How long is an era in geologic time?
Accordingly, how many years are in an era?
How long an era lasts depends entirely on the timeframe. If you look at a 200 year period, each era may be 10-60 years and be marked by the high king of XYZ at the time. If you look back 3 billion years, each era is a few hundred million years long.
|Segments of rock (strata) in chronostratigraphy
|Time spans in geochronology
|Notes to geochronological units
|10 defined, several hundred million years
|22 defined, tens to ~one hundred million years
|34 defined, tens of millions of years
|99 defined, millions of years
Keeping this in consideration, what is an era in geologic time?
A geologic era is a subdivision of geologic time that divides an eon into smaller units of time. The Phanerozoic Eon is divided into three such time frames: the Paleozoic, Mesozoic, and Cenozoic (meaning "old life", "middle life" and "recent life") that represent the major stages in the macroscopic fossil record.
The Precambrian, Paleozoic, Mesozoic, and Cenozoic Eras The Geologic Time Scale is the history of the Earth broken down into four spans of time marked by various events, such as the emergence of certain species, their evolution, and their extinction, that help distinguish one era from another.