Potassium-40 is a naturally occurring isotope of the element potassium, which is essential for various biological functions. It makes up about 0.01% of all potassium found in nature. Potassium-40 is radioactive, meaning it can decay over time, releasing energy in the form of radiation. This process occurs at a slow rate, with a half-life of approximately 1.25 billion years. Due to its long half-life, potassium-40 is used in geological dating, helping scientists determine the age of rocks and minerals. It also plays a role in understanding the Earth's formation and the processes that shape our planet over geological time.