Aira-Tn ash layer
The Aira-Tn ash layer ( Japanese 姶 良 Tn 火山灰 , Aira-Tn-kazanbai , short: AT, English Aira-Tn tephra ) is a layer of volcanic ash that, according to calibrated radiocarbon data, was formed after the eruption of the Aira caldera about 26,000 to 29,000 years vH deposited in Kyūshū and large parts of southern Japan.
overview
The abbreviation Tn refers to the Tanzawa mountainous region , where the ash layer was first found together with pumice stone . It was only in the 1970s that it was recognized that the Aira caldera was the origin of the ash layer, after which it was called Aira Tanzawa ash layer ( 姶 良 丹 沢 火山灰 ). The ejected ash spread over a distance of 2000 km and over an oval area from Kyūshū to the Kantō region. The ash covered a total area of four million km² with a volume of approx. 150 km³. The ash layer serves as a guide horizon ( stratigraphy ) in Japanese archeology .
Ash layer thickness by region:
- from 80 cm: on the mountains of the Tottori prefecture
- from 50 cm: South Kyūshū and the western part of the Kōchi prefecture
- from 40 cm: Kyōto
- from 25 cm: at Lake Biwa
- From 20 cm: North Kyūshū, Shikoku , Chūgoku , Kinki region
- from 10 cm: Chūbu and Kantō regions
- from 5 cm: southern part of the Tōhoku region
- a few millimeters: Chiba Prefecture
- the ash layer was also detected in the northern part of the Tōhoku region and on the Korean peninsula .
annotation
- ↑ In older sources you can often find the dating 20 to 25,000 years ago. This dating was corrected using the calibrated radiocarbon data.
Individual evidence
- ↑ Akira Ono: Early Traces of Settlement: The First Humans - The Paleolithic. In: time of dawn. Catalog volume. 2004, p. 20.
literature
- Alfried Wieczorek , Werner Steinaus, Research Institute for Cultural Goods Nara (Ed.): Time of Dawn. Japan's archeology and history up to the first emperors . Catalog volume (= publications of the Reiss Engelhorn museums . Volume 10 ). Reiss-Engelhorn-Museen, Mannheim 2004, ISBN 3-927774-17-0 .
- Hiroshi Machida: Volcanos and Tephras in the Japan Area . In: Global Environmental. Research . No. 6 , 2002, pp. 19–28 (English, digital ).