Results 201 to 210 of about 8,743 (239)

Experimental Definition of Mantle Melting and Implications for Mantle Dynamics

Mineralogical Magazine, 1994
The natural sampling of the Earth's Mantle by xenoliths or by magmas gives evidence for the presence of carbon and hydrogen within the upper mantle and extending into the Transition Zone. Models of accretion and studies of subduetion respectively provide arguments for degassing of primitive C-H species from the upper mantle and for re-cycling of ...
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Dynamics of cratons in an evolving mantle

Lithos, 2008
Abstract The tectonic quiescence of cratons on a tectonically active planet has been attributed to their physical properties such as buoyancy, viscosity, and yield strength. Previous modelling has shown the conditions under which cratons may be stable for the present, but cast doubt on how they survived in a more energetic mantle of the past. Here we
O'Neill, C. J., Lenardic, A., Griffin, W. L., O'Reilly, Suzanne Y.   +3 more
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Mantle dynamics and basalt petrogenesis

Tectonophysics, 1985
Abstract Differentiation at mid-ocean ridges generates a layered lithosphere consisting of a basaltic crust, immediately underlain by harzburgite and further underlain by pyrolite which has experienced depletion only of highly incompatible elements. The body forces driving subduction are concentrated mainly in the upper half of the lithosphere which ...
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Mantle dynamics and seismic anisotropy

Earth and Planetary Science Letters, 2010
Abstract Observations of seismic anisotropy yield some of the most direct constraints available on both past and present-day deformation in the Earth's mantle. Insight into the character of mantle flow can also be gained from the geodynamical modeling of mantle processes on both global and regional scales.
Maureen D. Long, Thorsten W. Becker
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Dynamic implications of mantle hotspots

Nature, 1974
MOVEMENT of lithosphere plates over hotspots which are fixed relative to the mantle could explain the origin of island chains and aseismic ridges1–4. Observations of phase velocities against epicentral distances for Tonga–Samoa earthquakes5 show anomalies which can be interpreted as a radial and lateral inhomogeneity in the lower mantle beneath Hawaii.
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Lateral heterogeneity and mantle dynamics

Nature, 1975
Recent work on the nature of the Earth's lateral heterogeneities yields two conclusions with implications for mantle dynamics: seismic velocity differences between continents and oceans extend to depths exceeding 400 km, and strong lateral velocity gradients at depths greater than 800 km characterise the mantle beneath many subduction zones.
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Dynamics of Superplumes in the Lower Mantle

2007
Superplumes in the lower mantle have been inferred for a long time by the presence of two very large provinces with slow seismic wave velocities. These extensive structures are not expected from numerical and laboratory experiments nor are they found in thermal convection with constant physical properties under high Rayleigh number conditions.
David A. Yuen, Marc Monnereau, Ulrich Hansen, Masanori Kameyama, Ctirad Matyska   +4 more
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Archean cratons and mantle dynamics

Earth and Planetary Science Letters, 2005
Abstract The apparent stability of Archean cratons and cratonic keels for billions of years is a difficult observation for geodynamic modeling to explain. While it may be straight-forward to assert that chemical buoyancy and high viscosity are needed to stabilize cratons, there are many questions regarding craton formation, variability (both in space
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Upper mantle heterogeneities and dynamics

Nature, 1985
The width of geochemical and residual elevation anomalies along the Mid-Ocean Ridge System decrease as both the distance between migrating ridge segments and related hotspots and the local geochemical dispersion in the anomalies increase. These observations provide further evidence that flows of mantle plumes in the upper mantle are deflected by ...
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Dynamical layering in planetary mantles

The thermal history of the Earth, it’s chemical differentiation and also the reaction of the interior with theatmosphere is largely determined by convective processes within the Earth’s mantle. A simple physical model,resembling the situation,shortly after core formation, consists of a compositionally stable stratified mantle, asresulting from ...
Ulrich Hansen, Sabine Dude
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