Erosion, transport and segregation of pumice and lithic clasts in pyroclastic flows inferred from ignimbrite at Lascar Volcano, Chile

Calder, Eliza S.; Sparks, R. S. J.; Gardeweg, M.

doi:10.1016/s0377-0273(00)00207-9

Cited by 143 publications

(129 citation statements)

References 41 publications

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“…In addition, Fan and co-workers [86,89,90] have studied segregation in two-dimensional bounded heaps with fluid and solid-like regions. An incompressible bulk velocity field is determined from DPM simulations, and subsequently used in the computation of the resulting grain-size distribution using the bidisperse segregation equation (26) with an extended diffusive term. This approach produces very good results that explain the segregation pattern in heaps in a continuously depositing regime, but it is unable to capture flow transitions that lead to stratification patterns [3,7,58,91].…”

Section: Segregation In Bidisperse Mixturesmentioning

confidence: 99%

“…2(e) with a Péclet number equal to 19. Wiederseiner et al [92] used a standard Galerkin finite element method programmed in the pdepe routine in Matlab to solve the two-dimensional steady-state segregation equation (26) and hence determine an appropriate segregation rate S ls to match the experimental data. This solution is shown in Fig.…”

Section: Segregation In Bidisperse Mixturesmentioning

confidence: 99%

“…[1,20,21,30,78,80,81,83]). For instance, neglecting cross-slope terms in (26) and using Leibniz' integral theorem, together with the surface and basal kinematic and no flux (23) conditions, implies that the depth-averaged segregation equation is…”

Section: A Depth-averaged Segregation Modelmentioning

confidence: 99%

See 2 more Smart Citations

Debris flows: Experiments and modelling

Turnbull

Bowman

McElwaine

2014

Comptes Rendus. Physique

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Section: Segregation In Bidisperse Mixturesmentioning

confidence: 99%

Section: Segregation In Bidisperse Mixturesmentioning

confidence: 99%

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Debris flows: Experiments and modelling

Turnbull

Bowman

McElwaine

2014

Comptes Rendus. Physique

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“…Rounding of pumice clasts is often interpreted as evidence for transport in pyroclastic density currents (e.g., Wilson and Hildreth 1998), hence clast shape may preserve information about the transport processes within currents. Particle roundness is expected to increase with transport distance in density currents, and significant rounding of clasts is often found in distal deposits (e.g., Calder et al 2000) and in pumice lobes (e.g., Pittari et al 2005). In some deposits there is enough variability in clast roundness and shape to distinguish among genetic processes and elucidate transport dynamics (Dellino and Volpe 1996).…”

Section: Introductionmentioning

confidence: 99%

Rounding of pumice clasts during transport: field measurements and laboratory studies

2010

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Volcanic clasts in many pyroclastic density current deposits are notably more round than their counterparts in corresponding fall deposits. This increase in roundness and sphericity reflects different degrees of comminution, abrasion and breakup during transport. We performed experimental measurements to determine an empirical relationship between particle shape and mass loss caused by particle-particle interactions. We consider, as examples, pumice from four volcanoes: Medicine Lake, California; Lassen, California; Taupo, New Zealand; Mount St Helens, Washington. We find that average sample roundness reaches a maximum value once particles lose between 15% and 60% of their mass. The most texturally homogeneous clasts (Taupo) become the most round. Crystal-rich pumice abrades more slowly than crystal-free pumice of similar density. Abrasion rates also decrease with time as particles become less angular. We compare our experimental measurements with the shapes of clasts in one of the May 18, 1980 pyroclastic density current units at Mount St Helens, deposited 4-8 km from the vent. The measured roundness of these clasts is close to the experimentally determined maximum value. For a much smaller deposit from the 1915 Lassen eruption, clast roundness is closer to the value for pumice in fall deposits and suggests that only a few volume percent of material was removed from large clasts. In neither field deposit do we see a significant change in roundness with increasing distance from the vent. We suggest that this trend is recorded because much of the rounding and ash production occur in proximal regions where the density currents are the most energetic. As a result, all clasts that are deposited have experienced similar amounts of comminution in the proximal region, and similar amounts of abrasion as they settle through the dense, nearbed region prior to final deposition.

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“…Grigorian et al 1967, Kulikovskii & Eglit 1973, Eglit 1983, Savage & Hutter 1989, Gray et al 1999, Gray et al 2003, which all assume that the material is incompressible and the pressure is lithostatic. It is therefore possible to envisage coupled models to explain some of the complex feedback mechanisms that particle-size segregation can have on both geophysical flows Particle size segregation in dense shallow granular free-surface flows 3 (Pouliquen et al 1997, Pouliquen & Vallance 1999, Calder et al 2000, Iverson 2003) and in industrial rotating drums and kilns (Zik et al 1994, Hill & Kakalios 1995.…”

Section: Introductionmentioning

confidence: 99%

A three-phase mixture theory for particle size segregation in shallow granular free-surface flows

2006

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Particle-size segregation within granular materials is of great technological significance yet it is still very poorly understood. There are several causes for segregation, but this paper focuses on kinetic sieving which is the dominant mechanism in dense gravity-driven shallow free-surface flows, or, granular avalanches. The segregation model is derived from a three-phase mixture theory composed of large particles, small particles and a passive interstitial fluid. Steady-state solutions are constructed for a normally graded inflow in a steady uniform flow field. This problem is of fundamental interest, because it shows how an unstably stratified layer readjusts into a stable configuration. Expansion fans and concentration shocks are generated and sufficiently far downstream inversely-graded segregated layers form, with the larger particles overlying the finer ones. The distance for complete segregation to occur is shown to increase with rising fluid density and tends to infinity as its density approaches that of the grains. If the particles are buoyant then the initial configuration is stable. An exact time-dependent two-dimensional solution is constructed for plug-flow, which exploits the uncoupling of material columns of grains in the absence of shear. This yields insight into the nature of more complex numerical solutions for strong shear, which are computed with a high resolution, shock-capturing numerical scheme.

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Erosion, transport and segregation of pumice and lithic clasts in pyroclastic flows inferred from ignimbrite at Lascar Volcano, Chile

Cited by 143 publications

References 41 publications

Debris flows: Experiments and modelling

Debris flows: Experiments and modelling

Rounding of pumice clasts during transport: field measurements and laboratory studies

A three-phase mixture theory for particle size segregation in shallow granular free-surface flows

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