began about 540 million years ago as the global super-continent Pannotia was breaking up

is the scientific study of the origin, history, and structure of Earth and the processes that shape it

began about 65 million years ago with the Cretaceous mass extinction and continues to the present

began with the formation of earth about 4.6 billion years ago

began about 250 million years ago after the Permian mass extinction

A long and distinct period of history with a particular feature or characteristic

A length or portion of time

A period of time in history or a person’s life, typically one marked by notable events or particular characteristics

A very long period of time