Millennium Eruption Research Articles

Phasing and climate forcing potential of the Millennium Eruption of Mt. Baekdu

The Millennium Eruption of Mt. Baekdu, one of the largest volcanic eruptions in the Common Era, initiated in late 946. It remains uncertain whether its two main compositional phases, rhyolite and trachyte, were expelled in a single eruption or in two. Investigations based on proximal and medial ash have not resolved this question, prompting us to turn to high-resolution ice-core evidence. Here, we report a suite of glaciochemical and tephra analyses of a Greenlandic ice core, identifying the transition from rhyolitic to trachytic tephra with corresponding spikes in insoluble particle fallout. By modeling annual snow accumulation, we estimate an interval of one to two months between these spikes, which approximates the hiatus between two eruptive phases. Additionally, negligible sulfur mass-independent fractionation, near-synchroneity between particle and sulfate deposition, and peak sulfur fallout in winter all indicate an ephemeral aerosol veil. These factors limited the climate forcing potential of the Millennium Eruption.

Reconstruction of the Dynamics of a Catastrophic Crater Lake Outburst Flood, Changbaishan‐Tianchi Volcano

AbstractReconstruction of the catastrophic drainage following the Millennium Eruption (ME) of Changbaishan‐Tianchi volcano in 946 ± 20 CE is of great significance, as it contributes to improving the regional maximum flood record and develop rare flood risk analysis. However, limited knowledge exists concerning the failure mode, magnitude, and transport processes of the outburst flooding. In this work, we present a whole system model that describes the paleohydrology of catastrophic drainage using geological records along the downstream valley. The model encompasses the crater lake dynamics, an approximation of the breach erosion process and flood propagation downstream. The boulder competence method was used to constrain by reasonable flow parameters, while mitigating the uncertainty caused by the ambiguous geological paleostage indicators. Paleohydrologic analysis indicates that at least 1 km3 of water was released from the caldera, with the vertical breach erosion rates as high as 34 m/hr. Volcanic activity during the ME II may have directly contributed to triggering of the flood event. The local hydrodynamic response of the downstream riverbed captures the dynamic migration patterns of sediments across spatio‐temporal scales, offering a comprehensive interpretation of the specific scouring surfaces observed in the geological profile. The analysis of simulated inundation boundaries reveals that not all recorded inundations can be attributed to the crater lake outburst event. Reconstructions of megafloods based on downstream constraints on flood stage, velocity and discharge can help to infer and constrain the dynamics of dam failure mechanisms, and also contribute to our understanding of these complex paleohydrologic events.

Climate Impacts of the Millennium Eruption of Changbaishan Volcano

AbstractThe Millennium Eruption of Changbaishan Volcano is heralded as one of the largest explosive eruptions in the Late Holocene and produced huge quantities of tephra. The petrogeochemical method estimates that the Millennium Eruption emitted up to 45 Tg of sulfur into the atmosphere—more than in the Tambora eruption in 1815 CE, which caused “a year without a summer” across the Northern Hemisphere in 1816 CE. Despite such massive emissions, evidence for this eruption's climate impact in East Asia remains elusive. To explain this contradiction, this study used 67 high‐resolution tree‐ring‐width records from the Northern Hemisphere spanning the past two millennia, complemented by volcanic sensitivity experiments conducted with the Community Earth System Model. Results reveal a prevailing decreasing/negative trend in the proxy records during the potential eruption period, with 945 CE marking the most notable negative anomaly, suggesting that the Millennium Eruption likely occurred in 945 CE rather than 946 CE. Sensitivity experiments, corroborated by proxy records, demonstrate that the Millennium Eruption induced substantial negative temperature anomalies at middle and high latitudes, alongside an increase in Meiyu‐Baiu‐Changma precipitation in the middle and lower reaches of the Yangtze River and southwestern Japan and a decrease in precipitation in India, northern China, and the South China Sea in the first post‐eruption year. This study offers a novel perspective on the climate impact of the Millennium Eruption, reconciling previous discrepancies regarding its climate impact.

A 1179-yr (417–1595 CE) tree-ring oxygen isotope chronology for northern Japan validated using the 774–775 CE radiocarbon spike

Abstract We present an annual-resolution, millennium-long tree-ring chronology for northern Japan. The chronology is based on 5309 measurements of tree-ring δ18O from 37 samples of Hiba arbor-vitae (Thujopsis dolabrata var. hondae). Although the exact geographical origin of 27 of the samples is unknown because they were extracted from excavated archaeological material, pattern matching of the tree-ring δ18O variations was robust among all 37 samples. The floating chronology constructed using all samples was cross-dated against a previously published δ18O chronology from central Japan, yielding a correlation coefficient of 0.26 (t = 9.0; p < 0.01), resulting in a temporal coverage of 417–1595 CE (i.e., 1179 yrs). The global 14C spike event at 774–775 CE was clearly recorded in the annual 14C data, which provides independent support for the dating of tree rings using oxygen isotopes. Furthermore, this δ18O chronology from northern Japan was used to successfully cross-date a wood sample buried during the “Millennium Eruption” of Baitoushan, which is located on the border between China and North Korea.

Eruption plumes extended more than 30 km in altitude in both phases of the Millennium eruption of Paektu (Changbaishan) volcano

AbstractThe Millennium Eruption of Paektu volcano, on the border of China and North Korea, generated tephra deposits that extend >1000 km from the vent, making it one of the largest eruptions in historical times. Based on observed thicknesses and compositions of the deposits, the widespread tephra dispersal is attributed to two eruption phases fuelled by chemically distinct magmas that produced both pyroclastic flows and fallout deposits. We used an ensemble-based method with a dual step inversion, in combination with the FALL3D atmospheric tephra transport model, to constrain these two different phases. The volume of the two distinct phases has been calculated. The results indicate that about 3-16 km3 (with a best estimate of 7.2 km3) and 4-20 km3 (with a best estimate of 9.3 km3) of magma were erupted during the comendite and trachyte phases of the eruption, respectively. Eruption rates of up to 4 × 108 kg/s generated plumes that extended 30-40 km up into the stratosphere during each phase.

Reassessment of the sulfur and halogen emissions from the Millennium Eruption of Changbaishan (Paektu) volcano

The 946 CE ‘Millennium Eruption’ of Changbaishan (aka Paektu) volcano ranks among the largest volcanic events of the Common Era. Its fallout represents a widespread precisely-dated marker horizon yet little is known of its environmental impacts. Here, we revisit petrologic constraints on the pre-eruptive conditions of the dominant rhyolitic magma in order to estimate the eruption's volatile budget. We show that silicic reservoirs may lose more than half of their volatile complements prior to eruption and estimate that the Millennium Eruption emitted just 2–7 Tg of sulfur and 5–10 Tg of chlorine to the atmosphere, depending on the accepted eruption magnitude. These values are lower than previous petrologic estimates but consistent with ice core glaciochemistry and tree-ring-based climate reconstructions. We further suggest that any reawakening of Changbaishan / Paektu should be heralded by enhanced CO2 emissions if driven by basalt intrusion, or by H2-H2O-rich and halogen-poor gases if resulting from evolution of a silicic reservoir. Our findings emphasise the importance of robust assessments of pre-eruptive conditions, especially in respect of temperature, when applying petrologic arguments to evaluate outgassing from silicic volcanism.

Modelling the post-caldera plumbing system of Changbaishan volcano (China) from integrated geochemical, isotopic, geobarometric, and geophysical data

The Changbaishan Tianchi volcano is the largest active volcano of China and the 946 CE VEI 6 “Millennium eruption” (ME) is responsible for the formation of its summit caldera. After the ME, the volcanic activity is characterized by smaller eruptions most of which are recorded only in historical documents. Here we analyze the deposits of the ME and 1403 CE eruption outcropping in the Heishigou section, which is located east of the Chagbaishan Tianchi caldera. We present whole-rock, glass, mineral, isotopic, and geobarometric data to obtain information on the vertical extent of the caldera and post-caldera plumbing system of the volcano. Results show that the plumbing system of the 1403 CE eruption is located between 1.9 and 5.4 km depth, which is also the depth range of the shallower reservoir of the ME. Therefore, the magma reservoir of the ME was active also after the caldera collapse. The 1403 CE magma stored in the ME reservoir evolved by fractional crystallization of the residual ME trachytic magma and underwent the contamination of upper crust material. The 1403 CE event was triggered by the injection of less evolved, mafic magma from depth. The inferred depth of the shallower ME reservoir and that of the 1403 CE eruption is the same of the present-day main geophysical anomalies (low seismic velocity and low resistivity) recorded below the Changbaishan Tianchi caldera. In addition, the source of the deformations related to the uplift during unrest episodes between 2002 and 2020 suggests a refilling of the 1403 CE plumbing system. We conclude that the plumbing system of the 1403 CE, post-caldera activity at Changbaishan Tianchi volcano is the same of the ME eruption and it is still active. This system may be recharged from the arrival of less evolved magma from depth. The proposed conceptual model of the post-caldera volcanism at Changbaishan Tianchi represents a reference framework to interpret the signals of unrest and decipher the dynamics of the present-day plumbing system.

Carbon accumulation dynamics and development processes of peatland established after the Changbaishan Millennium eruption

The Changbaishan Millennium eruption (946–947 CE) was one of the strongest volcanic activities over the past 2000 years, which greatly influenced the nearby wetland ecosystems. However, the carbon accumulation dynamics and development processes of these peatlands have rarely been investigated. This study tried to reveal the carbon accumulation dynamics and development processes of peatland established after the Changbaishan Millennium eruption. Here we selected the Yueliangwan peatland as study object. Results suggest that the Yueliangwan basin was a lake after the Changbaishan Millennium eruption. Then, a arid climate event occurred between 1250 and 1300 CE and dried out the water of this basin. During 1300–1384 years CE, the carbon accumulation rate (CAR) was low because of the peat initiation process. During 1384–1600 years CE, the CAR reached the highest over the past 700 years. Peat plants further rapidly expanded on the flat areas. During 1600–1750 years CE, the CAR showed a decreasing trend. The lateral expansion rate significantly slowed down because of the restriction of complex morphology. During 1750–1850 years CE, the CAR reached the lowest values. The lateral expansion of this peatland was over. During 1850–2019 years CE, the Yueliangwan peatland developed into bog stage. The CAR slightly increased during this period. These processes suggest that peatlands can rapidly develop after volcanic eruption. Additionally, correlation analyses indicate that regional precipitation controlled by the total solar irradiance and El Niño Southern-Oscillation (ENSO) activity played an important role in influencing the carbon accumulation dynamics and vegetation succession of the peatlands in Northeast China. This study would expand our understanding of long-term interactions between carbon accumulation dynamics and lateral expansion of peatlands, hydroclimate and volcanic activity.

Re-assessment of tree-ring radiocarbon age series for the “Millennium Eruption” of Changbaishan / Paektu volcano in relation to the precise date of 946 CE

Volcanic eruptions that are not historically attested are often dated by “wiggle matching” sequential radiocarbon measurements of the rings of trees killed by the eruption against a calibration curve. Although evidence for contamination by exposure to 14C-free geogenic carbon is well documented, it is generally assumed that the radiocarbon ages are unbiased by such “old” carbon. The ‘Millennium Eruption’ of Changbaishan / Paektu volcano (China/DPR Korea) provides an opportunity to test this assumption, since several age estimates were made before the acceptance of a precise eruption year of 946 CE. Accordingly, we develop a methodology that enables testing of assumptions and evaluation of discrepancies between reported wiggle match series. We then use it to correct for contamination levels of up to 4.5% old carbon to eight wiggle match date series for the Millennium Eruption. Without the need to discard ring ages, we find agreement indices as high as, or higher than, those for the published dates. Five of the eight series yielded high-agreement-index eruption dates closer to 946 CE than the published dates. None of the five yielded a best result without recognising some degree of contamination. Differences between the eruption dates reveal a weak association with the direction of the sampled tree from the caldera, but no relationship with distance. Our results suggest that old carbon contamination can lead to over-estimation of eruption ages by years, decades, or more. In addition, our results show that anomalously younger ages can also be a problem in radiocarbon series and these cannot be easily overcome at present by this methodology.

Cambial evidence of the “Millennium Eruption” of Changbaishan volcano (c. 946 CE) and century-scale climatic change in the Middle Ages

The Changbaishan volcano, located in northeast China, produced a large amount of charcoal during the “Millennium Eruption” (c. 946 CE). In this paper, we report a high-resolution date for the eruption using multiple methods applied to the fossil charcoal and living trees, including wood anatomy, radiocarbon dating and tree-ring cross-dating. In addition, we develop a new floating annual-resolution tree-ring chronology spanning nearly 200 years that provides information about paleoclimate conditions. In our study, we identified 60 samples of charcoal as Larix olgensis based on anatomical characteristics and geographical location. Using these materials, we dated the eruption to the winter of 946 CE based on a combination of radiocarbon dating, traditional dendrochronological cross-dating and cambial cell growth status. This allowed us to develop an L. olgensis tree-ring width chronology covering 764–946 CE and 1715–2016 CE, with significant sensitivities to April–September temperature ( p < 0.05). The tree-ring data have great potential to indicate extreme climate events; for example, we identify an extremely cold year in 903 CE. Such marker years can improve the reliability and accuracy of tree-ring data. Our study provides direct and precise tree-ring evidence for volcanic eruptions and anomalous climate years in the Middle Ages. • Cambial activity enables us to date the Millennium Eruption to winter 946 CE. • The first chronology reaching the Middle Ages so far developed in northeastern China. • The chronology was assembled from volcanic charcoal and living larch. • This chronology is sensitive to temperature.

The role of CO2 flushing in triggering the ‘Millennium’ eruption and recent unrests at Changbaishan volcano (China/North Korea)

ABSTRACT The impact of large-scale caldera-forming eruptions on our society and climate can be considerable. The triggering mechanisms of these eruptions and the instability of their magmatic systems are still elusive. Here we use X-ray tomographic microscopy, glass geochemistry and volatile element concentration data on the products of the 946 CE ‘Millennium’ eruption (ME) of Changbaishan volcano (China/North Korea) with the aim to identify the triggering mechanism of the eruption. ME emitted rhyolites and trachytes whose textural parameters suggest vesiculation events related to crystallization and magma ascent in the conduit, and to the arrival of new gas in the magmatic system. Solubility models show that the CO2 and H2O dissolved in the glass are consistent with a pressure of 100–200 MPa. Literature data from fluid inclusions in minerals indicate that the residing magma was CO2 free before the eruption, whereas the CO2 content in the glass reaches 600 ppm at the flash of the ME event. We find that a single, shallow magma reservoir localized between 7.5 and 3.7 km depth in which rhyolites occupies the top and trachytes the bottom is fully destabilized by the arrival of external CO2-rich fluids. Such fluids are released from a deeper, carbonate-rich mantle source. Our results and those of independent geophysical data show that the ME magmatic system is still active, and the continuous upraising of fluids from depth may drive unrest episodes like that recorded in 2002–2006. Our findings elucidate the role of deep, mantle-derived fluids in driving large-scale explosive eruptions. We provide evidence that volcanic unrests may not mirror the internal dynamics of magmatic reservoirs.

Late Holocene climate variability in central Korea indicated by vegetation, geochemistry, and fire records of the Yongneup moor

In many cases, proxy-based palaeoclimatic and palaeoenvironmental reconstructions in East Asia have shown mixed signatures of summer temperature and precipitation, driven by the predominant regional impact of the East Asian Summer Monsoon. Although these studies have contributed significantly to understanding the past variability in East Asian summer climate during the Holocene period, relatively little has been learned about climatic conditions in other seasons, such as winter and spring, and variations in the individual climatic elements of temperature and precipitation. To address these issues, in this study, we present a reconstruction of a 3000-year fire and vegetation history of the Yongneup moor, central Korea, during the late Holocene based on multi-proxy analyses of pollen, geochemistry, and macrocharcoal. Our data identify two fire episodes at Yongneup during ca. 2900–2700 and 2400–2300 cal yr B.P., possibly caused amid deteriorated climatic conditions not only in summer but also in winter–spring during contemporaneous grand solar minima. During the last two millennia, Yongneup likely experienced cold weather conditions at ca. 1420–1230 and 1000–590 cal yr B.P. and warm conditions at ca. 1850–1420 and 1230–1000 cal yr B.P., as well as wet conditions during ca. 1530–1400, 1220–1000, and 890–700 cal yr B.P. and drier conditions during ca. 1750–1530, 1400–1220, 1000–890, and 700–530 cal yr B.P. The dry periods were coincident with an increased El Niño–Southern Oscillation in the Tropical Pacific Ocean, which supports its role in controlling the hydroclimate of the Korean Peninsula. Our results also emphasise the potential value of further research on the “Millennium Eruption” of Mount Paektu/Changbaishan (946 CE), whose climatic consequences in the East Asian region remain poorly understood. • Late Holocene climate variability in Korea reconstructed from the Yongneup moor • Fire events coincident with solar minima at ca. 2900–2700 and 2400–2300 cal yr B.P. • Potential impact of climate deterioration on Mumun (Bronze Age) societies in Korea • Fluctuations in cold–warm and dry-wet conditions during the last two millennia • Implication on the volcanic impact of the “Millennium Eruption” of Mount Paektu

Petrochemical characteristics and geological significance of the tephra buried under peat deposits: Constrains on the Changbaishan Millennium eruption

Changbaishan Tianchi volcano is one of the most famous active volcanoes in Northeast Asia. Its Millennium eruption (ME, 946–947 CE) is considered to be one of the largest explosive eruptions over the past 2000 years, which had produced widely distributed tephra layer across Northeast Asia. However, little attention has been paid to the tephra buried in peatlands around this volcano. Here we present petrographic, geochemical and AMS14C data of the volcanic glasses within a new discovered macro-tephra layer buried in the Yueliangwan peatland, northeast China. The results suggest that buried tephra was the product of Changbaishan Millennium eruption. The eruptive sequence of the ME included comendite eruption and trachyte eruption from bottom to top. Tectonic background analyses reveal that Changbaishan Tianchi volcano regions belong to the anorogenic within plate back-arc extensional tectonic environments. Eruptive and sedimentary processes of the buried tephra were postulated as follows: a large amount of volcanic glasses formed through the eruption of trachyte magma that had high contents of rare earth elements (REE) and trace elements (TE). Then, fine grained volcanic glasses were sprayed into the atmosphere and transported to the Yueliangwan areas. The volcanic glasses deposited and formed airborne pumice layer. This buried tephra layer would act as a key isochronous marker horizon for the chronological framework in a range of sedimentary contexts across Northeast Asia. And it provides accurate eruptive sequence of Changbaishan Millennium eruption. This study would attract more attentions on the buried tephra in peatlands around active volcanoes, which would be of significance for the reconstructions of volcanic eruption history.

Where science and diplomacy meet

Mount Paektu (known as Changbaishan in China) was responsible for one of the largest eruptions in history, known as the Millennium Eruption. This cataclysm, dated through a combination of radiocarbon and ice core evidence to late 946 CE, likely formed the 5-km-wide caldera that truncates the summit of the volcano. Enclosed below this rampart lie […]

Modeling the multi-level plumbing system of the Changbaishan caldera from geochemical, mineralogical, Sr-Nd isotopic and integrated geophysical data

Changbaishan, an intraplate volcano, is characterized by an approximately 6 km wide summit caldera and last erupted in 1903. Changbaishan experienced a period of unrest between 2002 and 2006. The activity developed in three main stages, including shield volcano (basalts), cone-construction (trachyandesites to trachytes with minor basalts), and caldera-forming stages (trachytes to comendites). This last stage is associated with one of the more energetic eruptions of the last millennium on Earth, the 946 CE, VEI 7 Millennium Eruption (ME), which emitted over 100 km3 of pyroclastics. Compared to other active calderas, the plumbing system of Changbaishan and its evolution mechanisms remain poorly constrained. Here, we merge new whole-rock, glass, mineral, isotopic, and geobarometry data with geophysical data and present a model of the plumbing system. The results show that the volcano is characterized by at least three main magma reservoirs at different depths: a basaltic reservoir at the Moho/lower crust depth, an intermediate reservoir at 10–15 km depth, and a shallower reservoir at 0.5–3 km depth. The shallower reservoir was involved in the ME eruption, which was triggered by a fresh trachytic melt entering a shallower reservoir where a comenditic magma was stored. The trachytes and comendites originate from fractional crystallization processes and minor assimilation of upper crust material, while the less evolved melts assimilate lower crust material. Syn-eruptive magma mingling occurred during the ME eruption phase. The magma reservoirs of the caldera-forming stage partly reactivate those of the cone-construction stage. The depth of the magma storage zones is controlled by the layering of the crust. The plumbing system of Changbaishan is vertically extensive, with crystal mush reservoirs renewed by the replenishment of new trachytic to trachyandesitic magma from depth. Unlike other volcanoes, evidence of a basaltic recharge is lacking. The interpretation of the signals preceding possible future eruptions should consider the multi-level nature of the Changbaishan plumbing system. A new arrival of magma may destabilize a part of or the entire system, thus triggering eruptions of different sizes and styles. The reference model proposed here for Changbaishan represents a prerequisite to properly understand periods of unrest to potentially anticipate future volcanic eruptions and to identify the mechanisms controlling the evolution of the crust below volcanoes.

Large Mg[sbnd]Fe isotope fractionation in volcanic rocks from northeast China: The role of chemical weathering and magma compositional effect

This study presents Mg and Fe isotopic data for a suite of volcanic rocks including basalt, trachyte and comendite from Changbaishan, northeast China. Our results show that the Millennium Eruption (ME) trachytes and comendites have δ26Mg ranging from −0.37 to 0.14‰. Combined with literature data, the positive correlation between δ26Mg and 87Sr/86Sr ratios and the almost constant value for Nd isotopes suggest that the heavy Mg isotopic composition most likely derived from involvement of weathered products of basalt instead of the old supracrustal/basement rocks. Iron isotopic composition is significantly varied throughout our suite of samples, with δ56Fe values of 0.17 ± 0.04‰ and 0.16 ± 0.03‰ for basalts, 0.09 to 0.23‰ for cone-construction trachytes, and 0.23 to 0.37‰ for the ME samples. The slightly higher δ56Fe than MORB observed in basalts reflect the role of subducted materials that could elevate source Fe3+/ΣFe ratios via redox reaction. The trachytes from the cone construction, thought to be significantly affected by chemical weathered product, have a restricted Fe isotopic variation, while those ME samples with less weathered product input have overall higher δ56Fe values. This contrasting Fe isotopic signature suggests that the paleo-weathering event likely occurred under oxidized environment, leaving the residue with little Fe isotope fractionation. By contrast, the good correlations between Fe isotopes and indicators of magmatic differentiation (e.g., tFe2O3, SiO2, Mg#) in all rocks reflect that fractional crystallization under an open system most likely accounts for the Fe isotopic variation, which was enhanced by the compositional effect as suggested by the broadly positive relationship between δ56Fe and (Na + K)/(Ca + Mg). This study therefore highlights the potential applications of MgFe isotopes as great tracers of redox condition and ancient climate.

Zircon surface crystallization ages for the extremely reduced magmatic products of the Millennium Eruption, Changbaishan Volcano (China/North Korea)

The Millennium Eruption (ME) of Changbaishan volcano (Baitoushan, Paektu) at 946 CE (Common Era) is one of the largest explosive eruptions on Earth during Holocene times. We date unpolished zircon crystal faces from diverse ME products collected from the southern side of Changbaishan volcano where the ME pumice and welded and non-welded pyroclastic flow deposits (PFD) are better exposed. All zircons from a pumice sample of the southern caldera rim and the youngest (Group 1) zircons from a welded pumiceous PFD sample yield an isochron crystallization age of 0.7 ± 1.8 ka (2σ). Zircons from the welded pumiceous PFD sample yield additional two age groups at ~10 ka and ~ 100 ka. Zircons from a non-welded charcoal-containing PFD have only one age population at 100 ka. Our work shows that different eruption products from ME have different zircon surface age distributions and may tap different levels of a zoned felsic magma chamber. In addition, the results indicate that ion microprobe U-Th dating of zircon crystal surfaces from ME pumices can effectively date the Millennium eruption age. Previously reported zircon U-series ages for Qixangzhan eruption (12.2 ± 1.1 ka, 2σ) and Yuanchi eruption (7.3 ± 1.8 ka, 2σ) at Changbaishan are also likely to date their respective eruption ages. The occurrence of 100 ka zircons in welded and non-welded PFDs reveals an important magmatic event for the Changbaishan volcano. Zircon and Fe-rich clinopyroxene crystallized at similar temperature at 770–750 °C, indicative of early zircon crystallization in peralkaline magmas. Another important result is the extremely low oxygen fugacity (fO2 = ΔFMQ-2) of the Changbaishan samples. Minerals in ME magmas were crystallized under some of the most reducing magmatic environments on Earth. Highly reducing conditions of magmas from Changbaishan supports a continental rift setting and argues against significant involvements of subduction-related oxidizing fluids during magma genesis.

Volcanic processes and magmatic evolution of Tianchi volcano, Changbaishan

Abstract The Changbaishan volcanic field located on the Gaima (Gaema, Gaiman) Plateau has witnessed plateau-forming eruptions along with the uplift of the Gaima Plateau. The Tianchi basaltic lava shield volcano was formed at the main peak of Changbaishan, with cone construction eruptions that formed a huge and steep trachytic composite cone on the gentle lava shield. At the peak of the Millennium Eruption (ME), the height of the eruption column reached 25 km and the bulk volume of tephra was about 120 km 3 . The ME eventually formed Tianchi caldera, after which several eruptions occurred, albeit of a much smaller scale. The magmas involved in the shield-forming eruptions are characterized by both alkalic series trachybasalt and basaltic trachyandesite and subalkalic tholeiite and basaltic andesite. In the cone-construction and ignimbrite-forming eruption stages, the magma is completely composed of alkalic series trachyte and comendite. The largest negative Eu anomalies observed in ME magmas indicate that plagioclase was strongly crystallized and differentiated.

Estimating the potential risk of the Mt. Baekdu Volcano using a synthetic interferogram and the LAHARZ inundation zone

The Baekdu Volcano is located on the border between Jilin Province, China, and Ryanggang Province, North Korea. Its 946 AD eruption had a Volcanic Explosivity Index (VEI) of 7, making it among the most massive eruptions in the past 2000 years, a “Millennium eruption”. Mount Baekdu may erupt in the near future. To examine the future impact of Mount Baekdu, we generated a synthetic interferogram using a Mogi model equation to produce a simulated surface deformation phase and added simulated orbital error, topographic error, and atmospheric effects phases. We output the simulation results to the program LAHARZ, which can generate a potential hazard zone due to lahar flow. Using LAHARZ, the area affected by a Baekdu lava flow would be 4.575, 14.522, 15.866, 60.351, 404.848, 3,019.298, and 6,001.885 km2 with a VEI scale eruption of 1 to 7, respectively, while the synthetic interferogram showed that the simulated surface deformation at Mount Baekdu would be 0.04 cm, 0.1 cm, 0.7 cm, 10 cm, 1 m, 12 m, and 100 m according to the VEI category. This study can be used to estimate the interferometric synthetic aperture radar (SAR) surface deformation of Mount Baekdu and produce a hazard inundation zone map with a more certain lahar flow volume in an actual volcanic eruption and surface deformation detected using SAR images on inflation of the magma chamber.

Pyroclastic Density Current Facies in the Millennium Eruption of Tianchi Volcano, Northeast China: Insights From Topography, Stratigraphy, Granulometry, and Petrography

The 946 A.D. Millennium Eruption (ME) of Tianchi volcano produced masses of pyroclastic density current (PDC) deposits that cover an area that extends roughly 50 km from the crater. In order to understand PDC dynamic processes, this study examines the proximal to distal variations in the PDC facies by analysing the topography, stratigraphy, granulometry and petrography. Topography of Tianchi volcano has different slopes, including the cone (>6°), lava shield (2–5°) and lava plateau (20 km) are less than 10 m thick, with coarse-tail layers, ground surge layers, climbing layers, and carbonized woods in the plateau. The degree of PDC welding decreases with the distance from the crater. From the proximal to the distal strata, the emplacement temperature of the PDCs decreased from 740 °C to 280 °C. The medial layers indicate a gravitational differentiation effect and weakened transportation of the PDCs, which led to the formation of thick beds. The distal PDCs demonstrate fluidisation characteristics and a density far lower than those of the proximal and medial strata, which exhibit clear stratification. Grain size data (<64 mm) show that the median diameters decreases with increasing distance from the crater. Rhyolitic and trachytic pumice are found in the PDCs and are assumed to be associated with the composition of the magma chamber. Magmatic mixing structures were confirmed by microscope observations. The volume estimation of PDCs in China is 6.9806 km3. The PDCs exhibit characteristics of high temperatures, large volumes, flowing over long distances, and having the ability to climb hills. The PDCs were the most hazardous volcanic phenomena and can provide a reference for future potential PDC hazards around the Tianchi volcano.