expanding upon vs expansion

expanding upon and expansion both are nouns.

Word	Noun	Adjective	Verb	Adverb
expanding upon	Yes	No	No	No
expansion	Yes	No	No	No

As nouns, expanding upon and expansion are synonyms defined as:

expanding upon (noun)	expansion (noun)
adding information or detail	the act of increasing (something) in size or volume or quantity or scope
	adding information or detail
	a discussion that provides additional information
	a function expressed as a sum or product of terms