Toward the end of his life, Paul Newman confessed in interviews that this was the only film that he ever made entirely for the money. He called it "that volcano movie" and said that he and most of the cast knew right away it would be a flop from day one. Many people believe that part of his salary from this film was used as seed money for a salad dressing business he was setting up with A.E. Hotchner, with 100% of the profits, after taxes, going to educational and charitable organizations. As of 2022 Newman's Own, the company that Newman established in 1982, has raised over $550 million for charities all over the world, and continues to grow and prosper.
William Holden was hospitalized for six days during production to treat his alcoholism, after director James Goldstone convinced producer Irwin Allen that Holden was a danger to himself and others in the cast.
In his autobiography, Ernest Borgnine claimed that the film's special effects looked so cheap because so much of the budget went to location shooting.
Paul Newman, William Holden, Veronica Hamel, Ernest Borgnine, and Red Buttons were all under contract with Irwin Allen, and appeared in this film only to fulfill those contracts.
The bridge sequence was shot at MGM's Stage 30, also known as the Esther Williams Stage because it had a sub-floor tank that was used in her films. The bridge was 30 feet above the stage, with smoke bombs and light flashes used to simulate the lava. Doubles could not be used during filming.