Nestled in Northeast China, the Changbaishan Tianchi Volcano (CTV) and the Longgang Volcano (LGV) have long captivated the scientific community. Despite their proximity, these two volcanoes have exhibited dramatically different eruption styles, leaving researchers puzzled. However, a recent groundbreaking study has shed light on the deep-seated causes behind this intriguing phenomenon. By conducting a comprehensive 3D magnetotelluric (MT) survey, researchers have uncovered the intricate magmatic plumbing systems that govern the distinct eruptive behaviors of these two volcanoes. Magnetotelluric imaging has emerged as a powerful tool, allowing scientists to peer deep into the Earth’s crust and mantle, revealing the hidden drivers of volcanic activity. Join us as we delve into this captivating story and uncover the geophysical secrets that hold the key to understanding the divergent eruption styles of the Changbaishan and Longgang volcanoes.
the Magmatic Plumbing Systems
The Changbaishan Tianchi Volcano (CTV) and the Longgang Volcano (LGV) are both part of the Changbaishan volcanic system (CVS), a vast intraplate volcanic field in Northeast China. Despite their shared mantle-derived magmatic source, these two volcanoes have exhibited remarkably different eruptive styles, puzzling researchers for years. The CTV is characterized by a large, centralized volcanic cone and has experienced several major eruptions, including the Millennium Eruption in AD 946-947, one of the largest known post-caldera eruptions in the past 2,000 years. In contrast, the LGV is a cluster of more than 160 smaller, monogenetic volcanic cones, each with its own unique eruption history.
To unravel the mystery behind these contrasting eruptive behaviors, a team of researchers conducted a comprehensive 3D magnetotelluric (MT) survey, covering both the CTV and LGV. The MT method, which measures the Earth’s natural electromagnetic fields, has proven to be a powerful tool for imaging the subsurface electrical resistivity structure, providing insights into the presence and distribution of magma bodies.
Distinct Magmatic Plumbing Systems Revealed
The 3D MT inversion results revealed striking differences in the magmatic plumbing systems beneath the CTV and LGV. While the LGV exhibits a relatively continuous high-resistivity zone in the upper crust, indicating the absence of a shallow magma chamber, the CTV is underlain by a large, low-resistivity structure in the upper crust, which the researchers interpret as a shallow magma chamber.
This shallow magma chamber beneath the CTV, located directly below and to the northeast of the volcanic cone, extends laterally for approximately 20 x 20 km. The researchers estimate that this magma chamber contains around 12% partial melt, based on the observed low resistivity values and the high temperatures (exceeding 1,000°C) at a depth of 7.5 km.
In contrast, the LGV lacks a well-developed shallow magma chamber in the upper crust. Instead, the MT data suggest that the magma from the mantle rapidly rises through the crust, erupting at the surface with little to no residence time in a shallow crustal reservoir. This rapid ascent of uncontaminated, mantle-derived magma is likely responsible for the formation of the numerous, densely distributed monogenetic volcanic cones that characterize the LGV.
Fig. 2
Implications for Eruption Styles
The distinct magmatic plumbing systems revealed by the MT data provide a compelling explanation for the contrasting eruptive styles of the CTV and LGV. The presence of a shallow crustal magma chamber beneath the CTV allows for the magma to undergo fractional crystallization and mixing processes, leading to the evolution of more evolved, silica-rich magmas. This, in turn, facilitates the formation of the large, centralized volcanic cone and the occurrence of more explosive, potentially catastrophic eruptions, such as the Millennium Eruption.
In contrast, the lack of a shallow magma chamber in the LGV means that the mantle-derived magma ascends rapidly, erupting at the surface with minimal interaction with the crust. This results in the production of more primitive, potassic-trachybasaltic magmas, which erupt to form the numerous, smaller monogenetic cones scattered throughout the LGV field.
Fig. 3
Implications and Future Directions
The findings from this study have important implications for our understanding of intraplate volcanism and the factors that control the diversity of volcanic eruption styles. The insights gained from the 3D MT imaging of the CTV and LGV provide a valuable framework for investigating the deep-seated processes that drive volcanic activity in other intraplate settings around the world.
Moreover, the identification of a shallow magma chamber beneath the CTV, coupled with the recent seismic unrest in the region, highlights the potential for future eruptive activity at this volcano. Continued monitoring and research will be crucial for assessing the volcano’s hazard potential and informing emergency preparedness efforts in the region.
Looking ahead, the integration of these magnetotelluric findings with other geophysical, geochemical, and petrological data will further refine our understanding of the complex interplay between deep mantle processes and shallow crustal dynamics that shape the diverse volcanic landscapes of Northeast China and beyond.
Fig. 4
Author credit: This article is based on research by Lingqiang Zhao, Yan Zhan, Duygu Kiyan, Jiandong Xu, Yaxuan Hu, Ji Tang, Xiangyu Sun, Qingliang Wang, Cong Cao.
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