气候变化领域集成服务门户(CCPortal): The morphology and texture of Plinian pyroclasts reflect their lateral sourcing in the conduit

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DOI	10.1016/j.epsl.2021.116844
	The morphology and texture of Plinian pyroclasts reflect their lateral sourcing in the conduit
	Trafton K.R.; Giachetti T.
发表日期	2021
ISSN	0012821X
卷号	562
英文摘要	We investigated the relationships between the size, shape, density and texture of thousands of juvenile pyroclasts from the Plinian phase of the 1060 CE Glass Mountain eruption of Medicine Lake Volcano (California, USA). Analyzed pyroclasts, which originate from representative beds of both proximal and medial deposits, range from 0.125 mm to several centimeters in diameter. We show that the size, shape, density and texture of juvenile Plinian pyroclasts are intimately interrelated: as the size of pyroclast decreases from 64 mm to 0.125 mm, their shape shifts from equant to tabular to elongate. Moreover, while rounded vesicles dominate the largest clasts, elongate and distorted vesicles become progressively more present with decreasing clast size. Concurrently, clast density continually increases in a sigmoidal way from ∼0.4 g cm−3 (>80% porous) in the largest clasts to ∼1.7–1.9 g cm−3 (20–30% porous) by 0.125 mm. These observations are identical for both the proximal and medial locations. We show that expansion, compaction and secondary fragmentation did not significantly change the texture of juvenile pyroclasts after fragmentation. The size dependency of density and texture of Plinian pyroclasts is instead interpreted to originate from the lateral position of the magma in the conduit prior to fragmentation: smaller clasts result from higher shearing closer to conduit walls, where greater shear stresses increasingly elongate vesicles and fragment particles in smaller pieces. Moreover, ∼5% of pyroclasts 1–8 mm in size are likely agglomerates of mono-texture ash particles that sintered within the conduit during or shortly after primary fragmentation. Our work shows that future studies should analyze the full spectrum of clast sizes, from the micron- to centimeter-scale, in order to fully capture the complexity and breadth of eruptive processes across the volcanic conduit. © 2021 Elsevier B.V.
关键词	conduit dynamics density Plinian pumice pyroclast terminal velocity
英文关键词	Density (specific gravity); Morphology; Particle size analysis; Shear stress; Textures; Volcanoes; California; Clast sizes; Conduit dynamic; Density; Glass mountain; Plinian; Plinian pumouse; Pyroclast; Shape density; Terminal velocity; Dynamics; clast; density; magma; morphology; plinian eruption; pyroclastic deposit; vesicle; California; Medicine Lake Volcano; United States
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203316
作者单位	Department of Earth Sciences, University of Oregon, Eugene, OR, United States
推荐引用方式 GB/T 7714	Trafton K.R.,Giachetti T.. The morphology and texture of Plinian pyroclasts reflect their lateral sourcing in the conduit[J],2021,562.
APA	Trafton K.R.,&Giachetti T..(2021).The morphology and texture of Plinian pyroclasts reflect their lateral sourcing in the conduit.Earth and Planetary Science Letters,562.
MLA	Trafton K.R.,et al."The morphology and texture of Plinian pyroclasts reflect their lateral sourcing in the conduit".Earth and Planetary Science Letters 562(2021).