effervescence vs natural action

effervescence and natural action both are nouns.

Word	Noun	Adjective	Verb	Adverb
effervescence	Yes	No	No	No
natural action	Yes	No	No	No

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

effervescence: the process of bubbling as gas escapes
natural action: a process existing in or produced by nature (rather than by the intent of human beings)

Other hypernyms of effervescence include action, activity, natural process.

effervescence (noun)	natural action (noun)
the property of giving off bubbles	a process existing in or produced by nature (rather than by the intent of human beings)
the process of bubbling as gas escapes