crevice vs volcano

crevice and volcano both are nouns.

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

As nouns, volcano is a hyponym of crevice; that is, volcano is a word with a more specific, narrower meaning than crevice:

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

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