Reconstructing the setting for deposition of distal tephra in the Sea of Japan Basin: A catastrophic eruption of Baitoushan Volcano

• Published in: Journal of volcanology and seismology Vol. 8; no. 4; pp. 228 - 238
• Main Author: Utkin, I. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.07.2014; Springer Nature B.V
• Subjects: Atmospheric circulation; Basins; Data processing; Earth and Environmental Science; Earth Sciences; Geochemistry; Geology; Geophysics/Geodesy; Marine; Ocean floor; Particle size; Subpopulations; Volcanic eruptions; Volcanoes; Japan; INW, Japan Sea; Tephra; Settling Velocity; Northeast Asian Study; Grain Size Distribution; Grain Size Analysis
• ISSN: 0742-0463; 1819-7108
• DOI: 10.1134/S0742046314040058

This paper presents a detailed analysis of the attitude and accumulation of fine-grain ash material from the Baegdusan-Tomakomai bed (B-Tm) on the seafloor; this material was deposited after a powerful explosion of the ultraplinian type that occurred around 938 AD. It was found that, provided one has a large digital array of grain-size analyses that characterizes both areal and vertical variability in the bed and makes use of advanced mathematical data-processing techniques (division of the grain-size distribution into subpopulations, a trend analysis of transport pathways, and so on), one can derive new information concerning the character of the eruption, its location, the pathways of aerial and marine transport, and the condition of the atmosphere and water at the time of the eruption. It was found that the grain-size distributions for the tephra in the bed in question contain information on two explosive episodes that lasted 10 days each that took place under the conditions of atmospheric circulation typical of spring (the earlier episode) and of autumn (the later episode). For both of these episodes we determined the most likely areas of ash deposition on the marine water surface. We also identified a complex structure of the areas of concentrated particle distribution on the basin bottom that reflected a vortical water structure in the Sea of Japan during the eruption.