geologic time vs era

geologic time and era both are nouns.

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

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

geologic 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 geologic time include aeon, eon, geological period, period, geological era, epoch.

geologic 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