"Volcano" had originally aired on Comedy Central in the United States on August 20th, 1997. Similar, to the early South Park episodes before it, was slightly watched by more than one million viewers, according to Nielsen ratings. This was considered high for a cable program in the United States at the time. The Environmental Media Association nominated for the episode for an Environmental Media Award in the "TV episodic Comedy category. However, the eventual recipient of the award was The Simpsons for the episode named "The Old Man and the Lisa.
"Volcano" generally received positive reviews. USA Today critic Matt Roush praised this episode, including the "Duck and Cover" films. The Advertiser called this episode "outrageously lewd" and "hysterically funny". The Washington Post critic Tom Shales consider episode funnier than its precedent. Peter Hawes of The Sunday Star-Times in Auckland, New Zealand stated that the episode was funny and intelligent. He stated, "Once again, the US national psyche is imperishable captured by a crude cartoon". He liked the way adults were portrayed as less sensible than children, and he particularly enjoyed the "Duck and Cover" videos: "Itisterrifyinglyfunny, for it is a word-for-word recreation of the insane Atom-bomb Safety film, created and distributed in 1952 by the US government, who never for a second thought it would work". The Daily Record of |Glasgow, Scotland praised the episode and described it as "hardcore humor". "Love it or loathe it, you can't ignore the adult animation series whose bite is worse than its bark".