geological time vs era

geological time and era both are nouns.

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

As nouns, era is a hyponym of geological time; that is, era is a word with a more specific, narrower meaning than geological time:

geological time: the time of the physical formation and development of the earth (especially prior to human history)
era: a major division of geological time; an era is usually divided into two or more periods

Other hyponyms of geological time include aeon, eon, geological period, period, geological era, epoch.

geological time (noun)	era (noun)
the time of the physical formation and development of the earth (especially prior to human history)	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