Tying textures of breadcrust bombs to their transport regime and cooling history

Benage, M. C.; Dufek, Josef; Degruyter, Wim; Geist, D.; Harpp, K. S.; Rader, Erika

doi:10.1016/j.jvolgeores.2014.02.005

Cited by 27 publications

(31 citation statements)

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“…PDC temperatures can be derived through direct measurement of deposits [e.g., Banks and Hoblitt, 1981;Cole et al, 2002] or through the use of proxies such as thermoremanent magnetization [e.g., Mandeville et al, 1994;Cioni et al, 2004;Roperch et al, 2014;Rader et al, 2015], measuring abundance and reflectance of charcoal [e.g., Scott and Glasspool, 2005;Scott et al, 2008;Pensa et al, 2015], and measuring rind thickness of cauliflower bombs [Benage et al, 2014]. PDC temperatures can be derived through direct measurement of deposits [e.g., Banks and Hoblitt, 1981;Cole et al, 2002] or through the use of proxies such as thermoremanent magnetization [e.g., Mandeville et al, 1994;Cioni et al, 2004;Roperch et al, 2014;Rader et al, 2015], measuring abundance and reflectance of charcoal [e.g., Scott and Glasspool, 2005;Scott et al, 2008;Pensa et al, 2015], and measuring rind thickness of cauliflower bombs [Benage et al, 2014].…”

Section: Introductionmentioning

confidence: 99%

“…The principal mechanism for altering the thermal state of a PDC during transport is entrainment, and hence, proxies for current temperature can provide information about bulk air entrainment. PDC temperatures can be derived through direct measurement of deposits [e.g., Banks and Hoblitt, 1981;Cole et al, 2002] or through the use of proxies such as thermoremanent magnetization [e.g., Mandeville et al, 1994;Cioni et al, 2004;Roperch et al, 2014;Rader et al, 2015], measuring abundance and reflectance of charcoal [e.g., Scott and Glasspool, 2005;Scott et al, 2008;Pensa et al, 2015], and measuring rind thickness of cauliflower bombs [Benage et al, 2014]. Cauliflower bombs have a vesicular interior and a dense exterior rind [Walker, 1969;Wright et al, 2007], and the dissolved water and rind thickness can provide data on the syn-eruptive thermal history [Benage et al, 2014].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Quantifying entrainment in pyroclastic density currents from the Tungurahua eruption, Ecuador: Integrating field proxies with numerical simulations

Benage

Dufek

Mothes

2016

Geophysical Research Letters

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The entrainment of air into pyroclastic density currents (PDCs) impacts the dynamics and thermal history of these highly mobile currents. However, direct measurement of entrainment in PDCs is hampered due to hazardous conditions and opaqueness of these flows. We combine three‐dimensional multiphase Eulerian‐Eulerian‐Lagrangian calculations with proxies of thermal conditions preserved in deposits to quantify air entrainment in PDCs at Tungurahua volcano, Ecuador. We conclude that small‐volume PDCs develop a particle concentration gradient that results in disparate thermal characteristics for the concentrated bed load (>600 to ~800 K) and the overlying dilute suspended load (~300–600 K). The dilute suspended load has effective entrainment coefficients 2–3 times larger than the bed load. This investigation reveals a dichotomy in entrainment and thermal history between two regions in the current and provides a mechanism to interpret the depositional thermal characteristics of small‐volume but frequently occurring PDCs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantifying entrainment in pyroclastic density currents from the Tungurahua eruption, Ecuador: Integrating field proxies with numerical simulations

Benage

Dufek

Mothes

2016

Geophysical Research Letters

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“…The postfragmentation textural changes may be more significant for pyroclasts of less-viscous low-Si compositions, unless it has high crystal content that causes significant rheological stiffening (e.g., Mader et al, 2013;Moitra & Gonnermann, 2015;Sehlke et al, 2014;Spera, 2000;Thomas et al, 1994). Furthermore, coarse lapilli and larger-size clasts tend to quickly form a solid crust due to faster cooling at the surface (Figure 11b), which not only contributes to the formation of breadcrust bombs (e.g., Benage et al, 2014;Giachetti et al, 2010;Wright et al, 2007) but may also inhibit any post-depositional welding with adjacent clasts.…”

Section: Implications For Pre-to Post-eruptive Volcanic Processesmentioning

confidence: 99%

Effects of Size and Temperature‐Dependent Thermal Conductivity on the Cooling of Pyroclasts in Air

Moitra

Sonder

Valentine

2018

Geochem Geophys Geosyst

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The knowledge of the cooling time scales of pyroclasts, in conditions of free to forced convection, is of paramount importance in microtextural analysis, development of welded deposits, and in eruption column and pyroclast flow modeling. We performed cooling experiments of heated rock inside a cylindrical wind tunnel under a range of air speeds. In order to estimate the heat transfer coefficients, we modeled the transient temperature distribution in the sample with temperature‐dependent thermal diffusivity and heat capacity, which were obtained from laser flash measurements. For air speeds up to 15 m/s and for sample temperatures up to 1383 K (1110 ° C), a Nusselt‐Reynolds (Nu‐Re) relationship up to Re=3× 104 is established in this study. We find that the dependency of heat loss on size is particularly important for pyroclasts larger than ∼1 mm. Our results suggest that the cooling time scales of pyroclasts could be large enough to cause postfragmentation modification of clast microtextures. We further show that clasts of few‐centimeter and larger develop solid crusts with molten cores within time scales of a few minutes and therefore may inhibit postdepositional welding.

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“…This eruption triggered the formation of pyroclastic currents that were funneled in ravines of the fluvial drainage network on the steep flanks of the volcano (e.g. Kelfoun et al 2009, Douillet et al 2013a, 2013b, Rader et al 2014, Bernard et al 2014, Benage et al 2014. Cross-laminated sediments forming dune bedforms dominated by ash are preserved as marginal, isolated patches with an extent of several hundreds of meters on the overbanks of the ravines that directed the flows (Douillet et al 2013a(Douillet et al , 2013b.…”

Section: A Dataset Based On the 2006 Eruption Of Tungurahuamentioning

confidence: 99%

Shark-fins: overturned patterns linked to shear instabilities at the flow-bed boundary. Examples from the deposits of the 2006 pyroclastic currents at Tungurahua volcano (Ecuador)

Douillet¹,

Chaffaut²,

Schlunegger³

et al. 2018

Preprint

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SedimentologyShark-fin structures: overturned convolute and flame patterns due to waves at the shear horizon of a flow-bed boundary. Examples from the deposits of the 2006 pyroclastic currents at Tungurahua volcano (Ecuador) AbstractEnigmatic structures are documented in deposits of dilute pyroclastic currents and grouped under the term "shark-fins". They consist of an overturning of a few laminae on a decimeter scale, forming overbent "flames" or convolute laminae, which occur in successive, periodic patterns. More than 200 shark-fins were investigated and measured in the cross-laminated deposits from the 2006 pyroclastic currents of Tungurahua volcano (Ecuador).These shark-fins are interpreted in terms of syndepositional soft sediment deformation pattern whereby waves form at the interface of a shear horizon at the flow-bed boundary and rework the bed. The shark-fins are not related to Kelvin-Helmholtz instabilities. Instead, a theoretical framework based on two layers separated by a shear horizon is developed. The calculated growth rate of the waves is compared to sedimentation rates in order to infer aspects of the stability and preservation of such sheared interfaces. The process-based interpretation is supported by the results from the physical model.Various other incidental patterns are presented and discussed, which likely result from collisions of flows with deposits, intraflow events and syn-flow slumping. We thus identify the necessary key observations for the interpretation of shark-fin structures for different types of triggers. Such observations on flow-bed interactions contribute to the understanding of a flow rheology, shear partitioning, and the transmission of shear stress out of the flow and into the substrate.

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Tying textures of breadcrust bombs to their transport regime and cooling history

Cited by 27 publications

References 55 publications

Quantifying entrainment in pyroclastic density currents from the Tungurahua eruption, Ecuador: Integrating field proxies with numerical simulations

Quantifying entrainment in pyroclastic density currents from the Tungurahua eruption, Ecuador: Integrating field proxies with numerical simulations

Effects of Size and Temperature‐Dependent Thermal Conductivity on the Cooling of Pyroclasts in Air

Shark-fins: overturned patterns linked to shear instabilities at the flow-bed boundary. Examples from the deposits of the 2006 pyroclastic currents at Tungurahua volcano (Ecuador)

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