sinkhole vs natural depression

sinkhole and natural depression both are nouns.

Word	Noun	Adjective	Verb	Adverb
sinkhole	Yes	No	No	No
natural depression	Yes	No	No	No

As nouns, natural depression is a hypernym of sinkhole; that is, natural depression is a word with a broader meaning than sinkhole:

sinkhole: a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof
natural depression: a sunken or depressed geological formation

Other hypernyms of sinkhole include depression.

sinkhole (noun)	natural depression (noun)
a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof	a sunken or depressed geological formation