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The 946 eruption of Changbaishan, 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. Age of eruption has not been well constrained, but a possible age is A.D. 946[1]. The 946 eruption of Changbaishan named "Millennium eruption", and erupted about 100–120 km3 tephras.[2][3] Millennium eruption begin with strong Plinian column, and ended by voluminous pyroclastic flow. Average of 5 cm of Plinian ashfall and coignimbrite ashfall covered Sea of Japan and northern of Japan about 1.5 million km2[2], and the ash layer named "Baegdusan-Tomakomai ash"(B-Tm). Millennium eruption probably occurred in winter of A.D. 946.[4]

Age of Millennium eruption

History of 14C wiggle-matching dating

Age of eruption has not been well constrained. The earliest radiocarbon ages of the carbonized woods yielded three different ages: 1,050 ± 70 B.P., 1,120 ± 70 B.P., and 1410 ± 80 B.P.[4] 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 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.[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 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.[7][8][9][10][1]

Recent 14C wiggle-matching dating

Xu et al.,(2013)[1]reported 27 best wiggle-match dating from 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)[1] using 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.[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 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.[1] Therefore, the average of these two WM ages (A.D. 946 ± 3) represents the best modeled WM age for the Millennium eruption.[1]

History record

The book "高丽史"(History of Goryeo) describe "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) recored "十月七日夜白灰散如雪"(3 November, white ash rain as snowing) in 946 A.D.[4] The thunders may relate to Millennium eruption, and white ash rain may relate to B-Tm ash.[4] Three moths later, on 7 February(947 A.D.), "十四日，空中有聲如雷鳴"(drum thunders) and "正月十四日庚子，此日空中有声，如雷"(drum thunders) were describe in "貞信公記" and "日本紀略".[4]

Ice-core

Sun et al.,(2013)[11] found volcanic glass in Greenland, which the chemical is good agree with Millennium eruption magma(rhyolite and trachyte). The age of 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 recored.

Eruption Volume

 The eruption volume is also not been well constrained, from 70 to 160 km3. Machida et al.,1990[13] roughly estimated the proximal volume(include ignimbrite and Plinian fall) no more than 20 km3, and the volume of distal B-Tm ashfall attains more than 50 km3. The total bulk volume estimate to be 70 km3. Horn and Schmincke (2000)[2] used exponential method for minimum area/thickness and maximum area/thickness obtain the volume of Plinian ashfall is 82 ± 17 km3, and used area-thickness method for ignimbrite obtain 14.9 ± 2.6 km3. The total bulk volume estimate to be 96 ± 19 km3. Liu et al.,(1998)[3]also used same method with Horn and Schimincke to calculate the volume of Plinian ashfall, and obtain almost same value, which is 83 km3. However, Liu used different area-thickness value for ignimbrite. Liu assumed the distribution of ignimbrite is in radius 40 km of caldera, and the average ignimbrite thickness is 7.47m, which the volume of ignimbrite is 37.5 km3. The total bulk volume estimate to be 120 km3. Guo et al.,(2001)[14]used the exponential method estimate that volume of ashfall is 135.2 ± 7.8 km3. But Guo assumed the geometry of ignimbrite is a cone, and the volume of ignimbrite could be 20.1 km3. Guo also calculated the volume of valley-ignimbrite, because in a valley the thickness of ignimbrite could be 80 m. Then, the total bulk volume is 161.6 ± 7.8 km3. However, 100–120 km3 has been widely used.[15]

Eruption dynamic

 Base on sequence of pyroclastic, Millennium eruption begins with pumice and ash falls, and then eruption column collapse formed ignimbrite. The column collapse probably is pulsing collapse, because the ignimbrite and pumice-fall are interbedded. 

  1. ^ a b c d e f g h Xu, JD (2013). "Climatic impact of the Millennium eruption of Changbaishan volcano in China: New insights from high-precision radiocarbon wiggle-match dating". GEOPHYSICAL RESEARCH LETTERS. doi:10.1029/2012GL054246.
  2. ^ a b c Horn, S (2000). "Volatile emission during the eruption of Baitoushan Volcano (China/North Korea) ca. 969 AD". Bull Volcanol. doi:10.1007/s004450050004.
  3. ^ a b L'iu, RX (1998). Modern eruption of Changbaishan Tianchi volcano. China Science Pulishing. ISBN 703006285. {{cite book}}: Check |isbn= value: length (help)
  4. ^ a b c d e Hayakawa, Y (1998). "Dates of Two Major Eruptions from Towada and Baitoushan in the 10th Century". Bulletin of the Volcanological Society of Japan.
  5. ^ Dunlap, C (1996). "Physical, chemical, and temporal relations among products of the 11th century eruption of Baitoushan, China/North Korea". {{cite journal}}: Cite journal requires |journal= (help); line feed character in |title= at position 49 (help)
  6. ^ Liu, RX (1998). "The date of last large eruption of Changbaishan-Tianchi volcano and its significance". Science in China Series D: Earth Sciences. doi:10.1007/BF02932423.
  7. ^ Nakamura, F (2007). "High-precision radiocarbon dating with accelerator mass spectrometry and calibration of radiocarbon ages". The Quaternary Research.
  8. ^ Machida, H (2007). "Recent large-scale explosive eruption of Baegdusan volcano: age of eruption and its effects on society". {{cite journal}}: Cite journal requires |journal= (help)
  9. ^ Yatsuzuka, S (2010). "14C wiggle-matching of the B-Tm tephra, Baitoushan volcano, China/North Korea". Radiocarbon.
  10. ^ Yin, J (2012). "A wiggle-match age for the Millennium eruption of Tianchi Volcano at Changbaishan". Quaternary Science Reviews. doi:10.1016/j.quascirev.2012.05.015.
  11. ^ Sun, CQ (2013). "Ash from Changbaishan Millennium eruption recorded in Greenland ice: Implications for determining the eruption's timing and impact". Geophysical Research Letters. doi:10.1002/2013GL058642. {{cite journal}}: line feed character in |title= at position 82 (help)
  12. ^ Sigl, M (2015). "Timing and climate forcing of volcanic eruptions for the past 2,500 years". Nature. doi:10.1038/nature14565.
  13. ^ Michida (1990). "The recent major eruption of changbai volcano and its environmental effects". {{cite journal}}: Cite journal requires |journal= (help)
  14. ^ Guo, ZF (2001). "The mass estimation of volatile emission during 1199–1200 AD eruption of Baitoushan volcano and its significance". Science in China Series D: Earth Sciences. doi:10.1360/02yd9055.
  15. ^ Wei, HQ (2013). "Review of eruptive activity at Tianchi volcano, Changbaishan, northeast China: implications for possible future eruptions". Bull Volcanol. doi:10.1007/s00445-013-0706-5.
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