946 eruption of Paektu Mountain

946 eruption of Paektu Mountain
VolcanoPaektu Mountain
Datepossibly 946 (precise year unknown)
TypePlinian eruption
LocationJilin, China and Ryanggang Province, North Korea
VEI7
ImpactAt least short-term regional climate changes

The 946 eruption of Paektu Mountain, also known as the Millennium Eruption or Tianchi eruption, 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 Manchuria. The year of the eruption has not been precisely determined, but a possible year is A.D. 946.[1]

The eruption ejected about 100–120 cubic kilometres (24–29 cu mi) of tephra[2][3] and collapsed the mountain into a caldera, which now contains the crater lake Heaven Lake. The eruption began with a strong Plinian column, and ended with voluminous pyroclastic flows. An average of 5 cm (2.0 in) of Plinian ashfall and coignimbrite ashfall covered about 1,500,000 km2 (580,000 sq mi) of the Sea of Japan and northern Japan.[2] This ash layer has been named the "Baegdusan-Tomakomai ash"(B-Tm). It probably occurred in winter in late A.D. 946.[4] 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, the 1257 eruption of Mount Samalas near Mount Rinjani, and the 1815 eruption of Mount Tambora.

Age

History of 14
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wiggle-matching dating

In 1996, Dunlap reported a high-precision wiggle-matching age determined at the University of Arizona as 1039 ± 18 AD(2σ).[5] However, in 1998, Liu reported 14
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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.[6] 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 high-precision 14
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wiggle-matching ages had been reported: 930–943 AD, 926 ± 10 AD, 945–960 AD, 931 ± 10 AD, and 946 ± 6 AD.[1][7][8][9][10]

2013 14
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wiggle-matching dating

Xu et al.,(2013)[1] 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 14
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ages of samples from four carbonized logs, which is 938/939. However, the result of Xu et al. (2013)[1] used a "regional 14
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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 14
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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 14
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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 14
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WM chronology for the Millennium eruption.[1] 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.[1] The best WM dates for the Millennium eruption use the outliers-removed subset of the original 14
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measurements and also account for the effect of possible regional 14
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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.[1] Therefore, the average of these two WM ages (A.D. 946 ± 3) represents the best modeled WM age for the Millennium eruption.[1]

Historical records

The book Goryeosa (History of Goryeo) describes "是歳天鼓鳴赦" and "定宗元年天鼓鳴" (thunders from the heaven drum) in 946 A.D. Also, the book «興福寺年代記» (Heungboksa Temple History) records "十月七日夜白灰散如雪" (3 November, white ash rain as snowing) on 3 Nov 946.[4] The thunders may relate to the Millennium eruption, and white ash rain may relate to B-Tm ash.[4] Three months later, on 7 February (947 A.D.), "十四日,空中有聲如雷鳴" (On the 14th, the air sounded like thunder) and "正月十四日庚子,此日空中有声,如雷" (On the 14th of the first month of Gengzi, there was a sound in the sky, like thunder) were recorded in «貞信公記» and «日本紀略».[4] Another similar record is on 19 Feb 944, in «日本紀略» "廿三日丙申,子刻,振動,聲在上" (On the three days of Bingshen, Zi En, vibration, sound in above).[4] Based on the historical record, the eruption may have started on February 944 or November 946, reaching a climax in February 947.[4]

Ice-core

Sun et al.,(2013)[11] found volcanic glass in Greenland, which could well have originated in the Millennium eruption magma (rhyolite and trachyte). The age of the volcanic glass layer is 939/940 A.D. However, Sigl et al.,(2015)[12] found out that ice-core chronologies are 7 years offset, and the Millennium eruption glass layer should be in 946/947 A.D. This conclusion is consistent with wiggle-matching dating and history records.

Multi-proxy dating

Oppenheimer et al., (2017)[13] A radiocarbon signal of 775 CE in a subfossil larch engulfed and killed during the initial explosive eruption, combined with glacial evidence from Greenland, dates the eruption to late 946 CE. This date rules out the Millennium Eruption contribution to the collapse of the Balhae in 926 CE. They also did not see a consequent cooling signal in tree-ring-based reconstructions of Northern Hemisphere summer temperatures. The new date focuses attention on the chronicle from a temple in Japan that reports "white ash falling like snow" on 3 November 946 AD.[14]