Dynamics of Explosive Eruptions of Changbaishan Volcano, NE China, since the late Pleistocene from the Composition and Texture of Pumice

Abstract

The explosive eruptions of Changbaishan volcano in NE China since the late Pleistocene produced large amounts of pyroclastic products, including 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 pumices and the magma characteristics reflected in the field stratigraphy, particle size, petrography, and geochemistry. We quantitatively analyzed pumice texture and placed constraints on the eruption dynamics and intensities. For the first time, the ME-Tr pumices are determined to show two colors: earth-yellow and black, which erupted in a pulsing pattern at the first stage of ME-Tr eruption. Both components 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 magma compositions and strata indicates that there may be three main crustal magma batches (ME-Com, ME-Tr-a and ME-Tr-b) of distinct compositions and temperatures were involved during the ME. The vesicle number density of the TWF pumice was the highest, as were the calculated height of the eruption column (23–32 km), and, consequently, the mass eruption rate. The eruption intensity of the ME was high during the ME-Com (24–25 km), and decreased during the ME-Tr (19–23 km). The results of this study improve our understanding of the eruption mechanisms, and the hazard assessments linked to the future Changbaishan eruptions.