Why is geothermal energy considered renewable?

Geothermal energy is considered a renewable energy source because it is derived from the Earth's internal heat, which is naturally replenished on human timescales. Unlike fossil fuels, which are finite and require millions of years to form, the heat within the Earth is continuously generated by the radioactive decay of elements such as potassium, thorium, and uranium in the crust and mantle, as well as by friction along tectonic plate margins.123

While the heat source itself is vast and continuous, geothermal resources must be managed sustainably. If the rate at which heated fluids or steam are extracted exceeds the rate of natural heat recharge, the specific reservoir can be exhausted. However, with proper management—such as recharging the water supply or allowing for recovery periods—geothermal energy can be maintained as a sustainable and reliable power source for many years.13