ice age vs glacial period

ice age and glacial period both are nouns.

Word	Noun	Adjective	Verb	Adverb
ice age	Yes	No	No	No
glacial period	Yes	No	No	No

As nouns, ice age and glacial period are synonyms defined as:

ice age and glacial period: any period of time during which glaciers covered a large part of the earth's surface

Other synonyms of ice age include glacial epoch.

ice age (noun)	glacial period (noun)
any period of time during which glaciers covered a large part of the earth's surface	any period of time during which glaciers covered a large part of the earth's surface