soil erosion vs erosion

soil erosion and erosion both are nouns.

Word	Noun	Adjective	Verb	Adverb
soil erosion	Yes	No	No	No
erosion	Yes	No	No	No

As nouns, erosion is a hypernym of soil erosion; that is, erosion is a word with a broader meaning than soil erosion:

soil erosion: the washing away of soil by the flow of water
erosion: (geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively

Other hypernyms of soil erosion include eating away, eroding, wearing, wearing away.

soil erosion (noun)	erosion (noun)
the washing away of soil by the flow of water	(geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively
	erosion by chemical action
	a gradual decline of something
	condition in which the earth's surface is worn away by the action of water and wind