ice mass vs iceberg

ice mass and iceberg both are nouns.

Word	Noun	Adjective	Verb	Adverb
ice mass	Yes	No	No	No
iceberg	Yes	No	No	No

As nouns, iceberg is a hyponym of ice mass; that is, iceberg is a word with a more specific, narrower meaning than ice mass:

ice mass: a large mass of ice
iceberg: a large mass of ice floating at sea; usually broken off of a polar glacier

Other hyponyms of ice mass include glacier, berg, ice cap, icecap, ice field, floe, ice floe.

ice mass (noun)	iceberg (noun)
a large mass of ice	lettuce with crisp tightly packed light-green leaves in a firm head
	a large mass of ice floating at sea; usually broken off of a polar glacier