Excitation of thermoconvective waves in the continental lithosphere

Birger, B. I.

doi:10.1046/j.1365-246x.2000.00992.x

Cited by 10 publications

(7 citation statements)

References 13 publications

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“…For T s = 100 and T m = 260 K, D true /D cr ~ 1.17. Finally, we note that although it is beyond the scope of this chapter, it is possible that the microphysical processes that accommodate the first ~10% strain during the onset of convection are entirely different than those that govern welldeveloped convection (see, e.g., Birger, 1998Birger, , 2000. Measurements of ice behavior during transient or primary creep (Glen, 1955) may be relevant to the question of the onset of convection in addition to flow laws for steady-state creep (Solomatov and Barr, 2007).…”

Section: Is Convection Possible?mentioning

confidence: 99%

Heat Transfer in Europa’s Icy Shell

Barr¹,

Showman²

Europa

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Heat transport across Europa's ice shell controls the thermal evolution of its interior and provides a source of energy to drive resurfacing. Recent improvements in knowledge of ice rheology, the behavior of convection, and the interaction between convection and lithospheric deformation have led to more realistic and complex models of the geodynamics of Europa's icy shell. The possibility of convection complicates efforts to determine the shell thickness because a thin conductive shell can carry the same heat flux as a thick convective shell. Whether convection occurs depends on ice viscosity, which in turn depends on grain size. The grain size may be controlled by internal deformation, or by impurities, depending on shell composition. Creating the observed surface features with steady-state thermal convection is challenging, even with tidal heating, because the near-surface ice is cold and stiff. Convection models that include surface weakening and compositional buoyancy show promise in explaining some chaos terrains, pits, and uplifts, but new spacecraft and laboratory data and geophysical techniques are needed to match theory to observation.

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Section: Is Convection Possible?mentioning

confidence: 99%

Heat Transfer in Europa’s Icy Shell

Barr¹,

Showman²

Europa

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“…The Andrade parameter averaged over depth of the lithosphere is estimated as A ≈ 10 12 Pa s 1/. 3 (Birger 2004). Such an evaluation of the rheological parameter leads to Ra A ≈ 80 and, consequently, the stagnant lithosphere is unstable.…”

Section: N S Ta B I L I T Y O F T H E S Ta G N a N T L I T H O S P mentioning

confidence: 99%

“…A further increase of the number Ra A leads to a decrease of the imaginary part of increment, which reaches zero at Ra A ≈ 30, and to an increase of its real part. The Andrade parameter averaged over depth of the lithosphere is estimated as (Birger 2004). Such an evaluation of the rheological parameter leads to Ra A ≈ 80 and, consequently, the stagnant lithosphere is unstable.…”

Section: Instability Of the Stagnant Lithosphere: Andrade Rheologymentioning

confidence: 99%

Transient creep and convective instability of the lithosphere

Birger

2012

Geophysical Journal International

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SUMMARY Laboratory experiments with rock samples show that transient creep, at which strain grows with time and strain rate decrease at constant stress, occurs while creep strains are sufficiently small. The transient creep at high temperatures is described by the Andrade rheological model. Since plate tectonics allows only small deformations in lithospheric plates, creep of the lithosphere plates is transient whereas steady‐state creep, described by non‐Newtonian power‐law rheological model, takes place in the underlying mantle. At the transient creep, the effective viscosity, found in the study of postglacial flows, differs significantly from the effective viscosity, which characterizes convective flow, since timescales of these flows are very different. Besides, the transient creep changes the elastic crust thickness estimated within the power‐law rheology of the lithosphere. Two problems of convective stability for the lithosphere with the Andrade rheology are solved. The solution of the first problem shows that the state, in which large‐scale convective flow in the mantle occurs under lithospheric plates, is unstable and must bifurcate into another more stable state at which the lithospheric plates become mobile and plunge into the mantle at subduction zones. If the lithosphere had the power‐law fluid rheology, the effective viscosity of the stagnant lithospheric plates would be extremely high and the state, in which large‐scale convection occurs under the stagnant plates, would be stable that contradicts plate tectonics. The mantle convection forms mobile lithospheric plates if the effective viscosity of the plate is not too much higher than the effective viscosity of the underlying mantle. The Andrade rheology lowers the plate effective viscosity corresponding to the power‐law fluid rheology and, thus, leads to instability of the state in which the plates are stagnant. The solution of the second stability problem shows that the state, in which the lithospheric plate moves as a whole with constant velocity, is stable but small‐amplitude oscillations are imposed on this motion in regions of thickened lithosphere beneath continental cratons (subcratonic roots) where the thickness of the lithosphere is about 200 km. These oscillations create small‐scale convective cells (the horizontal dimensions of the cells are of the order of the subcratonic lithosphere thickness). Direction of motion within the cells periodically changes (the period of oscillations is of the order of 108 yr). The small‐amplitude convective oscillations cause small strains and do not destroy the thickening of the lithosphere beneath cratons. Thus, the transient creep of the lithosphere explains not only mobility of the lithospheric plates but longevity of subcratonic roots as well.

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“…Low amplitude thermoconvective oscillations of the cra tonic lithosphere cause oscillatory movements of the Earth's surface. Taking into account the significant difference between the rate of sedimentation and ero sion, the lithosphere thermoconvective oscillations can be considered as a mechanism for the formation and evolution of sedimentary basins on continental cratons (Birger, 1998;2004).…”

Section: Lithosphere and Mantle Rheologymentioning

confidence: 99%

Transient creep of the lithosphere and its role in geodynamics

Birger

2012

Izv., Phys. Solid Earth

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Laboratory experiments with samples of rocks show that at small strains there is transient creep, at which the strain grows with time, and the strain rate decreases. Plate tectonics allows only small strains in the lithospheric plates, so that the lithosphere creep is transient. In geodynamics, the lithosphere is regarded as a cold boundary layer formed by mantle convection. If we assume that the lithosphere has a steady state creep, which is described by power law non Newtonian rheological model, the low effective viscosity of the lower layers of the lithosphere, obtained by data on small scale postglacial flows, is possible only at high strain rates in these layers. However, the high strain rates in the lithosphere induce large strains that contradict plate tectonics. Transient creep of the lithosphere leads to its mobility at small strains, removing the discrepancy between thermal convection in the mantle and plate tectonics, which holds in the case of power law rheolog ical model of the lithosphere.

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Excitation of thermoconvective waves in the continental lithosphere

Cited by 10 publications

References 13 publications

Heat Transfer in Europa’s Icy Shell

Heat Transfer in Europa’s Icy Shell

Transient creep and convective instability of the lithosphere

Transient creep of the lithosphere and its role in geodynamics

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