Earth's mantle is not solid rock — over geological timescales it flows like an incredibly viscous fluid. Heat from the iron core warms the mantle from below while the cool crust sits on top. This temperature difference drives Rayleigh-Bénard convection: hot material becomes less dense and rises; cold material sinks. The result is a set of slowly overturning convection cells that carry heat to the surface and push tectonic plates sideways.
The model solves the 2D Boussinesq equations in vorticity-streamfunction form using finite differences on a 256 × 128 grid. The dimensionless Rayleigh number Ra sets the ratio of buoyancy forces to viscous dissipation. Below Ra ≈ 10³ the flow is purely conductive; above that convection cells appear; above 10⁵ the flow becomes time-dependent and complex.
The mantle convects on a timescale of tens of millions of years — a complete overturn takes roughly 100 million years. Yet in this simulation you can watch the same physics play out in seconds. The Hawaiian island chain was formed as the Pacific plate drifted over a mantle plume (a localised hot upwelling) at about 9 cm per year — roughly the speed your fingernails grow.
This simulation models two-dimensional Rayleigh-Bénard convection, the same buoyancy-driven flow that stirs Earth's rocky mantle. A fluid layer is heated from below and cooled from above; hot material expands, becomes less dense and rises, then cools near the surface, grows denser and sinks. This continuous overturning organises into convection cells, the rolling loops you see on screen, governed by the balance between thermal buoyancy and viscous drag captured in the Rayleigh number.
In the real Earth, this slow creep of solid rock over millions of years drives plate tectonics, continental drift, seafloor spreading and the formation of mountains and volcanic hotspots. Convection cells in the mantle move at only a few centimetres per year, but over geological time they recycle the entire planet's interior and shape the surface we live on.
What is mantle convection?
Mantle convection is the slow churning of Earth's solid but ductile mantle, driven by heat from the core and radioactive decay. Hot rock rises, cools near the surface and sinks, forming large circulating cells that move tectonic plates.
What is Rayleigh-Bénard convection?
Rayleigh-Bénard convection is the classic pattern that forms when a fluid layer is heated from below and cooled from above. Once the heating is strong enough, the fluid spontaneously organises into regular rising and sinking convection cells.
What is the Rayleigh number?
The Rayleigh number is a dimensionless ratio comparing buoyancy forces that drive flow against the viscous and thermal forces that resist it. Above a critical value, convection begins; higher values produce more vigorous, turbulent overturning.
How does mantle convection drive plate tectonics?
The horizontal flow at the top of convection cells drags the rigid plates above, pulling them apart at spreading ridges and pushing them together at subduction zones. This is the engine behind continental drift and earthquakes.
Mantle flow and the plates it carries move at only a few centimetres per year, comparable to how fast fingernails grow. The simulation compresses millions of years of motion into seconds.
The mantle is mostly solid rock, but over geological timescales it behaves like an extremely viscous fluid, slowly creeping and deforming. This solid-state flow is what makes convection possible.
A mantle plume is a narrow column of unusually hot material rising from deep in the mantle. Where it reaches the surface it creates a volcanic hotspot, such as the one that built the Hawaiian island chain.
The competition between buoyant upwelling and viscous resistance selects a preferred cell size, so the flow self-organises into a roughly regular array of rolls rather than chaotic motion, especially at moderate Rayleigh numbers.
Heat comes from the hot iron core and from radioactive decay of elements within the mantle itself. This bottom and internal heating sets up the temperature difference that powers convection.
Over hundreds of millions of years, changing convection patterns assemble and break apart supercontinents. The same flows modelled here have repeatedly gathered the continents together and torn them apart.