The very slow creep of Earth's solid silicate mantle as convection currents driven by internal heat, widely credited as the engine that carries the tectonic plates above it. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/
That the mantle convects is not in question, but whether it convects as one whole-mantle system or as separate layers above and below the transition zone was long debated; seismic tomography and gravity studies now favor whole-mantle convection at present, though the debate over deep, geochemically distinct reservoirs is not fully settled.
Facts
TimescaleExtremely slow, millimeters to centimeters per year 1 Driving ForceHeat escaping from the Earth's core and radioactive decay within the mantle itself, which make the solid mantle buoyant enough to creep slowly upward and downward over geologic time. 1 Resulting FeatureDrags the tectonic plates above it, widely credited as the underlying engine driving plate tectonics. 1 SignificanceMantle convection supplies the driving mechanism that Wegener's original continental drift lacked, the missing piece that stalled its acceptance for decades. 1 Timescale
Timescale (category) Connections
Associated With
The boundary's topography is thought to be supported by solid-state convection within the overlying mantle.
Source Core-Mantle Boundary (Wikipedia)
Geochemistry has contributed to the understanding of mantle convection.
Source Geochemistry (Wikipedia)
Causes
The slow creep of the solid mantle is the widely credited underlying engine that drags the plates above it, supplying the driving mechanism Wegener's original continental drift lacked.
Source Mantle Convection (Wikipedia)
In Discipline
Source Plate Tectonics (Wikipedia)
Open Questions
Source Mantle Convection (Wikipedia)
Sources
1. Mantle Convection (Wikipedia)
Wikimedia FoundationIntroduction, opening sentenceQuote, Introduction, opening sentence
Mantle convection is the very slow creep of Earth's solid silicate mantle as convection currents carry heat from the interior to the planet's surface.
Open Questions (1 open question)
Does mantle convection operate as a single whole-mantle system, or as two separate layers above and below the mantle transition zone, and do deep, geochemically distinct reservoirs survive within it?
Seismic tomography and mantle convection modeling now favor whole-mantle flow, but geochemical evidence for isotopically distinct deep reservoirs, drawn from differences between mid-ocean-ridge and ocean-island basalts, is difficult to reconcile with a fully mixed, single-layer mantle. The geophysics and geochemistry communities have not settled which picture is correct.
What would resolve this A model of mantle circulation that jointly satisfies the seismic evidence for whole-mantle flow and the geochemical evidence for long-lived, isotopically distinct deep reservoirs, or a demonstration that one line of evidence is being misread.
GeophysicsMantle Convection (Wikipedia)
Dissenting Readings (1 dissenting reading)
Description
Through the late twentieth century geophysicists debated whether mantle convection is layered or operates as a single whole-mantle system. Global seismic tomography showing subducted slabs crossing the mantle transition zone into the lower mantle, together with gravity-field studies, now favors whole-mantle convection, but elevated helium-3 to helium-4 ratios in some ocean island basalts are read by other researchers as evidence of an isolated, less-processed deep reservoir, so whether intraplate volcanism such as Hawaii is fed by shallow upper-mantle processes or by plumes rising from the lower mantle remains actively debated.
A dissenting reading, from Proponents of layered mantle convectionMantle Convection (Wikipedia), Wikimedia Foundation
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