crevasse vs fissure

crevasse and fissure both are nouns.

Word	Noun	Adjective	Verb	Adverb
crevasse	Yes	No	No	No
fissure	Yes	No	Yes	No

As nouns, fissure is a hypernym of crevasse; that is, fissure is a word with a broader meaning than crevasse:

Other hypernyms of crevasse include cleft, crack, crevice, scissure.

crevasse (noun)	fissure (noun)
a deep fissure	(anatomy) a long narrow slit or groove that divides an organ into lobes
	a long narrow cleft
	a long narrow depression in a surface

crevasse (verb)	fissure (verb)
	break into fissures or fine cracks