Surface deformation, gravity and the geoid from a three-dimensional convection model at low Rayleigh numbers

Craig, Claire Harvey; McKenzie, Dan

doi:10.1016/0012-821x(87)90056-2

Cited by 13 publications

(11 citation statements)

References 11 publications

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“…This is similar to radii of the heat flow and seismic velocity anomalies around Yellowstone, and consistent with numerical plume simulations (e.g. Craig & McKenzie 1987). For x, to be positive in the + y quadrant when greater than -150 km from Yellowstone where av,/dy is likely to be positive (v, is upward and hence negative beneath Yellowstone, and its absolute value will be likely to decrease away from the centre of the upwelling; hence both dv,/ay and av,/ax are likely to be positive moving in the +x and +y directions away from Yellowstone) (equation 2.6), Jv,,/az must be sufficiently large and positive to overwhelm Jv,/dy, suggesting that vy increases strongly with depth.…”

Section: Three-dimensional Modelsupporting

confidence: 90%

“…Both gravity and geoid anomalies have the magnitude and sign expected from numerical simulations of upwelling mantle plumes (e.g. McKenzie et Craig & McKenzie 1987), suggesting that one is present beneath Yellowstone.…”

supporting

confidence: 53%

“…However, no analytic models exist for sheared plumes, and flow within the mantle is likely to be sufficiently vigorous that, given the limitations of the present generation of supercomputers (e.g. Craig & McKenzie 1987), attainable three-dimensional numerical dynamic models from first principles are unlikely to model it well. Modelling the dynamics of such a plume and its interaction with its surroundings properly is thus not yet possible.…”

mentioning

confidence: 99%

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Deformation of the NE Basin and Range Province: the response of the lithosphere to the Yellowstone plume?

Westaway

1989

Geophysical Journal International

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SUMMARY Tectonic deformation in the NE Basin and Range Province of the western United States is concentrated in two zones, the N‐S trending northern part of the Intermountain seismic belt in northern Utah, SE Idaho and SW Wyoming and the E‐W trending Central Idaho seismic zone, which converge at Yellowstone in NW Wyoming. Accepting the popular view that the Yellowstone volcanic field is above an upwelling plume from the deep mantle, I explore the possibility that deformation of the brittle upper crust in these two seismic zones may be caused by return flow from this plume. This return flow is assumed sheared SW in the direction of motion of the North American plate relative to Yellowstone. The Snake River Plain (SRP), a linear outcrop of Neogene and Quaternary basalt that trends SW from Yellowstone for more than 400 km, bisecting the angle between the two seismic zones, may be a trail formed as the plate moves SW across the upwelling plume. Beyond ∼150 km from Yellowstone, slip vectors on active normal faults in both deforming zones are oriented inwards at ∼45° towards the SW azimuth along the SRP. Normal Slip rates on these faults are typically 1 mm yr−1, implying extensional strain rate ∼10−15 S−1. Proportions of normal slip and strike slip suggest faults in the Intermountain seismic belt are rotating anticlockwise at ∼2° Myr−1 around vertical axes, and faults in the central Idaho seismic zone are rotating clockwise at similar rates. Within ∼100 km of Yellowstone, observed sense of rotation around vertical axes in both zones appears reversed. Tilt rates of hanging wall beds suggest most faults in both zones are rotating at ∼2° Myr−1 (also ∼10−15 S−1) around horizontal axes oriented NW. The relative size of rotation rate around vertical axes and horizontal extensional strain rate is shown to imply that velocity in the underlying deforming ‘fluid’ is small in the direction perpendicular to the axis of the SRP. In an initial model, this velocity is set to zero, enabling the two‐dimensional pattern of flow at the horizontal upper boundary of this deforming fluid to be solved straightforwardly. This approximation enables observed rates and senses of horizontal extension and rotation around a vertical axis to be explained as consequences of the pattern of horizontal gradients of velocity parallel to the axis of the SRP in the deforming fluid beneath the brittle layer. A refinement suggests that velocity perpendicular to the SRP near the upper boundary of the deforming ‘fluid’ is small but inward towards the SRP from both sides, and is accompanied by downwelling beneath the SRP beyond ∼100 km SW of Yellowstone. This pattern of flow will act to move magma in the uppermost mantle beneath the SRP from its sides. It may thus reconcile petrological observations that SRP basalts do not show deep mantle characteristics expected had they been extruded from the Yellowstone plume, with the existence of this plume nearby. Conservation of angular momentum around horizontal axes perpendicular to the SRP for the combined system of ...

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Section: Three-dimensional Modelsupporting

confidence: 90%

supporting

confidence: 53%

mentioning

confidence: 99%

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Deformation of the NE Basin and Range Province: the response of the lithosphere to the Yellowstone plume?

Westaway

1989

Geophysical Journal International

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“…The orthogonal hot and cold sheets are similar to the spokes described by Whitehead & Parsons (1978) in high Rayleigh number convection heated from below. They are also evident in the numerical experiments of Craig & McKenzie (1987) where a relatively low Rayleigh number permitted a regular grid-like distribution of hot and cold sheets. Figure 2 shows contour line drawings in Cartesian projection of the thermal anomalies at six horizontal levels (including the same levels as Fig.…”

Section: Thermal Structuresmentioning

confidence: 80%

“…Flow impinging on a horizontal boundary exerts a normal stress on that boundary which must be matched by an external load in order for the condition of zero normal velocity to be met on the boundary (McKenzie 1977;Parsons & Daly 1983;Lin & Parmentier 1985;Craig & McKenzie 1987). For convection in the mantle this external load may be provided by variation in topographic load at the Earth's surface.…”

Section: Surface Deformationmentioning

confidence: 99%

The thermal structure of mantle plumes: axisymmetric or triple-junction?

Houseman

1990

Geophysical Journal International

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S U M M A R YA mantle plume is probably a complex 3-D thermal structure that possesses approximate axisymmetry as it approaches the base of the lithosphere from below, but followed down towards the base of the layer, probably consists of a triple-junction or quadruple-junction of connected hot sheets. A relatively weak hot sheet rising only part way through the layer probably connects two neighbouring mantle plumes. These conclusions are suggested by numerical experiments on a 3-D constant-viscosity, plane layer with stress-free boundaries, which detail the gradational change in the planform of a convecting layer from the top of the layer to its base. The planform of a convecting layer is a map in the horizontal plane of the principal thermal anomalies in the layer. These anomalies are the main sources of positive (for hot fluid) or negative (for cold fluid) buoyancy, and therefore they drive the convective flow. They may appear in cross-section as structures with either axial symmetry (columns), planar symmetry (sheets) or some complex asymmetric form. When convection is driven at least partially by basal heating, the planform near the top of the layer may be described as a network of cold sinking sheets and isolated hot columns, while near the base of the layer it appears as a network of hot rising sheets and isolated cold columns. The hot columns near the upper surface arise from the vertices or nodes of the network of hot sheets on the lower surface, and similarly the cold columns at the base of the layer form below the vertices of the network of cold sheets near the upper surface. Near the upper surface, the apparent planform of this experiment is analogous to that of mantle convection, the cold sheets compared to subduction zones and the hot columns compared to mantle plumes. The hot plumes impinging on the upper surface produce approximately axisymmetric temperature anomalies, surface uplift and extensional stress fields. However, the relatively minor deviations from axisymmetry of surface observables reflect the deep structure of the mantle plume, formed by the junction of three or four hot sheets on the base of the layer. It seems likely that the commonly occurring triple-junction form of continental rifts may reflect an underlying structure that is implicit in the convective circulation of the mantle beneath.

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Tomography, the Geoid and Plate Motions

Gable

O’Connell

1991

Reviews of Geophysics

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Surface deformation, gravity and the geoid from a three-dimensional convection model at low Rayleigh numbers

Cited by 13 publications

References 11 publications

Deformation of the NE Basin and Range Province: the response of the lithosphere to the Yellowstone plume?

Deformation of the NE Basin and Range Province: the response of the lithosphere to the Yellowstone plume?

The thermal structure of mantle plumes: axisymmetric or triple-junction?

Tomography, the Geoid and Plate Motions

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