DOI: 10.1016/j.epsl.2019.115931
论文题名: Analogue experiments on the rise of large bubbles through a solids-rich suspension: A “weak plug” model for Strombolian eruptions
作者: Oppenheimer J. ; Capponi A. ; Cashman K.V. ; Lane S.J. ; Rust A.C. ; James M.R.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 531 语种: 英语
中文关键词: analogue experiments
; conduit processes
; eruption dynamics
; source mechanism
; Stromboli
; three-phase magma
英文关键词: Bubbles (in fluids)
; Crystallinity
; Filled polymers
; Liquefied gases
; Polypropylenes
; Silicones
; Volcanoes
; Volume fraction
; Conduit process
; Crystal interactions
; Particle volume fractions
; Physical interactions
; Random close packings
; Source mechanisms
; Stromboli
; Three phase
; Suspensions (fluids)
; analog model
; bubble
; experimental study
; magma
; rheology
; slug flow
; volcanic eruption
; Italy
; Lipari Islands
; Messina [Sicily]
; Sicily
; Stromboli
英文摘要: Physical interactions between bubbles and crystals affect gas migration and may play a major role in eruption dynamics of crystal-rich magmas. Strombolian eruptions represent an end member for bubble-crystal interactions, in which large bubbles (significantly larger than the crystal size) rise through a crystal-rich near-surface magma. Indeed, volcanoes that produce Strombolian eruptions often generate ejecta with > 30 vol% (often > 45 vol%) average crystallinity. At Stromboli Volcano, Italy, average crystallinity can reach 55 vol%, which is approaching the eruptibility limit for magmas. At such high crystallinities the solids interact mechanically with each other and with bubbles. This complex rheology complicates the two-phase (liquid-gas) slug flow model often applied to Strombolian eruptions. To examine the effect of crystals on bubble rise, we performed analogue experiments in which large bubbles rise in a vertical tube filled with silicone oil and polypropylene particles. The particles have a slightly lower density than the oil, and therefore form a layer of oil + particles at the upper surface. We varied surface pressure, particle volume fraction, length of the particle-bearing cap, and bubble size to examine the ways in which these parameters influence Strombolian-type eruptions. We show that in experiments, suspended solids begin to affect bubble rise dynamics at particle volume fractions as low as 30 vol% (or, when divided by the random close packing value, a normalized particle fraction φ=0.64). Bubbles in experiments with higher particle contents deform as they rise and burst through a small aperture, generating surface fountains that begin abruptly and decay slowly, and longer-lasting acoustic signals of lower amplitude than in particle-poor experiments. Particle fractions > 38 vol% (φ>0.80) generated strong deformations on fast-expanding bubbles that applied a high stress on the cap, but they trapped bubbles that were less overpressured. Qualitatively, the gas release behavior observed in particle-rich experiments is consistent with observations of Strombolian eruptions. Moreover, we estimate that the observed crystallinity of pyroclasts at Stromboli volcano represents φ>0.8. From this we suggest a “weak plug” model for Strombolian eruptions that evolves towards a low-viscosity equivalent of Vulcanian-style plug failure with a more crystalline, stronger, and less permeable plug. Importantly, this model allows the rise of several bubbles in the conduit at the same time and suggests that longer-lasting, more pulsatory and complex eruptions may reveal an increase in near-surface crystallinity, shedding some light on changing conduit conditions that could help determine the different gas rise regimes involved in passive degassing, puffing, and different expressions of Strombolian explosions. © 2019 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165198
Appears in Collections: 气候变化与战略
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作者单位: Lamont-Doherty Earth Observatory with Columbia University, New York, United States; Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom; Department of Earth Sciences, University of Bristol, Bristol, United Kingdom
Recommended Citation:
Oppenheimer J.,Capponi A.,Cashman K.V.,et al. Analogue experiments on the rise of large bubbles through a solids-rich suspension: A “weak plug” model for Strombolian eruptions[J]. Earth and Planetary Science Letters,2020-01-01,531