The periods in the geologic time scale represent large intervals of time in Earth's history, ranging from tens to hundreds of millions of years. They are divided based on major changes in the fossil record, rock layers, and other geological events that took place during those time periods, such as the appearance and disappearance of different species, mass extinctions, and the formation of new geologic features. The periods provide a framework for understanding the complex history of the Earth and the evolution of life on our planet.
