Nuees ardentes and fluidization

Brown, Matthew C.

doi:10.2475/ajs.260.6.467

Cited by 15 publications

(3 citation statements)

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“…Where dense PDCs are concerned, their high mobility is commonly attributed to the influence of fluidisation of the current's particles caused by high, long-lived gas pore pressures (Sparks 1976;Wilson 1980;Druitt et al 2007;Roche 2012;Gueugneau et al 2017;Breard et al 2018). These high gas pore pressures fundamentally result from relative motion between settling particles and ascending fluid and can be produced through various processes including (i) bulk selffluidisation (McTaggart 1960;Wilson and Walker 1982), (ii) grain self-fluidisation (Fenner 1923;Brown 1962;Sparks 1978), (iii) sedimentation fluidisation/hindered settling (Druitt 1995;Chédeville and Roche 2014), and (iv) decompression fluidisation (Druitt and Sparks 1982); see Wilson (1980) and Branney and Kokelaar (2002) for reviews.…”

Section: Electronic Supplementary Materialsmentioning

confidence: 99%

Investigation of variable aeration of monodisperse mixtures: implications for pyroclastic density currents

et al. 2018

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The high mobility of dense pyroclastic density currents (PDCs) is commonly attributed to high gas pore pressures. However, the influence of spatial and temporal variations in pore pressure within PDCs has yet to be investigated. Theory suggests that variability in the fluidisation and aeration of a current will have a significant control on PDC flow and deposition. In this study, the effect of spatially heterogeneous gas pore pressures in experimental PDCs was investigated. Sustained, unsteady granular currents were released into a flume channel where the injection of gas through the channel base was controlled to create spatial variations in aeration. Maximum current front velocity results from high degrees of aeration proximal to the source, rather than lower sustained aeration along the whole flume channel. However, moderate aeration (i.e.~0.5 minimum static fluidisation velocity (U mf_st)) sustained throughout the propagation length of a current results in greater runout distances than currents which are closer to fluidisation (i.e. 0.9 U mf_st) near to source, then de-aerating distally. Additionally, although all aerated currents are sensitive to channel base slope angle, the runout distance of those currents where aeration is sustained throughout their lengths increases by up to 54% with an increase of slope from 2°to 4°. Deposit morphologies a primarily controlled by the spatial differences in aeration, where there is a large decrease in aeration the current forms a thick depositional wedge. Sustained gas-aerated granular currents are observed to be spontaneously unsteady, with internal sediment waves travelling at different velocities.

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Section: Electronic Supplementary Materialsmentioning

confidence: 99%

Investigation of variable aeration of monodisperse mixtures: implications for pyroclastic density currents

et al. 2018

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“…He observed that hot sand flows travelled further than cold ones and he hypothesized that this was due to rapid heating and expansion of the ambient cold air entrapped by the hot flows, which caused high internal turbulence. Brown (1962) argued that the high mobility of PDC could rather be due to fluidization caused by gases released by the particles and percolating upwards. Since then the concept of fluidization by gases of internal or external sources in dense PDC has received much attention from experimentalists.…”

Section: Figure 21mentioning

confidence: 99%

The contribution of experimental volcanology to the study of the physics of eruptive processes, and related scaling issues: A review

Roche

Carazzo

2019

Journal of Volcanology and Geothermal Research

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The experimental approach has become a major tool increasingly used by volcanologists in recent decades to investigate the physics of eruptive processes in complement to field and theoretical works. Researchers have developed various methodologies to study volcanic phenomena at reduced length scale. The works involve natural or analogue materials and their types range from first-order tests, to identify fundamental processes and make qualitative comparison with field observations, to more sophisticated experiments in which precise data obtained in a controlled environment can be used to validate outputs of theoretical models. Scaling is a central issue to ensure dynamic similarity between the small-scale experiments and the large-scale volcanic phenomena when natural conditions cannot be simulated due to inherent length scale difference and/or technical limitations. In this respect, dimensionless numbers are used to map physical regimes and to define scaling laws, which allow experimental results to be extrapolated to natural scale. This review presents the variety of experimental studies conducted to investigate subterraneous and aerial volcanic phenomena involving in particular fluid-particle mixtures. We focus on the major scaling issues and the physical regimes investigated, and we also highlight in a historical perspective some of the major advances achieved through experimental studies. Finally we conclude on some perspectives for future works.

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“…Brown (1962) discusses this process as one in which gases emitted by the particles develop a pressure equal to, or greater than, the hydrostatic pressure due to the weight of the particles themselves, and the mass starts to expand, and behaves like a fluid. McTaggart (1960McTaggart ( , 1962 calculated that the particles of a nuée ardente would not have enough volatiles to support themselves for appreciable distances.…”

Section: Emplacement and Mobilitymentioning

confidence: 99%

Ignimbrite Flows, Plugs, and Dikes in the Southern Part of the Hot Creek Range, Nye County, Nevada

Cook¹

1968

Geological Society of America Memoirs

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Cenozoic rocks include about 15,000 feet of continental sedimentary and volcanic rocks of Oligocene age. Volcanic rocks consist of ignimbrite flows, plugs and dikes, lavas, and air-fall tuffs.Ignimbrite plugs and dikes fill vents from which some of the surrounding ignimbrite sheets were probably discharged. Plug rocks have vitroclastic textures and textures transitional between vitroclastic and flow banding. Dike rocks have vitroclastic textures and show various stages of vesiculation. Ignimbrites forming the basal sheet are crystal-rich rhyodacites, and have less silica and alkalies than the rhyodacites forming the top sheet. The ignimbrite plugs are more siliceous and alkalic than their surface-equivalent ignimbrite sheets. These plugs are modally and chemically "stratified"; their upper parts are crystal-rich rhyodacites and contain less silica and alkalies than the basal, moderately crystal-rich rhyolites. The origin of these variations is not well understood, but available data suggest that the basal portion of a differentiating magma chamber may have been tapped, so that the magma became progressively more siliceous and alkalic; continued pulses of increasingly more siliceous material may account for the "stratification" of the plugs.Cognate crystals in the ignimbrite plugs, dikes, and sheets were broken prior to extrusion; some were broken during compaction and welding. Most of the vesiculation took place prior to extrusion. Fluidization of the constituents may account for the mobility of the ignimbrites. 107 on June 21, 2015 memoirs.gsapubs.org Downloaded from 108 STUDIES IN VOLCANOLOGYChemical compositions and textures have been modified in most sheets after they were emplaced. Secondary sanidine of a devitrification origin locally crystallized to a more sodic sanidine, and the replaced potassium may be accounted for by the K-feldspar rims on cognate crystals. Textural changes include welding, devitrification, and vapor-phase crystallization. The ignimbrite plugs and thick ignimbrite sheets are welded and devitrified from base to top. Thin sheets are welded only in their middle portions, and devitrification is confined to their upper zones. Ignimbrite plugs and their equivalent ignimbrite sheets contain vapor-phase minerals from base to top in vesicles that formed after welding. These ignimbrites were probably richer in volatiles than those in which vapor-phase crystallization was confined to the upper zones.

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Nuees ardentes and fluidization

Cited by 15 publications

References 0 publications

Investigation of variable aeration of monodisperse mixtures: implications for pyroclastic density currents

Investigation of variable aeration of monodisperse mixtures: implications for pyroclastic density currents

The contribution of experimental volcanology to the study of the physics of eruptive processes, and related scaling issues: A review

Ignimbrite Flows, Plugs, and Dikes in the Southern Part of the Hot Creek Range, Nye County, Nevada

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