RECONSTRUCTION OF THE PALEOCONE MORPHOLOGY OF CHANGBAISHAN TIANCHI VOLCANO
Calderas,large basin-shaped landforms created by massive explosive eruptions,leave behind"pot-like"structures that can provide essential insights into the history and processes of volcanic development and associated hazards.The Changbaishan Tianchi caldera,located on the Sino-North Korean border in eastern Jilin Province,China,is one of the best-preserved large Cenozoic composite active volcanoes in China.This caldera,close to the Wangtiane and Baotaishan volcanoes to the south and southeast,sits atop a basalt plateau,reaching a peak elevation of 2 749m.Its formation involved multiple phases of overflow eruption activities,followed by caldera collapse due to explosive eruptions and pressure loss within the crustal magma chamber during the late Pleistocene.Over time,glaciers and flowing water have sculpted its surroundings,creating U-shaped valleys along the caldera rim.The structure and formation processes of its paleocone have thus attracted significant attention.In this study,we drew from reconstruction techniques applied to similar calderas globally.Starting with a focus on the volcanic cone profile,we identified large-scale stratovolcanoes with symmetrical cone shapes akin to Changbaishan Tianchi for comparison.Using high-resolution stereo imagery,we extracted a Digital Elevation Model(DEM)with remote sensing software.From these DEMs,we performed detailed topographic analysis,calculating and statistically modeling geomorphological parameters,which allowed us to develop a three-phase empirical model of cone topography.Applying a moving surface algorithm in MATLAB,we generated surface equations for each volcano profile,revealing quantitative relationships between pixel position,coordinates,and elevation in 3D geographic space.We then used ArcGIS's Kriging interpolation method to create a DEM of the reconstructed cone of Changbaishan Tianchi volcano,allowing us to approximate the original cone structure.The results estimate the original Changbaishan Tianchi cone reached a height of 4,100m,with a crater diameter of about 390m and a depth of 170m.The cone displayed a funnel-like structure at the summit,with slopes characteristic of stratovolcanoes.The inner edge of the cone had a relatively uniform slope,while the upper outer edge was steep,averaging 27°,and the lower outer slope angle decreased to an average of 18.5°.These parameters align with typical stratovolcano profiles.The explosive eruptions and subsequent cone collapse are estimated to have led to a volume loss of approximately 28.92km3.This paleocone reconstruction of Tianchi volcano enhances our understanding of the history of the development and evolution of Tianchi volcano,contributing valuable data for reconstructing similar caldera cones and examining eruption mechanisms within the Changbaishan volcanic field.Moreover,this study provides critical information for analyzing the geological history of Tianchi volcano,including the formation of glacial landforms and processes related to eruptions and natural disasters.
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