Interactions of scales of convection in the Earth's mantle

Nicolas Coltice, Gaspard Larrouturou, Eric Debayle, Edward Garnero

Research output: Contribution to journalArticle

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Abstract

The existence of undulations of the geoid, gravity and bathymetry in ocean basins, as well as anomalies in heat flow, point to the existence of small scale convection beneath tectonic plates. The instabilities that could develop at the base of the lithosphere are sufficiently small scale (<. 500. km) that they remain mostly elusive from seismic detection. We take advantage of 3D spherical numerical geodynamic models displaying plate-like behavior to study the interaction between large-scale flow and small-scale convection. We find that finger-shaped instabilities develop at seafloor ages >. 60. Ma. They form networks that are shaped by the plate evolution, slabs, plumes and the geometry of continental boundaries. Plumes impacting the boundary layer from below have a particular influence through rejuvenating the thermal lithosphere. They create a wake in which new instabilities form downstream. These wakes form channels that are about 1000. km wide, and thus are possibly detectable by seismic tomography. Beneath fast plates, cold sinking instabilities are tilted in the direction opposite to plate motion, while they sink vertically for slow plates. These instabilities are too small to be detected by usual seismic methods, since they are about 200. km in lateral scale. However, this preferred orientation of instabilities below fast plates could produce a pattern of large-scale azimuthal anisotropy consistent with both plate motions and the large scale organisation of azimuthal anisotropy obtained from recent surface wave models.

LanguageEnglish (US)
JournalTectonophysics
DOIs
StateAccepted/In press - 2017

Fingerprint

Earth mantle
convection
mantle
plate motion
interactions
lithosphere
anisotropy
wakes
plume
plumes
tectonic plate
seismic method
seismic tomography
preferred orientation
geoid
ocean basin
sinking
plates (tectonics)
bathymeters
bathymetry

Keywords

  • Lithosphere
  • Mantle convection
  • Plate tectonics
  • Seismology
  • Small scale convection

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

Cite this

Interactions of scales of convection in the Earth's mantle. / Coltice, Nicolas; Larrouturou, Gaspard; Debayle, Eric; Garnero, Edward.

In: Tectonophysics, 2017.

Research output: Contribution to journalArticle

Coltice, Nicolas ; Larrouturou, Gaspard ; Debayle, Eric ; Garnero, Edward. / Interactions of scales of convection in the Earth's mantle. In: Tectonophysics. 2017.
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AB - The existence of undulations of the geoid, gravity and bathymetry in ocean basins, as well as anomalies in heat flow, point to the existence of small scale convection beneath tectonic plates. The instabilities that could develop at the base of the lithosphere are sufficiently small scale (<. 500. km) that they remain mostly elusive from seismic detection. We take advantage of 3D spherical numerical geodynamic models displaying plate-like behavior to study the interaction between large-scale flow and small-scale convection. We find that finger-shaped instabilities develop at seafloor ages >. 60. Ma. They form networks that are shaped by the plate evolution, slabs, plumes and the geometry of continental boundaries. Plumes impacting the boundary layer from below have a particular influence through rejuvenating the thermal lithosphere. They create a wake in which new instabilities form downstream. These wakes form channels that are about 1000. km wide, and thus are possibly detectable by seismic tomography. Beneath fast plates, cold sinking instabilities are tilted in the direction opposite to plate motion, while they sink vertically for slow plates. These instabilities are too small to be detected by usual seismic methods, since they are about 200. km in lateral scale. However, this preferred orientation of instabilities below fast plates could produce a pattern of large-scale azimuthal anisotropy consistent with both plate motions and the large scale organisation of azimuthal anisotropy obtained from recent surface wave models.

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