What geological process acts as a planetary thermostat via carbon cycling in a truly habitable world?

The carbonate-silicate cycle

For surface liquid water to persist over astronomical timescales, a planet requires an internal geological engine to regulate its climate, preventing a descent into a deep freeze even if stellar output fluctuates slightly. This regulation is achieved through the carbonate-silicate cycle. This cycle involves the geological recycling of carbon between the atmosphere and the planet’s interior. Carbon dioxide is drawn from the atmosphere through weathering processes that lock it into surface rocks. This sequestered carbon is later returned to the atmosphere via volcanism driven by plate tectonics. This mechanism acts as a thermostat, buffering the climate against slow, long-term changes in the energy received from the star, ensuring atmospheric composition—and thus temperature—remains within habitable bounds.