Mantle Convection
Mantle convection is the slow, thick circulation of rock in Earth’s mantle: hot rock rises, cool rock sinks, and material cycles over millions of years. Tectonic plates are the surface expression of this process, forming where the mantle upwells.
Mantle convection is the slow, creeping circulation of solid rock within Earth’s mantle, driven by heat from the core and radioactive decay. Hot material rises while cooler material sinks, creating a vast, fluid-like flow over tens to hundreds of millions of years. This process drives plate tectonics, with tectonic plates forming at upwelling zones and subducting at sinking zones, and is essential for Earth’s long-term thermal evolution.
What this means in real life
When you heat water in a pot, it rises from the bottom and sinks when cooled—Earth's mantle works similarly, except the 'water' is rock moving so slowly it takes millions of years to complete one cycle.
What it isn’t
It is not the same as the movement of tectonic plates themselves; rather, it is the underlying engine that pushes those plates around. The plates are passengers on the convecting mantle, not the source of the motion.
Commonly misused online
Often described as 'molten lava churning beneath us,' when in fact the mantle is mostly solid rock that flows plastically over geological timescales—not a liquid soup.