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Viscoelasticity, centrifugal forces and long-term stability of boundary layer anomalies in mantle convection models

Technical Report:

Abstract

Geophysical studies have revealed the existence of regions with major shear wave velocity anomalies both within the top and bottom boundary layers of the mantle. Characteristic of both anomalous regions are their steep lateral gradients, i.e. relatively sharp 'edges', and their large vertical extent into the mantle. At the top of the mantle, positive shear wave velocity anomalies are found below Archean cratons and show that the cratonic lithosphere roots extend down to 300 km from the surface of our planet into the mantle. At the bottom boundary, the two anti-podal, equatorial Large Low Shear Velocity Provinces (LLSVPs) reach up to 1000 km from the core-mantle boundary (CMB) into the mantle. At a first glance, top and bottom boundary anomalies may seem to represent pronounced low and high temperature anomalies, respectively, with associated buoyancy forces directed away from the boundaries, a state which would imply convective instability. Instead, both cratonic roots and LLSVPs have remained stable features throughout long geological time. The sharp lateral gradients of cratons and LLSVPs with the surrounding mantle are supposedly associated with strong convection currents at the sides of the anomalies. (Author)
Authors:
Publication Date:
Jul 01, 2010
Product Type:
Technical Report
Report Number:
No. 925
Resource Relation:
Other Information: Series of dissertations submitted to the Faculty of Mathematics and Natural Sciences, University of Oslo; ISSN 1501-7710; Thesis or Dissertation; TH: Thesis (Ph.D); refs., figs., tabs
Subject:
58 GEOSCIENCES; GEOPHYSICS; VISCOSITY; ELASTICITY; STABILITY; SLOPE STABILITY; EARTH MANTLE; EARTH CORE; EARTH CRUST; GEOPRESSURE ANOMALIES
OSTI ID:
1010766
Research Organizations:
Oslo Univ. (Norway). Dept. of Geosciences
Country of Origin:
Norway
Language:
English
Other Identifying Numbers:
TRN: NO1105133
Availability:
Available through interlibrary loan from www.bibsys.no
Submitting Site:
NW
Size:
vp.
Announcement Date:
Apr 11, 2011

Technical Report:

Citation Formats

Beuchert, Marcus. Viscoelasticity, centrifugal forces and long-term stability of boundary layer anomalies in mantle convection models. Norway: N. p., 2010. Web.
Beuchert, Marcus. Viscoelasticity, centrifugal forces and long-term stability of boundary layer anomalies in mantle convection models. Norway.
Beuchert, Marcus. 2010. "Viscoelasticity, centrifugal forces and long-term stability of boundary layer anomalies in mantle convection models." Norway.
@misc{etde_1010766,
title = {Viscoelasticity, centrifugal forces and long-term stability of boundary layer anomalies in mantle convection models}
author = {Beuchert, Marcus}
abstractNote = {Geophysical studies have revealed the existence of regions with major shear wave velocity anomalies both within the top and bottom boundary layers of the mantle. Characteristic of both anomalous regions are their steep lateral gradients, i.e. relatively sharp 'edges', and their large vertical extent into the mantle. At the top of the mantle, positive shear wave velocity anomalies are found below Archean cratons and show that the cratonic lithosphere roots extend down to 300 km from the surface of our planet into the mantle. At the bottom boundary, the two anti-podal, equatorial Large Low Shear Velocity Provinces (LLSVPs) reach up to 1000 km from the core-mantle boundary (CMB) into the mantle. At a first glance, top and bottom boundary anomalies may seem to represent pronounced low and high temperature anomalies, respectively, with associated buoyancy forces directed away from the boundaries, a state which would imply convective instability. Instead, both cratonic roots and LLSVPs have remained stable features throughout long geological time. The sharp lateral gradients of cratons and LLSVPs with the surrounding mantle are supposedly associated with strong convection currents at the sides of the anomalies. (Author)}
place = {Norway}
year = {2010}
month = {Jul}
}