chatter mark vs eating away

chatter mark and eating away both are nouns.

Word	Noun	Adjective	Verb	Adverb
chatter mark	Yes	No	No	No
eating away	Yes	No	No	No

As nouns, eating away is a hypernym of chatter mark; that is, eating away is a word with a broader meaning than chatter mark:

chatter mark: marks on a glaciated rock caused by the movement of a glacier
eating away: (geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively

Other hypernyms of chatter mark include eroding, erosion, wearing, wearing away.

chatter mark (noun)	eating away (noun)
a mark made by a chattering tool on the surface of a workpiece	(geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively
marks on a glaciated rock caused by the movement of a glacier