volcano vs crevice

volcano and crevice both are nouns.

Word	Noun	Adjective	Verb	Adverb
volcano	Yes	No	No	No
crevice	Yes	No	No	No

As nouns, crevice is a hypernym of volcano; that is, crevice is a word with a broader meaning than volcano:

volcano: a fissure in the earth's crust (or in the surface of some other planet) through which molten lava and gases erupt
crevice: a long narrow cleft

Other hypernyms of volcano include cleft, crack, fissure, scissure.

volcano (noun)	crevice (noun)
a mountain formed by volcanic material	a long narrow cleft
a fissure in the earth's crust (or in the surface of some other planet) through which molten lava and gases erupt	a long narrow depression in a surface