Jomon Adaptation to Jomon Trangression and Towada Volcanism
Disaster from the viewpoint of environmental history
The environmental history is the history of relations between human beings and environment. Studies of environmental history is actively made in USA, Canada, Oseania and so on in the world, but Japan is quite behind in the field.
Watching environmental change from the viewpoint of environmental history, I can say that environment on the earth has come in the period of active change at last. The word “unprecedented” has often been used in disasters in recent years. There is a possibility that we may often encounter “unprecedented” environmental changes which we haven’t experienced for these several hundred or several thousand years.
I think I’m going to talk about gigantic volcanic eruption in Jomon Times and the sea-level change caused by climate change. The title is “The sea, volcano and Jomon People.” This title is the same with the autumn projects exhibition of Hachinohe City Buried Cultural Properties Center Korekawa Jomon Hall for 2014 fiscal year, which shows concretely how deeply sea-level change and volcanic eruption influenced everyday life of Jomon People. I would let you understand how Jomon People lived by talking about the title.
Volcanic eruption and topography change
Figure 1 shows the sea and land distribution change in ancient Hachinohe Bay, and several times gigantic eruptions of Towada Volcano.
The climate change means temperature change occurring on a global scale. The sea-level changes by cooling and warming climate. In climate warming glaciers melt, and the water goes back to the sea, leading to higher sea-level. If climate is cooled down, the sea water turns into steam to be sent to the leeward side of prevailing westerlies, leading to become snow and ice. As a result, the sea-level becomes lower.
Where does the vapor taken up in the seas near Japan and the Pacific go? I think you understand well how the big typhoon of this year advanced. It changed the direction around Kyushu Island and advanced toward Hokkaido together with prevailing westerlies. Vapors go further around to North America and Greenland to become snow and ice. In case of the Atlantic they go to Scandinavia. We well understand it through observing gigantic trace of glacier in the past. They move together with prevailing westerlies to become a glacier on the leeward side or to melt, causing sea-level change.
Now I’ll explain figure 1.0 meter of the sea-level change is the current sea-level and I think you can understand it turns ＋20 meter or －40 meter according to the period. The sea-level change doesn’t necessarily correspond with coastline change, however. It depends upon the region how coastline change is formed.
For example, gigantic eruptions of Towada Volcano took place about 15,500 years ago. Fierce eruption took place several times and a large quantity of pumice fell down. Furthermore pyroclastic flow erupted and overflowed to every quarter. As a result the valley was filled up with 20~30 meter thick flow. A large quantity of pyroclastic flow was rapidly washed away to the sea side to fill up the lower basin for a long time.
Later, the sea-level rose to the same height with current sea-level about 8,000 years ago by rapid global warming, leading to form the ancient Hachinohe Bay and ancient Oirase Bay as gently sloping shallow tideland. That’s because a large quantity of pumice and pyroclastic flow filled up the plains.
The sea came in even to Itakura Town in Gunma Prefecture in Kanto Plains about 8,000 years ago and it was called Depths Tokyo Bay. Compared with Hachinohe area, the sea was much deeper and so a tideland wasn’t formed. Almost all shells in shell-mounds were corbicula japonica. In the same period an enclosed bay called ancient Honjo Bay was formed in Yurihonjo City in Akita Prefecture, but as a tideland wasn’t formed similarly, shells found in shell-mounds were all corbicula japonica. In ancient Oirase Bay and ancient Hachinohe Bay both of which became a tideland because they were rapidly filled up, a large number of large, fat and flabby clams, soft-shell clams and Japanese oysters were caught.
Though it’s known that a large quantity of pyroclastic flow went in Aomori Bay, almost no shell-mounds have mysteriously been discovered. Why was a resourceful tideland formed only in Hachinohe region? That’s probably because there wasn’t a small scale enclosed bay like ancient Oirase Bay. There should be more reasons but the speed to fill up plains and the sea.
The period of Jomon Transgression
The sea-level rapidly rose by climate warming from 15,000 years ago and reached the same height with current sea-level until 8,000 years ago. The sea entered landward. It is called Jomon Transgression. About 8,000 years ago in early Jomon Period Jomon Transgression reached its peak, but the enclosed bay in Hachinohe region wasn’t deep sea but a tideland. It became a gently sloping shallow tideland because a large quantity of pumice by volcanic eruption and pyroclastic flow were piled up. Such a phenomenon is unique.
Figure 2 shows Hachinohe region of about 8,000 years ago. The sea entered current basin of Oirase River this way to form an enclosed bay of ancient Oirase Bay. Ancient Hachinohe Bay and ancient Niida Bay were formed with Takadate Terrace between. We can confirm it by boring core and so on.
As important historic site of this period there are Choshichiyachi Shell-mound in Hachinohe City and Higakubo Shell-mound in Oirase Town (Figure 3). The two sites are located face to face with ancient Oirase Bay between. We can know Jomon People went to the enclosed bay and made collecting activities on the tideland. Confirming again the sites in various regions in the country which have shell-mounds in early Jomon Times, it’s been gradually known that the sea-level rose to current level about 8,000 years ago. We must revise the thought that Jomon Transgression reached its peak about 6,000 years ago.
The date of shell-mounds in early Jomon Times such as Choshichiyachi Shell-mound in Hachinohe City, Higakubo Shell-0mound in Oirase Town, Shobuzaki Shell-mound in Yurihonjo City in Akita Prefecture, Teranishi Shell-mound in Itakura Town , Gunma Prefecture, Higashi-Myo Site in Saga City is almost same between 8,000~8,200 years ago. We should consider that around the early period in Jomon Times was the peak of Jomon Transgression. So far the peak of Jomon Transgression was early to middle period in Jomon Times when settlement life prospered at Sannai-Maruyama Site. We must revise it.
Towada Volcano’s gigantic eruption took place twice and spew out Nambu pumice 9,200 years ago, and Chuseri pumice 5,900 years ago. Especially the latter was awful and a large quantity of volcanic ashes filled up the enclosed bays in Hachinohe region. As a result livelihood depending on the enclosed bays became impossible.
There is a historic site called Ichioji Shell-mound of early to middle period in Jomon Times which is located very near to Hachinohe City Buried Cultural Properties Center Korekawa Jomon Hall in Hachinohe City, Aomori Prefecture. Figure 4 shows restored landscape at that time. I think you know there is a chestnut forest in the surrounding area of living district.
I have once drawn a similar figure after I analyzed Sannai-Maruyama Site from various directions. It also had chestnut forest widely grown in the surrounding area of living district. The chestnut forest isn’t peculiar to Sannai-Maruyama Site, but it’s also the case with Hachinohe region. In other words, the living structure was that people didn’t depend on the enclosed bay environment perfectly, but they could also obtain vegetable foods in the inland area. I consider that it was agriculture and forestry and Japan has had agricultural farming since Jomon Times. People grew not annual plants like rice and wheat, but trees which continued to live for 10~20 years long.
In my opinion it is quite necessary to review whether this is special case to hold true only in Aomori Plains and Hachinohe region, or general to hold good even in Kanto Plains and other regions.
Appearance of Ento-Doki (Cylindrical potteries) culture
Regarding volcanic eruption, another important point is that the gigantic eruption of Towada Volcano which scattered Chuseri pumice made the Jomon society undergo a complete change and as a result a society with Ento-Doki culture was formed.
The first pottery of Ento-Doki culture is called Ento-Kaso-a-style. Dating it by radiocarbon dating, it was about 5,900 years ago. This matches the age of the gigantic eruption of Towada Volcano. Ento-Doki hasn’t been unearthed from the lower soil of erupted volcanic ashes.
Figure 5 compares the vegetation of Sannai-Maruyama Site, Ooyazawa-noda Site of the same period in Aomori City, and Tashirotai in Hakkoda Mountains where there is no trace for human beings to live.
First of all, please look at Hakkoda Mountains. The beech forest became catastrophic by volcanic eruption and was replaced by deciduous oak forest. I think you know it took as many as 400 years for beech forest to be restored.
Then how about Sannai-Maruyama Site and Ooyazawa-noda Site at that time? We know chestnut forest spread out at a stretch. Such a change continued without intermission for as many as 1,900 years. Speaking from ecological common sense, such a chestnut forest is absolutely impossible in nature. I think we can say that people living here must have managed and maintained the chestnut forest.
Chestnut forest spread out in Hachinohe region, too, soon after the gigantic eruption. There is a high possibility that the similar situation was created in a pretty wide range including Tohoku District. It depends upon the investigation to be made from now on that it will probably be known that the phenomenon characterizes Ento-Doki culture.
Checking the number of historical sites before and soon after the gigantic eruption, we know the latter increased suddenly and sharply. A central settlement such as Sannai-Maruyama Site was formed and the scale of settlement became larger. Above all Ento-Doki culture was suddenly established and the number of unearthed potteries increased incomparably.
People were attacked by the gigantic eruption of Towada Volcano about 5,900 years ago in Jomon Times. I think it’s common to consider that the population decreased as people suffered a catastrophic blow. But the fact is quite different. Soon after the eruption, Ento-Doki culture appeared and the range of distribution expanded at a stretch from northern Tohoku District to southern Hokkaido. The fact is that they fell a victim to a disaster. Why did such a thing occur? Regarding it, archaeology and peripheral science like environmental studies haven’t considered earnestly. There is a possibility that various kinds of people came in from other regions to make new families and society. Additionally the population may have sharply increased. People on the continent which was located far away could probably confirm the gigantic eruption. What kind of change occurred in Jomon society after the gigantic eruption? What at all does it mean to overcome the disaster? As of now, I can’t say anything except mystery.
(Translated by Junzo Miyamoto)