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Joined 2026-09-21 Message
Incoming links: Lithosphere
Past exam of the mathematics course of the University of Cambridge 2015 iii Paper 59 4 g Solution Created 2026-10-03 Updated 2026-10-06
For typical well-mixed structures, the dominant processes are:
- Gas giant interiors: efficient convection through most of the deep fluid envelope; radiative transfer releases the heat near the photosphere.
- Rocky interiors: slow solid-state mantle convection over geological time, with heat conduction dominant across the rigid lithosphere. A liquid core can also convect; being solid does not prevent creep-driven heat transport in the mantle.
- Weakly irradiated giant atmospheres at –: usually convection in the planetary troposphere, becoming radiative near and above the tropopause. The transition pressure and cloud or compositional effects vary between planets.
- Strongly irradiated hot Jupiter atmospheres at –: usually a stable radiative region; the deep radiative-convective boundary can lie at substantially larger pressure. Atmospheric winds also redistribute energy horizontally.
Representative temperatures must specify the level: Earth has about at the surface (about effective emission temperature); Jupiter has about near one bar (about effective temperature); hot Jupiters commonly have photospheric temperatures of order –; and the Sun's photosphere is about . Upper layers, nightsides, deep interiors and the solar corona have different temperatures. These are characteristic values, not constant temperatures throughout each atmosphere.
Past exam of the mathematics course of the University of Cambridge 2015 iii Paper 59 4 h Solution Created 2026-10-03 Updated 2026-10-06
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.
- 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.
- 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.
- 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.
Plate tectonics 2026-10-06
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.