= Solution
<Plate tectonics> is the movement and recycling of a planet's <lithosphere> as discrete plates over a deformable mantle. <Mantle convection>, the negative buoyancy of cool subducting slabs (<slab pull>), and gravitational sliding from elevated spreading ridges (<ridge push>) supply driving stresses; deformation and friction resist motion. The mantle mostly deforms by slow solid-state creep, rather than being a global liquid layer.
Its effects include <subduction> and recycling of crust, creation of new crust, mountain building, <earthquakes> and <volcanism>, transport of internal heat, and recycling of <water> and carbon. The <carbonate-silicate cycle> can couple volcanic CO2 supply to weathering and long-term climate.
Three major controls on a <super-Earth>'s tectonic mode are:
* \b[Mass and pressure-dependent material behavior:] gravity and mantle depth affect buoyancy and convective stresses, but high-pressure changes in viscosity and density also affect whether slabs sink.
* \b[Thermal state and heat budget:] age, <radiogenic heating>, residual formation heat and surface temperature set convective vigor, plate thickness and the strength of the lid.
* \b[<Water> and lithospheric weakening:] hydration, rock rheology, fault damage and yield strength determine whether driving stresses can break and recycle the <lithosphere> rather than leave a stagnant lid.
A larger mass alone does not establish active <plate tectonics>. The competition between driving stress, yielding and sustained slab buoyancy must be evaluated for the planet's composition and thermal history.
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