An almost acceptable movie, though it didn't do the disaster justice. And the title always bugged me. Krakatoa is west of Java.
I saw it as a typical bubblegum, Saturday matinee movie, but with a better than typical cast, including the recently late Maximilian Schell (d. 1 Feb, 2014).
I think its biggest problem was the underlying mood of the situation, which they approached as a typical 1960s Hammer studio science fiction, instead of the much broader look, like in Crack in the World (1965). Because Krakatoa was a planetary event, it didn’t really lend itself to small studio work.