Transition between fragmentation and permeable outgassing of low viscosity magmas

Namiki, Atsuko; Manga, Michael

doi:10.1016/j.jvolgeores.2007.07.020

Cited by 134 publications

(110 citation statements)

References 43 publications

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“…For the Hawaiian eruption, there are no feasible solutions that would predict brittle magma fragmentation. This is consistent with the view of hydrodynamical fragmentation during these eruptions (e.g., Namiki and Manga 2008;Houghton and Gonnermann 2008). Accordingly, we model bubbly flow up to the surface (Parfitt 2004), assuming an exit pressure of 10 5 Pa at the vent.…”

Section: Magma Ascent Modelingsupporting

confidence: 86%

“…This is also the case for the basaltic Plinian eruptions. In contrast, for the Hawaiian and Strombolian eruptions, our model results indicate that Ca 1, with insufficient overpressure for brittle fragmentation, thus consistent with the work of Namiki and Manga (2008). Although our model results imply that bubble shapes for the Hawaiian and Strombolian eruptions should have had values of ≈ 1 during magma ascent within the conduit, this cannot be established unequivocally because of post-fragmentation shape relaxation.…”

Section: Resultssupporting

confidence: 56%

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Relating vesicle shapes in pyroclasts to eruption styles

et al. 2013

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Vesicles in pyroclasts provide a direct record of conduit conditions during explosive volcanic eruptions. Although their numbers and sizes are used routinely to infer aspects of eruption dynamics, vesicle shape remains an underutilized parameter. We have quantified vesicle shapes in pyroclasts from fall deposits of seven explosive eruptions of different styles, using the dimensionless shape factor , a measure of the degree of complexity of the bounding surface of an object. For each of the seven eruptions, we have also estimated the capillary number, Ca, from the magma expansion velocity through coupled diffusive bubble growth and conduit flow modeling. We find that is smaller for eruptions with Ca 1 than for eruptions with Ca 1. Consistent with previous studies, we interpret these results as an expression of the relative importance of structural changes during magma decompression and bubble growth, such as coalescence and shape relaxation of bubbles by capillary stresses. Among the samples analyzed, Strombolian and Hawaiian fire-fountain eruptions have Ca 1, in contrast to Vulcanian, Plinian, and ultraplinian eruptions. Interestingly, the basaltic Plinian eruptions of Tarawera volcano, New Zealand in 1886 and Mt. Etna, Italy in 122 BC, for which the cause of intense explosive activity has

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Section: Magma Ascent Modelingsupporting

confidence: 86%

Section: Resultssupporting

confidence: 56%

Relating vesicle shapes in pyroclasts to eruption styles

et al. 2013

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“…The measured radial growth rates of approximately 1-10 µm s − 1 and strain rate of 0.1 s − 1 are orders of magnitude too slow to cross the glass transition and cause fragmentation 26 . And, the rates of bubble growth and expansion, 2×10 − 4 m s − 1 , are not rapid enough to cross the inertia-driven fragmentation threshold proposed for low-viscosity basaltic melts 27 . The experiments indicate that initial BNDs are similar to those seen for basaltic, Plinian eruptions and suggest the possibility that all vesiculating basaltic magmas with moderate water concentrations can potentially form Plinian eruptions because of the observed correlations between BND and explosivity 4,19 .…”

Section: Discussionmentioning

confidence: 98%

A four-dimensional X-ray tomographic microscopy study of bubble growth in basaltic foam

et al. 2012

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understanding the influence of bubble foams on magma permeability and strength is critical to investigations of volcanic eruption mechanisms. Increasing foam porosity decreases strength, enhancing the probability of an eruption. However, higher porosities lead to larger permeabilities, which can lessen the eruption hazard. Here we measure bubble size and wall thickness distributions, as well as connectivity, and calculate permeabilities and tensile strengths of basaltic foams imaged by synchrotron X-ray tomographic microscopy during bubble growth in hydrated basaltic melts. Rapid vesiculation produces porous foams whose fragmentation thresholds are only 9-10 mPa and whose permeabilities increase from approximately 1×10 − 10 to 1×10 − 9 m 2 between 10 and 14 s despite decreasing connectivity between bubbles. These results indicate that basaltic magmas are most susceptible to failure immediately upon vesiculation and at later times, perhaps only 10's of seconds later, permeability increases may lessen the hazard of explosive, basaltic, Plinian eruptions.

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“…For example, how can recording of acoustic emissions during laboratory deformation of samples be used as analog of seismicity in natural systems? Experiments on simplified analog systems are also needed to separate otherwise intricate effects, test hypotheses and define the important parameters of a process [Namiki and Manga, 2008, Namiki et al 2014, Namiki et al 2016, Spina et al 2016a. For instance, large-scale analog experiments can unveil complexities in the conduit of maar-diatreme volcanoes [Valentine et al 2012, Taddeucci et al 2013.…”

Section: Methodsmentioning

confidence: 99%