Dynamics of explosive eruptions of Changbaishan volcano, NE China, since the late Pleistocene from the composition and texture of pumice

The explosive eruptions of Changbaishan volcano in NE China since the late Pleistocene produced large pyroclastic deposits, including the large ones from the Tianwenfeng (TWF) eruption, the Chifeng stage of the Millennium Eruption (ME-Com), and the Yuanchi stage of the Millennium Eruption (ME-Tr). In this study, we analyzed the differences among these deposits through the analyses of their juvenile components and consequently the characteristics of the magma reflected in the field stratigraphy, particle size, petrography, and geochemistry. We quantitatively analyzed pumice texture and constrained on the eruption dynamics and intensities. We discovered that the ME-Tr deposits contain two types of pumice characterized by two distinct colors: earth-yellow and black. These pumice erupted in a pulsating way during the first stage of the ME-Tr eruption. Both pumice types have trachyte compositions, but the SiO₂ contents of the black pumice (59.5–60.6 wt%, ME-Tr-b) are slightly lower than those of the earth-yellow pumice (62.1–63.3 wt%, ME-Tr-a). The black pumice at the Tianwenfeng summit is speculated to be a product of the late ME-Tr eruption (ME-Tr-c). The variety of the magma compositions and temperatures indicates that there may be three main crustal magma batches (ME-Com, ME-Tr-a, and ME-Tr-b) of distinct compositions and temperatures involved during the ME. The vesicle number density of the TWF pumice was the highest, as were the calculated decompression rate (0.5–3.7 MPa/s), height of the eruption column (22–37 km), and, consequently, the mass eruption rate. The eruption intensity of the ME was high during the ME-Com (as suggested by estimated column height of 24–30 km) and slightly decreased during the ME-Tr (17–29 km). The results of this study improve our understanding of the eruption mechanisms and the hazard assessments linked to the future Changbaishan eruptions.