Modeling the effect of layered volcanic material on magma reservoir failure and associated deformation, with application to Long Valley caldera, California

Long, S. M.; Grosfils, E. B.

doi:10.1016/j.jvolgeores.2009.05.021

Cited by 28 publications

(26 citation statements)

References 39 publications

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“…A number of complementary analyses are open for the future, by associating our elasto‐plastic and hydromechanical approach with numerous and already well identified other factors. Non‐circular magma chamber geometries (i.e., ellipsoïdal), multiple chambers, elastic heterogeneity and a volcanic edifice [i.e., Pinel and Jaupart , 2003; Gudmundsson , 2006; Masterlark , 2007; Segall , 2009; Long and Grosfils , 2009] are necessary to account for in order to proceed to proper comparison with natural three‐dimensional cases. Incorporation of more realistic rheologies including temperature‐dependent viscosity [e.g., Dragoni and Magnanensi , 1989; Bonaccorso et al , 2005; Karlstrom et al , 2010] and lithospheric flexure [ Galgana et al , 2011] introduces additional controls on failure mechanisms.…”

Section: Discussionmentioning

confidence: 99%

“…Elastic deformation and failure resulting from an inflating magma chamber have been among the first analytical developments applied to geological observations [ Anderson , 1936]. While a variety of magma sources shapes are considered when studying deformation associated to volcanism (e.g., see review by Segall [2009]), the heterogeneity of the medium, densities, thermal and viscous properties are also well‐known first order factors [e.g., Tait et al , 1989; Dragoni and Magnanensi , 1989; Parfitt et al , 1993; Sartoris et al , 1990; Trasatti et al , 2005; Gudmundsson , 2006; Masterlark , 2007; Bonafede and Ferrari , 2009; Long and Grosfils , 2009; Karlstrom et al , 2010]. However, a first reference approach consists in considering an idealized circular or spherical cavity, submitted to uniform internal pressure in a homogeneous isotropic elastic half‐space.…”

Section: Introductionmentioning

confidence: 99%

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Elasto‐plastic and hydromechanical models of failure around an infinitely long magma chamber

Gerbault¹,

Cappa²,

Hassani³

2012

Geochem Geophys Geosyst

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[1] Surface displacements solutions of elastic deformation around an inflating magma chamber generally assume that the associated internal overpressure is limited by the bedrock tensile strength. When considering stress equilibrium in the bedrock adjacent to a spherical or infinitely long cylinder, the gravity body force actually resists tensile failure, thus leading to a much larger pressure threshold. And when considering a Coulomb failure criterion, analytical and numerical models predict that shear failure develops instead of tensile failure. Here, three numerical codes are used to compare elasto-plastic solutions of surface displacements and patterns of failure in plane-strain. Shear failure propagates independently from the surface downward, then from the chamber walls upwards, and finally the two plasticized domains connect. Another test with internal underpressure (simulating source deflation) fits standard solutions from tunneling engineering. The effect of pore fluid pressures is also explored. In case of lithostatic fluid pore pressure in the bedrock, the gravity effect cancels out, and tensile failure is enabled for an overpressure close to the tensile strength. Coupled hydromechanical models in undrained conditions indicate that the initial bedrock porosity modifies the evolution of fluid pressure, volumetric strain and effective normal stress, and consequently also the pressure threshold for the onset of failure. We show that a bedrock of low porosity is more prone to fail than a bedrock of high porosity. In summary, our elasto-plastic and hydromechanical models illustrate the contexts for either tensile or shear failure around magmatic bodies, at the same time complementing and delimiting predictions deduced from elasticity.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Elasto‐plastic and hydromechanical models of failure around an infinitely long magma chamber

Gerbault¹,

Cappa²,

Hassani³

2012

Geochem Geophys Geosyst

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“…The physics of magma ascent in dikes has been the subject of numerous studies [e.g., Lister and Kerr , ; Rubin , ; Gudmundsson , , ; Ito and Martel , ]. Others have considered magma chamber pressurization beneath small (relative to Venus volcanoes) volcanic edifices and the orientations of intrusions emanating from them [e.g., Pinel and Jaupart , , ; Grosfils , ; Long and Grosfils , ; Hurwitz et al ., ]. However, none of these studies explicitly addressed flexural stress states, which can provide stress magnitudes well in excess of those from simple compression of the substratum and significantly different distributions of stress with depth.…”

Section: Introductionmentioning

confidence: 99%

The influence of lithospheric flexure on magma ascent at large volcanoes on Venus

2013

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[1] Large volcanoes on Venus exert large vertical loads on the lithosphere, which responds by deflecting downward. Stresses induced by this lithospheric flexure can have a strong influence on magma ascent pathways from the mantle source region to the surface. Here we propose that flexural stresses exert control over the shapes of volcanic edifices on Venus, applying criteria for magma ascent expressed in terms of stress orientations (can vertical dikes form?) and gradients (is magma squeezed upward or downward in a vertical dike?) to determine favored magma ascent paths and locations. For conical edifices emplaced on lithosphere with high elastic thickness T e , (e.g., > 40 km) both sets of magma ascent criteria are satisfied over the entire lithosphere, allowing essentially unimpeded ascent of magma to the surface and the formation of relatively steep edifices. However, for lower values of T e , high adverse stress gradients tend to cut off magma ascent beneath the summit, instead favoring lateral transport of magma at depth to distal regions with gentler stress gradients, resulting in domical edifice shapes. At the lowest values of T e (< 10 km), large short-wavelength deflections of the lithosphere tend to produce narrow and widely spaced zones of magma ascent: Such zones may produce annular ridges of volcanic material, thereby generating forms characteristic of a subset of features known as "coronae" on Venus. Another subset of coronae may form by intrusive-based generation of annular fractures at the edge of the summit region of domical edifices, as proposed for Alba Mons on Mars.

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“…Analytic models of inflating magma sources with simple point sources to spherical and ellipsoidal magma chambers embedded within an elastic half‐space [i.e., Mogi , 1958; Davis , 1986; McTigue , 1987] have been used to study surface deformation in volcanic areas. Elaborate numerical models that incorporate contributing tectonic sources, topographic loading, and/or lithospheric layers of different material properties have been used to predict stress orientations near volcanic centers [e.g., McGovern and Solomon , 1998; McGovern et al , 2001; Cailleau et al , 2005; Manconi et al , 2007; Long and Grosfils , 2009]. Authors have also explored the stability of magma chambers due to pressurization [e.g., Sartoris et al , 1990; Parfitt et al , 1993] and volcanic edifice loading [e.g., Russo et al , 1997; Pinel and Jaupart , 2003].…”

Section: Introductionmentioning

confidence: 99%

“…Authors have also explored the stability of magma chambers due to pressurization [e.g., Sartoris et al , 1990; Parfitt et al , 1993] and volcanic edifice loading [e.g., Russo et al , 1997; Pinel and Jaupart , 2003]. However, recent numerical modeling approaches that incorporate gravitational loading and lithostatic prestress conditions predict significantly different patterns of maximum stresses and strains [e.g., Grosfils , 2007; Hurwitz et al , 2009; Long and Grosfils , 2009] compared to earlier efforts. Host rock materials in these recent models incorporate compressional stresses that increase in all three spatial directions as a function of lithospheric depth, rather than limiting treatment of the host rock stress to the component acting normal to the reservoir wall.…”

Section: Introductionmentioning

confidence: 99%

Evolution of large Venusian volcanoes: Insights from coupled models of lithospheric flexure and magma reservoir pressurization

Galgana¹,

McGovern²,

Grosfils³

2011

J. Geophys. Res.

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[1] The growth and evolution of large volcanic edifices on Venus should reflect interactions between local magma reservoir-induced stresses and broader-scale stresses resulting from flexure of the lithosphere beneath the edifice load. Here, we explore the relationship between magma movement in the lithosphere and the flexural stress state via static, gravitationally loaded, axisymmetric finite element models. We find that reservoirs situated in the lower (extensional) lithosphere fail at the bottom and are therefore not viable long-term conduits for upward magma transport. Furthermore, for high-stress conditions (e.g., large edifices or thin lithospheres), chambers in the lowermost lithosphere exceed the failure criterion even before pressurization and are therefore unstable. In contrast, magma chambers located in the upper (compressional) lithosphere fail at or somewhat above the reservoir midsection, promoting lateral sill injection; continued failure in this mode would tend to produce oblate magma chambers with zones of intrusion at their margins. Reservoirs near the flexural neutral plane require the greatest overpressure to reach failure, emplacing cone sheets that transition to sills further from the chamber. The out-of-plane orientation of principal extensional stresses in the flexed lower lithosphere predicts the presence of radial dikes that are likely the main conduits for any subsequent magma ascent from the mantle melt source region. Our results also explain how the evolving stress state in the lithosphere tends to redirect magma passage over time: magma ascending into the lithosphere beneath the edifice is diverted to lateral sills in the upper lithosphere, inhibiting summit eruptions and possibly shifting eruption locations to the lower flanks at and beyond the distal margins of an oblate chamber or sill complex. We apply these results to interpret the observed structure and tectonism of Sapas Mons, Venus, in terms of flexurally controlled intrusive processes.Citation: Galgana, G. A., P. J. McGovern, and E. B. Grosfils (2011), Evolution of large Venusian volcanoes: Insights from coupled models of lithospheric flexure and magma reservoir pressurization,

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Modeling the effect of layered volcanic material on magma reservoir failure and associated deformation, with application to Long Valley caldera, California

Cited by 28 publications

References 39 publications

Elasto‐plastic and hydromechanical models of failure around an infinitely long magma chamber

Elasto‐plastic and hydromechanical models of failure around an infinitely long magma chamber

The influence of lithospheric flexure on magma ascent at large volcanoes on Venus

Evolution of large Venusian volcanoes: Insights from coupled models of lithospheric flexure and magma reservoir pressurization

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