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Titolo:
DYNAMIC PHASE-BOUNDARY TOPOGRAPHY BY LATENT-HEAT EFFECTS
Autore:
CHRISTENSEN UR;
Indirizzi:
UNIV GOTTINGEN,INST GEOPHYS,HERZBERGER LANDSTR 180 D-37075 GOTTINGEN GERMANY
Titolo Testata:
Earth and planetary science letters
fascicolo: 1-4, volume: 154, anno: 1998,
pagine: 295 - 306
SICI:
0012-821X(1998)154:1-4<295:DPTBLE>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
SYSTEM MG2SIO4-FE2SIO4; POSTSPINEL TRANSFORMATIONS; GEOPHYSICAL IMPLICATIONS; SEISMIC DISCONTINUITIES; EARTHS MANTLE; CONVECTION; OLIVINE; MODELS; TRANSITIONS; ANOMALIES;
Keywords:
MANTLE; HEATFLOW; TOPOGRAPHY; ADVECTION; PHASE TRANSITION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
37
Recensione:
Indirizzi per estratti:
Citazione:
U.R. Christensen, "DYNAMIC PHASE-BOUNDARY TOPOGRAPHY BY LATENT-HEAT EFFECTS", Earth and planetary science letters, 154(1-4), 1998, pp. 295-306

Abstract

When radial flow passes through a mantle phase boundary, the interplay of advection and diffusion of latent heat creates ''dynamic'' topography of this boundary, which means a deflection that is related to thesense and magnitude of radial velocity even though the flow does not advect temperature differences towards the phase boundary. A one-dimensional stationary model is used to quantify the effect, which does notdependent on the sign of the Clapeyron slope. Significant deflection requires slow radial flow and a narrow phase loop. These conditions are most probably met for the phase transition from spinel to perovskiteand magnesiowustite at 660-km depth. Up to 4 km of topography (peak-to-peak) are created, with a mass anomaly that is equivalent to 440 m of dynamic topography at the Earth's surface. Other phase transitions of the olivine component also contribute to a degree that is less certain. The time scale of adjustment of phase boundary topography is studied in a two-dimensional model, where a deep mass anomaly in an isentropic mantle drives flow through the 660-km phase boundary. The adjustment time depends on the inverse square of the vertical velocity and is on the order of IO Ma in the Earth, which is shorter than the convective time scare for a high-viscosity lower mantle. Dynamic phase boundary topography created by this mechanism can replace a significant part of the surface topography required in dynamic geoid models and can help to reduce the misfit between predicted dynamic surface topography and the upper limit that observations pose on its amplitude. (C) 1998 Elsevier Science B.V.

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Documento generato il 26/09/20 alle ore 17:47:09