Mantle convection is the slow buoyancy-driven motion of a rocky planetary mantle. On geological timescales the solid mantle behaves as a highly viscous Newtonian fluid to first approximation.
A mobile-lid mode of planetary evolution in which coherent pieces of the lithosphere move, form at spreading regions and can recycle through subduction. Slab pull, ridge push and mantle flow compete with deformation resistance. It affects heat transport, volcanism, earthquakes and the carbonate-silicate cycle. It is not guaranteed solely by an exoplanet's mass.
Gravitational sliding of lithospheric material away from elevated spreading regions. It supplies a driving contribution to plate tectonics together with slab pull and mantle stresses.
Downward recycling of a lithospheric plate into the mantle. A sufficiently cold, dense slab can provide slab pull, while bending and friction resist motion. The resulting material and volatile recycling connects plate tectonics with volcanism and long-term climate.
A gravitational driving force associated with a dense descending slab. The slab's buoyancy and ability to remain coherent matter, so increased planetary gravity alone does not determine whether subduction occurs.
The Rayleigh number compares buoyancy driving with viscous and thermal diffusion. For a layer of thickness , temperature drop , density , thermal expansion coefficient , gravitational acceleration , thermal diffusivity , and dynamic viscosity ,Thermal convection begins when this exceeds a geometry-dependent critical value.
A local Rayleigh-number closure estimates the thickness of a turbulent thermal boundary layer by settingwhere is an order-one or geometry-dependent critical value. Combining this with Fourier's law converts the boundary-layer temperature and density differences into a heat flux law.
Penetrative convection occurs when an unstable convecting region extends into, or is capped by, a stably stratified region. Water near its temperature of maximum density provides a common example: a cold stable layer can lie above a warmer turbulent convecting layer.
Fresh water reaches maximum mass density near at atmospheric pressure. A useful local equation of state isso water becomes less dense when its temperature moves either above or below .
In an ice-covered freshwater lake, a stagnant layer colder than the density-maximum temperature can cap a warmer turbulent region. Maximizing the boundary-layer heat flux obtained from a Local Rayleigh-number closure gives an interface temperature satisfyingand a maximum upward heat flux proportional to .
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Mantle convection is the process by which heat from the Earth's interior causes the movement of the semi-fluid mantle layer, which lies between the Earth's crust and the outer core. This process is a key mechanism in plate tectonics, influencing the movement of tectonic plates on the Earth's surface. Here’s how mantle convection works: 1. **Heat Production**: The Earth's interior generates heat through radioactive decay and residual heat from the planet’s formation.