era vs geological era

era and geological era both are nouns.

Word	Noun	Adjective	Verb	Adverb
era	Yes	No	No	No
geological era	Yes	No	No	No

As nouns, era and geological era are synonyms defined as:

era and geological era: a major division of geological time; an era is usually divided into two or more periods

era (noun)	geological era (noun)
a period marked by distinctive character or reckoned from a fixed point or event	a major division of geological time; an era is usually divided into two or more periods
a major division of geological time; an era is usually divided into two or more periods