Role of conduit shear on ascent of the crystal-rich magma feeding the 800-year-b.p. Plinian eruption of Quilotoa Volcano (Ecuador)

Rosi, Mauro; Landi, Patrizia; Polacci, Margherita; Muro, Andréa Di; Zandomeneghi, D.

doi:10.1007/s00445-003-0312-z

Cited by 64 publications

(7 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Hence, brittle shear deformation is unlikely to occur. However, note that pumice textures thought to have formed as a consequence of shear heating and localization may bear evidence for brittle deformation during explosive eruptions … [Polacci et al, 2005;Rosi et al, 2004]. "…”

Section: Introductionmentioning

confidence: 99%

Brittleness of fracture in flowing magma

Ichihara

Rubin

2010

J. Geophys. Res.

View full text Add to dashboard Cite

[1] Understanding the transition to brittle fracture of flowing magma is essential for estimating the explosiveness of a volcanic eruption. In order to quantify brittleness of flowing magma, a new parameter b is introduced, which is a function of the ratio of the rate of change of the strain energy due to elastic distortional deformation to the mechanical power due to total distortional deformation rate. From the perspective of b, dependence of brittle fracture of magma on stress, decompression rate, strain rate, and shear-thinning effects are reviewed. The experimental data of Kameda et al. (2008) for rapid decompression of simulants of bubbly magma have also been reexamined. The results show that b exhibits a strong transition that correlates well with the observed transition between ductile expansion to brittle fragmentation. Moreover, b is useful in considering the effects of shear-thinning and steady-creep conditions on brittle fracture. Statements in the literature that suggest that materials behave in a brittle manner at sufficiently high strain rate are correct. However, these statements do not precisely quantify the notion of high strain rate so they are easy to misinterpret when considering the effect of shear thinning. Although shear thinning tends to increase the absolute magnitude of the total strain rate, it does not necessarily increase brittleness. Also, in principle, it is unlikely for brittle fracture to occur at steady creep. Cracking observed in steady-creep experiments of magma (Lavallee et al., 2007 may be attributed to small fluctuations with sufficiently high frequencies to satisfy the conditions for brittle fracture.

show abstract

Section: Introductionmentioning

confidence: 99%

Brittleness of fracture in flowing magma

Ichihara

Rubin

2010

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…Manga 1999; Polacci et al 2003;Rust et al 2003;Rosi et al 2004;Mueller et al 2005;Gualda and Rivers 2006;Wright et al 2006;Bernard et al 2007; Bouvet de Maisonneuve et al 2008).…”

unclassified

“…The KPT pumices display macroscopic textures ranging from tubular (i.e., tube pumice) to near-spherical (i.e., frothy pumice) networks of bubbles, suggesting that the magmatic foam in different parts of the conduit was exposed to variable strain (Marti et al 1999;Polacci et al 2003;Rosi et al 2004;Wright et al 2006) during ascent. A previous study on the KPT eruption (Bouvet de Maisonneuve et al 2008) reported highly variable permeabilities (variations over several orders of magnitude) of tube and frothy pumices for given porosities, implying that parameters other than porosity exerts a strong control on magma outgassing.…”

mentioning

confidence: 99%

Controls on magma permeability in the volcanic conduit during the climactic phase of the Kos Plateau Tuff eruption (Aegean Arc)

Degruyter

Burgisser

2009

Bull Volcanol

View full text Add to dashboard Cite

X-ray computed microtomography (µCT) was applied to pumices from the largest Quaternary explosive eruption of the active South Aegean Arc (the Kos Plateau Tuff; KPT) in order to better understand magma permeability within volcanic conduits. Two different types of pumices (one with highly elongated bubbles, tube pumice; and the other with near spherical bubbles, frothy pumice) produced synchronously and with identical chemical composition were selected for µCT imaging to obtain porosity, tortuosity, bubble size and throat size distributions. Tortuosity drops on average from 2.2 in frothy pumice to 1.5 in tube pumice. Bubble size and throat size distributions provide estimates for mean bubble size (~93-98 μm) and mean throat size (~23-29 μm). Using a modified Kozeny-Carman equation, variations in porosity, tortuosity, and throat size observed in KPT pumices explain the spread found in laboratory measurements of the Darcian permeability. Measured difference in inertial permeability between tube and frothy pumices can also be partly explained by the same variables but require an additional parameter related to the internal roughness of the porous medium (friction factor f 0 ). Constitutive equations for both types of permeability allow the quantification of laminar and turbulent gas escape during ascent of rhyolitic magma in volcanic conduits.

show abstract

“…Conversion to volumetric vesicle number densities can easily be obtained dividing the areal number densities by the average vesicle diameter. These values were then compared with measurements made on the Campanian Ignimbrite pyroclasts (Polacci et al, 2003) and on pumice clasts from calc-alkaline eruptions from subduction volcanoes (Klug and Cashman 1994;Polacci et al 2001;Klug et al, 2002;Rosi et al, 2004).…”

Section: Methodsmentioning

confidence: 99%

“…If pumice clasts do not exhibit evidence of postfragmentation expansion features, vesicularities can be assumed to represent the state of magma at the time of fragmentation, and differences in vesicularities may therefore record different fragmentation conditions owing to the different magma properties characterizing alkaline and calc-alkaline compositions. Rosi et al (2004); ^ from Klug et al (2002), 0.82 is helium picnometer vesicularity; ^^ from Klug and Cashman (1994), 0.80 and 0.61 are helium picnometer vesicularities.…”

Section: Quantification Of Pumice Texturesmentioning

confidence: 99%

Constraining the dynamics of volcanic eruptions by characterization of pumice textures

Polacci

2009

Annals of Geophysics

View full text Add to dashboard Cite

We have characterized the textures of pumice clasts from Phlegraean Fields to gain insights into the conduit flow-dynamics of alkaline explosive eruptions. Vesicularities, vesicle number densities, and vesicle sizes and shapes were measured to obtain the bulk and groundmass properties of the juvenile fraction of Campanian Ignimbrite (CI) and Agnano Monte Spina (AMS) eruptions. The results report the coexistence of three end-member pumice types in the deposits of both eruptions, 1) microvesicular, 2) tube and 3) expanded, which differ according to clast morphology and the macro-to microscopic vesicle texture. Vesicularities (0.85-0.94 for CI, 0.51-0.91 for AMS) and vesicle number densities (2-4 ×10 5 cm −2 in CI, 3 ×10 5 -10 6 cm −2 in AMS) span quite a wide range in all the three pumice types. Overall, tube pumices exhibit the highest bulk (0.89) and groundmass (CI 0.85, AMS 0.82) average vesicle volume fractions but the lowest average vesicle number densities (CI 2 ×10 5 , AMS 4 ×10 5 cm −2 ). Comparison with textures of calc-alkaline pumices has revealed many similarities and points to a common origin and distribution of the products from both magma compositions within the volcanic conduit. In addition, the results of the textural analysis were interpreted in the light of the conduit flow modeling of Phlegraean Fields eruptions. The comparison of textural observations with results from simulations of conduit magma ascent has exhibited a good agreement between measured and numerically calculated vesicularities for both compositions, helping to constrain the overall dynamics of alkaline versus calc-alkaline eruptions.

show abstract

Role of conduit shear on ascent of the crystal-rich magma feeding the 800-year-b.p. Plinian eruption of Quilotoa Volcano (Ecuador)

Cited by 64 publications

References 33 publications

Brittleness of fracture in flowing magma

Brittleness of fracture in flowing magma

Controls on magma permeability in the volcanic conduit during the climactic phase of the Kos Plateau Tuff eruption (Aegean Arc)

Constraining the dynamics of volcanic eruptions by characterization of pumice textures

Contact Info

Product

Resources

About