Tianchi eruption
| Millennium (Tianchi) Eruption | |
|---|---|
| Volcano | Paektu Mountain |
| Date | 946 |
| Type | Plinian eruption |
| VEI | 7 |
| Impact | At least short-term regional climate changes |
The 946 eruption of Paektu Mountain, on the boundaries of China/Korea, was one of the most powerful in recorded history and is classified as a VEI-7 event. The eruption resulted in a brief period of significant climate change in China. The date of the eruption has not been precisely determined, but a possible date is A.D. 946.
The 946 eruption of Paektu Mountain has been dubbed the "Millennium eruption" or the "Tianchi eruption", and erupted about 100–120 km3 (24 to 28.8 cubic miles) of tephra. The eruption began with a strong Plinian column, and ended with voluminous pyroclastic flows. An average of 5 cm of Plinian ashfall and coignimbrite ashfall covered about 1.5 million km2 of the Sea of Japan and northern Japan. This ash layer has been named the "Baegdusan-Tomakomai ash"(B-Tm). It probably occurred in the winter of A.D. 946. This was one of the largest and most violent eruptions in the last 5000 years along with the Hatepe eruption of Lake Taupo at around 180 AD and the 1815 eruption of Tambora.
In 2017 it was found that by cross-referencing tree ring analysis with ash deposits found in ice cores drilled in northern Greenland, the eruption occurred in the last 2 or 3 months of 946 AD.
In 1996, Dunlap reported a high-precision wiggle-matching age determined at the University of Arizona as 1039 ± 18 AD(2σ). However, in 1998, Liu reported a 14C measurements from the center to the edge of the wood, followed by fitting with a high-accuracy tree ring calibrating curve, the obtained age of the Millennium eruption was determined to be 1215 ± 15 AD. In 2000, Horn reported another wiggle-matched radiocarbon dating with an AMS-mass spectrometer, and the interval of highest probability is 969 +24/-15 AD(945–984 AD; 2σ), which is widely used. In the 2000s, at least 5 of high-precision 14C wiggle-matching ages had been reported: 930–943 AD, 926 ± 10 AD, 945–960 AD, 931 ± 10 AD, and 946 ± 6 AD.
Xu et al.,(2013) reported 27 best wiggle-match datings from a single partially charred 264-year-old tree, which is 946 ± 3 AD(1σ). Yin et al.,(2012) also reported 82 best wiggle-matched AMS 14C ages of samples from four carbonized logs, which is 938/939. However, the result of Xu et al. (2013) used a “regional 14C offset” in their ages to decrease the error, and their new date was obtained from the longer tree-ring sequence with the higher analytical precision of ±25 14C years, on a 260-year tree-ring sequence that covers three consecutive wiggles around A.D. 910, A.D. 785, and A.D. 730. Since longer dated tree-ring sequence, finer sample resolution, and higher 14C analytical precision all facilitate more and tighter tie-points for better WM dating. The new date is believed to represent yet the best high-accuracy and high-precision 14C WM chronology for the Millennium eruption. Xu's wood samples were cut from a tree growing in the area about 24 km from the vent of Changbaishan volcano, it is not clear if volcanic CO2 emission before the eruption could affect the samples and produce ages that are slightly too old. The best WM dates for the Millennium eruption use the outliers-removed subset of the original 14C measurements and also account for the effect of possible regional 14C offset, and yielded two nearly identical WM ages of A.D. 945 ± 3 and A.D. 947 ± 3, where overall and combined agreement indices of the models reach their highest values. Therefore, the average of these two WM ages (A.D. 946 ± 3) represents the best modeled WM age for the Millennium eruption.
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