Upward Magma Migration Within the Multi-Level Plumbing System of the Changbaishan Volcano (China/North Korea) Revealed by the Modeling of 2018–2020 SAR Data

Changbaishan volcano (China/North Korea border) was responsible for the largest eruption of the first Millennium in 946 CE and is characterized by a multi-level plumbing system. It last erupted in 1903 and presently consists of a cone with summit caldera. An unrest episode occurred between 2002 and 2006, followed by subsidence. Here, we analyze the Changbaishan 2018–2020 deformations by using remote sensing data, detecting an up to 20 mm/yr, NW-SE elongated, Line of Sight movement of its southeastern flank and a −20 mm/yr Line of Sight movement of the southwestern flank. This reveals an unrest occurring during 2018–2020. Modeling results suggest that three active sources are responsible for the observed ground velocities: a deep tabular deflating source, a shallower inflating NW-SE elongated spheroid source, and a NW-SE striking dip-slip fault. The depth and geometry of the inferred sources are consistent with independent petrological and geophysical data. Our results reveal an upward magma migration from 14 to 7.7 km. The modeling of the leveling data of the 2002–2005 uplift and 2009–2011 subsidence depicts sources consistent with the 2018–2020 active system retrieved. The past uplift is interpreted as related to pressurization of the upper portion of the spheroid magma chamber, whereas the subsidence is consistent with the crystallization of its floor, this latter reactivated in 2018–2020. Therefore, Changbaishan is affected by an active magma recharge reactivating a NW-SE trending fault system. Satellite data analysis is a key tool to unravel the magma dynamics at poorly monitored and cross-border volcanoes.

Evidence for old carbon contamination in ¹⁴C wiggle-match age series for the 946 CE eruption of Changbaishan volcano

Volcanic eruptions that are not historically attested are commonly radiocarbon dated by "wiggle matching" sequential 14C measurements of the rings of trees killed by the eruption against an accepted calibration curve. It is generally assumed that carbon laid down in the wood is uncontaminated by 14C-free ("old") carbon, although evidence for contamination is well documented. Often, ill-fitting ring ages are excluded from analysis. The ‘Millennium Eruption' of Changbaishan volcano on the China-DPR Korea border offers a valuable case study in wiggle match dating, since several independent groups reported age estimates before the determination and acceptance of a precise eruption year of 946 CE. Some of the discrepancies and incompatibilities between published dates were attributed to old carbon effects. Here, we apply a new methodology to correct for contamination levels of up to 4.5% old carbon to eight wiggle match date series for the Millennium Eruption. Without discarding ring ages, we find agreement indices as high as, or higher than, those for the published dates, and five of the eight date series yielded high-agreement-index eruption dates closer to 946 CE than the published dates. None of the five yield a best result at zero 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 is possible over a wide area, potentially leading to over-estimation of eruption ages by years, decades or more, cautioning against over-reliance on wiggle-match ages that are not corroborated by other lines of evidence. Our revised protocol that accounts for contamination offers a way forward in the application of wiggle match dating of eruptions and provides a platform for understanding discrepancies that exist when comparing wiggle match series.

The 2002–2005 Changbaishan Volcanic Unrest Triggered by the 2002 M 7.2 Wangqing Deep Focus Earthquake

One of the most active intraplate volcanoes in East Asia, Changbaishan volcano experienced unrest from July 2002 to July 2005. On 2002/06/28, the M 7.2 Wangqing deep-focus earthquake occurred ∼290 km northeast of Changbaishan volcano. While some studies have suggested a possible triggering relationship, the physical mechanism of such distant interaction is still not well understood. Using a template matching technique, which cross-correlates waveform of known events with continuous data, we perform systematic detection of microseismic events recorded by station CBS near Changbaishan volcano from July 1999 to July 2007. The detected earthquakes can be further categorized into three different types: volcano-tectonic (VT) events, long-period (LP) events and harmonic-spectra (HS) events. We detect 3763 VT events between July 2002 and July 2007. The intense VT earthquake swarm during the period from July 2002 to July 2005, along with recurring LPs and HSs and other geodetic/geochemical evidence, suggest magma movement during unrest. Compared with the hand-picked catalogue, the catalogue obtained by template matching technique reveals a delayed-triggering relationship between Wangqing deep-focus earthquake and unrest. The small magnitudes of the VT events and the limited numbers of LP and HS events suggest that the Wangqing mainshock likely triggered bubble excitation in the mid-crust magma system, resulting in overpressure and a small magma injection into the shallow magma chamber at a depth of ∼5 km, leading to the 3-years unrest.

A review of present-day deformation of active volcanoes in China during 1970–2013

China has numerous active volcanoes, and more than 10 erupted in the Quaternary. Although a modern eruption event has not occurred in China, the potential risk from volcanic hazards should be noted. With the development of geodetic technologies including Global Positioning System (GPS), levelling, and Interferometric Synthetic Aperture Radar (InSAR), volcanologists can now detect the present-day deformation state of China's active volcanoes. In this paper, we summarised the present-day deformation patterns, magma sources, and magma plumbing systems of China's active volcanoes during 1970-2013. The results showed that the most active volcano in China is the Changbaishan volcano, it showed significant inflation during 2002-2003, with the deformation becoming gradually weaker after 2003, indicating it had been experiencing a magma process during 2000-2010. A point source at a depth of approximately 10 km was responsible for the observed deformation. The Leiqiong volcanic field showed a trough pattern deformation during 2007-2010, which was interpreted as a dyke intrusion model. Fluctuant deformation patterns were shown in the Tengchong volcanic field. The Longgang volcanic field had experienced a volcano-wide uplift during the 1970s and 1990s. Deformation was observed in the Tatun volcanic field during 2006-2013, and two shallow sources account for the observed deformation. These volcanoes merit further monitoring given possible evidence of deformation. No obvious deformation related to volcanic activity was observed at the Ashikule volcanic field during 2003-2011. The results provide a basic introduction of the deformation state of China's active volcanoes, and may be helpful for evaluating the activity levels of China's volcanoes and mitigating the risks of future volcanic hazards.

Scenario-Based Pyroclastic Density Current Invasion Maps at Poorly Known Volcanoes: A Case Study from Changbaishan (China/North Korea)

Changbaishan volcano (China/North Korea; last eruption in 1903 AD) was responsible for a Volcanic Explosivity Index (VEI) 7 eruption in 946 AD. Approximately 186,000 people live around Changbaishan and 2,000,000 tourists/year visit the volcano. An unrest occurred between 2002 and 2006. Despite the relevant hazard, the eruptive history is poorly known, a condition common to many volcanoes worldwide. Here, we investigate the extension of the areas potentially affected by pyroclastic density currents (PDCs) in case of future eruptions following a scenario-based approach. We perform energy cone runs referred to four scenarios from columns of height 3, 10, 20 and 30 km at different vents. By using global datasets on PDCs, we produce spatial probability maps of PDCs invasion. Empirical laws between covered areas, PDC travelled distances, and heights of collapse are provided. In scenarios 3 and 4, PDCs expand at distances up to 42 km and 85 km, respectively. In scenarios 1 and 2, PDCs invade the touristic area and few main roads. Severe effects emerge from scenarios 3 and 4 with the interruption of the China–North Korea land and aerial connections and PDC. Our approach may serve as guide for the rapid evaluation of the PDC-related hazard at poorly known volcanoes.