eruption vs happening

eruption and happening both are nouns.

Word	Noun	Adjective	Verb	Adverb
eruption	Yes	No	No	No
happening	Yes	No	No	No

As nouns, happening is a hypernym of eruption; that is, happening is a word with a broader meaning than eruption:

eruption: a sudden violent spontaneous occurrence (usually of some undesirable condition)
happening: an event that happens

Other hypernyms of eruption include natural event, occurrence, occurrent.

eruption (noun)	happening (noun)
the sudden occurrence of a violent discharge of steam and volcanic material	an event that happens
a sudden very loud noise
the emergence of a tooth as it breaks through the gum
a sudden violent spontaneous occurrence (usually of some undesirable condition)
(of volcanoes) pouring out fumes or lava (or a deposit so formed)
symptom consisting of a breaking out and becoming visible