An international group of scientists run Project Inner Space in Tanganyika, attempting to tap into Earth’s geothermal energy by drilling a hole to Earth’s Core. Unable to penetrate a dense layer of material, they want to detonate an atom bomb down there. What could go wrong? The leader of the project is Doctor Stephen Sorenson (Dana Andrews), whom no-one knows is dying of cancer. The chief geologist Doctor Ted Rampion (Kieron Moore) is afraid the lower crust has been weakened by underground tests and this one could literally crack the world.

The bomb is set off and—lo and behold—the crust of the world develops an enormous crack. Racing across a fault line, it causes earthquakes and tidal waves as it goes.

Rampion warns world leaders that it could encircle the Earth, and the oceans draining into the crack could generate enough high pressure to rip the Earth apart. Sorenson has found a huge reservoir of hydrogen, which is what had caused a small atomic device to become a huge thermonuclear explosion a million times more powerful. The solution, as usual, is to set off another bomb, lowering one into the crack’s path. It does not stop the crack, but it causes it to change direction.

Eventually, the crack reaches its starting point, and a chunk of the planet may be broken off and thrown into space. Sorenson remains behind, of course, to record the event, even though his wife Maggie (Janette Scott) urges him to evacuate. Naturally, her husband and Rampion have been rivals for her affection. She climbs out of the underground control center with Rampion, with her skirt ripped to the waist, and on the surface, they watch a second moon being born. I don’t know what happened to all the Africans.

The film was directed by Andrew Marton, written by Jon Manship White and Julian Zimet, and produced by Bernard Glasser and Lester A. Sansom of Paramount Pictures. It was released to high praise from critics, who called it awesomely credible and disturbing. The huge gantry was built twice, the second of balsa wood to be destroyed. Janette Scott later married Mel Tormé. She and Kjeron Moore appeared in Day of the Triffids. Dana Andrews appeared in eight movies in 1965. This is one of the better end-of-the-world movies, with a lot of angst, but plenty of action backed up by some exciting music, and it almost seems scientific.