewrite Japanese prehistory. Or so the story goes.

Archaeology has long tended to paint disaster outcomes in black-and-white terms. Populations were wiped out, or they persevered. But people are far more complex than simply dying or surviving.

A new study by Enrico Crema and his colleagues tested that story. Because climate change has made disasters more frequent, understanding how past populations, such as the Jōmon, coped with disaster, and how the environment recovered, can help us better understand, manage, and recover from future disasters. But how did they test this?

Rather than relying on pottery styles, as most previous researchers had, they tried tracking the populations themselves. They used 540 radiocarbon dates, divided Japan's islands into zones, and used statistical models to compare population changes before and after the eruption. They then examined how areas buried in the thickest ash layers were affected.

And what did they find? People did not simply die, but they didn't just persevere either.

Volcanic Disasters and Japan's Jōmon

Large volcanic eruptions are wonderfully useful to archaeologists because they can precisely date what archaeologists call a 'disaster horizon' across a wide area. In other words, if you know when a volcano erupted and find that same volcano's disaster horizon in a completely different area, you can precisely date it and see whether events occurred before or after that eruption.

However, for many disasters, including volcanic ones, researchers often focus on short-term effects. Something along the lines of this:

'Oh, a volcano erupted here on Bear Island? Okay, let's see if the people of Bear Island survived. No, no sign of life after the eruption. Guess that means they all died. Cool, let's move on.'

The story frames these disasters as resulting in one of two outcomes: you collapse, or you recover. But people are not just at the whims of their environment, called environmental determinism, which dictates whether they live or die. Nor do they just stare disaster in the face and come out the other side unchanged.

Japan is well suited to test such stories. It sits in the Pacific Ring of Fire, a tectonic belt that surrounds most of the Pacific Ocean and is riddled with seismic and volcanic activity. Meanwhile, the Jōmon period is well established with a fine-grained chronology based on changes in pottery style.

But who were the Jōmon?

The Jōmon were flexible hunter-fisher-gatherers who relied on wild plants, boar, deer and aquatic resources to survive. Over time, they shifted between moving around and settling down, and they survived for thousands of years without relying on agriculture. Their name comes from the word for 'cord-marked', based on the type of pottery they made. They lived mostly in pit dwellings arranged around central open spaces. They made pottery by hand from a mix of clay, mica, talc, fibres, and crushed shells. Overall, the Jōmon people lived from around 10,500 to 300 BC, when the Yayoi largely replaced them.

A Blast From the Past

Known as the Kikai-Akahoya, or simply the K-Ah eruption, this volcanic disaster occurred around 7,300 years ago in the Kikai caldera. It originated at an undersea volcano in the East China Sea, about 30 km from mainland Kyushu. It is one of the largest Holocene eruptions, rated a 7 on the Volcanic Explosivity Index.

Although one may imagine a singular mass volcanic disaster, it was actually three explosive episodes. The first was a relatively small explosion, followed by a second that spread thick ash layers and local pyroclastic flows (surges of hot gas, ash, and rock that can travel hundreds of kilometres an hour). The third spread ash much wider and depressurised the magma chamber. Finally, the magma chamber roof collapsed, triggering massive pyroclastic flows that swept across the sea into southern Kyushu, along with major tsunamis, earthquakes, and thick ashfall.

Kyushu's subtropical forests were decimated and buried under ash. How quickly land recovered depended on ash depth and slope steepness. Less than 25 mm of ash let soil and plants return within a season; thicker layers took decades, or even centuries, to recover. Steeper slopes benefited from rain washing ash off. This ash would accumulate in valleys, floodplains and rivers. Ash-choked rivers became acidic, fish spawning beds were destroyed, and entire food chains collapsed. These local fisheries likely took decades to recover. In contrast, coastal sites likely recovered fast, helped by ocean currents.

Two prevailing views exist on what happened to the Jōmon on Kyushu. The first and more traditional view is called the Jōmon Apocalypse. According to this theory, the eruption wiped out the large forager villages of southern Kyushu. This left the area largely empty for centuries and forced the Jōmon culture to permanently relocate to eastern Japan. Supporters point to the abrupt end of major pottery traditions and the appearance of new pottery styles suggestive of newcomers from elsewhere.

The second view, called Jōmon Survival, rests on newer, better dating. It shows that Jōmon Nishinosono pottery continued right through the disaster and beyond, suggesting some local groups survived and simply continued.

The authors argue, however, that these views are simplistic and do not account for how much the Jōmon people had already changed before the disaster or how much they changed afterwards. They suggest that other climate disasters, such as sudden cold spells like the 8.2ka event, and changes in local vegetation had long ago begun changing Jōmon society. The supposed large villages had already disappeared millennia earlier, leaving only mobile hunter-gatherers in southern Kyushu by the time of the eruption. Survivors may have moved to the less-affected north of Kyushu.

To test their hypotheses, the researchers used radiocarbon dates to estimate population size. Basically, more dates mean more people. But some sites have more dates than others. To address this, researchers built statistical models to correct for that bias. They split Japan's four main islands into 61 hexagon-shaped zones and compared the 750 years before the eruption with the 750 years after.

They checked how many dates each zone had before and after the eruption and tested the models over longer and shorter time windows to see whether they produced the same results.

Then they examined ash-layer depth. More ash would indicate more damage, and thus, likely fewer people. The worst areas had ash up to 2 metres deep, especially in southern Kyushu. The researchers then added each zone's average ash depth to their population models.

In the Face of Disaster

Across most of Japan, populations grew before the eruption. In Kyushu, however, populations may have been shrinking. The eruption supposedly destroyed large villages, but they had already disappeared millennia earlier, leaving behind scattered mobile groups. In southern Kyushu, mobile groups were declining, which may have made the few remaining ones more vulnerable to disaster.

The northwest, however, was growing. Then the eruption occurred; in southern and central Kyushu, populations collapsed, but northwest coastal Kyushu kept growing. Some of that growth may have come from survivors from southern and central Kyushu travelling north.

Slit stone earrings, found only in the south before the eruption, began appearing in the north afterwards, possibly signalling incoming southern refugees. When the south was finally repopulated, people from the north likely participated, possibly alongside southern survivors.

Obsidian found at one southern site after the eruption exclusively came from Northern Kyushu. Settlements were short-lived and focused on hunting. Meanwhile, northern coastal settlements expanded their sea hunting, including to islands up to 80 km away. The authors suggest that population growth in the north may have sped up trends already underway, rather than starting them.

Interestingly, Shikoku and parts of Honshu, which usually never link to the eruption, also saw populations decline, possibly because they were in the trajectory of the ash fall.

For the most part, areas with the heaviest ashfall also saw the most severe population declines, while farther-away areas were less affected.

The results suggest that Jōmon society neither fully collapsed nor simply carried on. The eruption likely displaced large swaths of populations, added to the already growing northern population, expanded trade, and strengthened existing trade partnerships.

The findings highlight people's choices in the face of disaster and how they adapted. The Jōmon didn't simply vanish, and they didn't stubbornly stay put either. Survivors did not simply stay in the ruined south and continue their culture as before; that would have been unsustainable.

Nor did they accept their fate and simply die. They adapted, left for the coast where the environment recovered faster. They leaned on old trade and social ties and perhaps forged new ones, possibly in the form of slit stone earrings. Meanwhile, the southern interior recovered, and when they returned, they didn't just pick up where they left off; they brought new ties and a shift in the dominant culture. One inherently tied to the North.

Today, floods, wildfires, and natural disasters displace people, animals and environments. How past populations recovered, how long ancient environments took to recover, and what happened to local fauna can inform future disaster relief. It also shows us that we are adaptable; we don't just succumb to disaster, but we also can't stubbornly hold on to old ways. Where we go and how we change also shape whether we survive these disasters.

Why do you think some people chose to stay in the decimated south, and what can we learn from how past communities faced disasters like this?

Let me know what you think, and if you'd like to support this blog and the person writing it, you can chip in once, monthly, or yearly. Only if you'd like to.

References

Crema, E. R., Kuwahata, M., Uchiyama, J., Junno, A., Riede, F., & Jordan, P. D. (2026). Divergent demographic responses to the Kikai-Akahoya volcanic catastrophe in mid-Holocene Japan. Science Advances, 12(42), eaeh7197. https://doi.org/10.1126/sciadv.aeh7197

Department of Asian Art. (2002, October). Jōmon culture (ca. 10,500–ca. 300 B.C.). Metmuseum.Org. https://www.metmuseum.org/essays/jomon-culture-ca-10500-ca-300-b-c