The Precambrian.
The largest divisions of time on the geological time scale are eons, which are the longest units of time and are further divided into eras. The current eon, the Phanerozoic Eon, is divided into three eras: Paleozoic, Mesozoic, and Cenozoic. Each era is further subdivided into periods, epochs, and ages.
Periods
eras
The four major divisions of time, from longest to shortest, are eons, eras, periods, and epochs. Eons are the largest intervals, encompassing significant geological and biological changes. Eras are subdivisions of eons, followed by periods, which further break down eras, and epochs, the smallest divisions, provide even finer detail within periods. These divisions help scientists organize Earth's history and understand the evolution of life and geological events.
The term "era" is not an eon in the geological time scale. In fact, the geological time scale is divided into several hierarchical levels, with eons being the largest divisions, followed by eras, periods, epochs, and ages. While eons represent vast spans of geological time, eras are more specific and represent significant developmental stages in Earth's history.
The geological division of time is as follows (from largest to smallest): Eon, Era, Period, Epoch, Age. The "normal" divisions of time in use take the form: Year, Month, Week, Day, Hour, Minute, Second.
These are put in order of older to newer. Precambrian, Paleozoic, Mesozoic, Cenozoic.
The largest divisions of the geologic time scale are: Hadean Eon (4.6 to 3.8 billion years ago) Archaen Eon (3.8 to 2.5 billion years ago; this is when the first bacteria existed) Proterozoic Eon (3.8 billion to 542 million years ago) Phanerozoic Eon (542 million years ago through today; this is when the first complex multicellular life forms evolved.)
The geologic time scale provides a timeline of Earth's history, dividing it into periods based on significant events and changes in the planet's environment. The major divisions of geological time are eons, eras, periods, epochs, and ages, each reflecting different intervals of time with distinct characteristics and geological events.
Precambrian Era, Paleozoic Era, Mesozoic Era, Cenozoic Era
Geological time eras are divided into periods, which are further divided into epochs. Each era represents a significant span of time in Earth's history, characterized by distinctive geological and biological events. These divisions help scientists organize and study the vast expanse of Earth's history.
Precambrian Cambrian