Repeated fracture and healing of silicic magma generate flow banding and earthquakes?

Tuffen, Hugh; Dingwell, Donald B.; Pinkerton, Harry

doi:10.1130/g19777.1

Cited by 340 publications

(306 citation statements)

References 33 publications

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“…Webb and Dingwell [1990a, p. 125] wrote that "although the breakage is unrelated to the observation of non-Newtonian viscosity, their close proximity in this and earlier studies suggests that brittle failure of igneous melts, may, in general, be preceded by a period of non-Newtonian rheology. " Tuffen et al [2003" Tuffen et al [ , p. 1090 stated that "analysis of equations 2 and 3 (Maxwell model with a constant viscosity) shows that fracture will only occur if viscous shear stress exceeds a critical value, which demonstrates that fracture is not an inevitable consequence of non-Newtonian deformation-an assumption implicit in existing models of strain induced fracture [Goto, 1999;Papale, 1999]." Finally, Simmons [1998, p. 6] wrote, "the major findings of this work include the observation of shear thinning, …, and the discovery that the maximum sustainable stress has a limit at high deformation rates ….…”

Section: Introductionmentioning

confidence: 99%

Brittleness of fracture in flowing magma

Ichihara

Rubin

2010

J. Geophys. Res.

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[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.

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Section: Introductionmentioning

confidence: 99%

Brittleness of fracture in flowing magma

Ichihara

Rubin

2010

J. Geophys. Res.

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“…As the lava continued to advance downslope, individual flow units advanced and overlapped, forming flow ramps (Cas and Wright 1987;Gottsmann and Dingwell 2001). Continual extrusion, repetitive cycles of breaking, flowing and healing (Tuffen et al 2003;Tuffen and Dingwell 2005;Vasseur et al 2013;Cabrera et al 2015) and progressive deformation produced a third generation of largest scale folding. Small-scale folds were superimposed upon the younger medium-to large-scale folding (Fig.…”

Section: Progressive Deformationmentioning

confidence: 99%

Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

2018

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The Rocche Rosse lava flow marks the most recent rhyolitic extrusion on Lipari island (Italy), and preserves evidence for a multi-stage emplacement history. Due to the viscous nature of the advancing lava (10 8 to 10 10 Pa s), indicators of complex emplacement processes are preserved in the final flow. This study focuses on structural mapping of the flow to highlight the interplay of cooling, crust formation and underlying slope in the development of rhyolitic lavas. The flow is made up of two prominent lobes, small (< 0.2 m) to large (> 0.2 m) scale folding and a channelled geometry. Foliations dip at 2-4°over the flatter topography close to the vent, and up to 30-50°over steeper mid-flow topography. Brittle faults, tension gashes and conjugate fractures are also evident across flow. Heterogeneous deformation is evident through increasing fold asymmetry from the vent due to downflow cooling and stagnation. A steeper underlying topography mid-flow led to development of a channelled morphology, and compression at topographic breaks resulted in fold superimposition in the channel. We propose an emplacement history that involved the evolution through five stages, each associated with the following flow regimes: (1) initial extrusion, crustal development and small scale folding; (2) extensional strain, stretching lineations and channel development over steeper topography; (3) compression at topographic break, autobrecciation, lobe development and medium scale folding; (4) progressive deformation with stagnation, large-scale folding and refolding; and (5) brittle deformation following flow termination. The complex array of structural elements observed within the Rocche Rosse lava flow facilitates comparisons to be made with actively deforming rhyolitic lava flows at the Chilean volcanoes of Chaitén and Cordón Caulle, offering a fluid dynamic and structural framework within which to evaluate our data.

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“…The threshold criterion used is either a given overpressure within the magma below the plug [Lensky et al, 2008] or the condition for brittle failure of the magma [Collier and Neuberg, 2006]. The onset of brittle failure has been identified to occur when the product of the melt viscosity and the shear strain rate is larger than the shear strength of the melt (s s ) [Webb and Dingwell, 1990], values being estimated between 10 7 and 10 8 Pa for pure glass [Tuffen et al, 2003;Tuffen and Dingwell, 2005].…”

Section: Origin Of Cyclic Deformationmentioning

confidence: 99%

Conditions for detection of ground deformation induced by conduit flow and evolution

et al. 2011

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[1] At mature andesitic volcanoes, magma can reach the surface through the same path for several eruptions thus forming a volcanic conduit. Because of degassing, cooling, and crystallization, magma viscosity increase in the upper part of the conduit may induce the formation of a viscous plug. We conducted numerical simulations to quantify the deformation field caused by this plug emplacement and evolution. Stress continuity between Newtonian magma flow and elastic crust is considered. Plug emplacement causes a ground inflation correlated to a decrease of the magma discharge rate. A parametric study shows that surface displacements depend on three dimensionless numbers: the conduit aspect ratio (radius/length), the length ratio between the plug and the conduit, and the viscosity contrast between the plug and the magma column. Larger displacements are obtained for high-viscosity plugs emplaced in large aspect ratio conduits. We find that only tiltmeters or GPS located close to the vent (a few hundred meters) might record the plug emplacement. At immediate proximity of the vent, plug emplacement might even dominate the deformation signal over dome growth or magma reservoir pressurization effects. For given plug thicknesses and viscosity profiles, our model explains well the amplitude of tilt variations (from 1 to 25 mrad) measured at Montserrat and Mt. St. Helens. We also demonstrate that at Montserrat, even if most of the tilt signal is due to shear stress induced by magma flow, pressurization beneath the plug accounts for 20% of the signal.

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Repeated fracture and healing of silicic magma generate flow banding and earthquakes?

Cited by 340 publications

References 33 publications

Brittleness of fracture in flowing magma

Brittleness of fracture in flowing magma

Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

Conditions for detection of ground deformation induced by conduit flow and evolution

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