To penetrate the barrier and reach the magma below, they intend to detonate an atomic device at the bottom of the hole.

The leader of the project, Dr. Stephen Sorenson (Dana Andrews), who is secretly dying of cancer, believes that the atomic device will burn its way through the barrier, but the project's chief geologist, Dr. Ted Rampion (Kieron Moore), is convinced that the lower layers of the crust have been weakened by decades of underground nuclear tests, and that the detonation could produce a massive crack which would threaten the very existence of Earth.

The atomic device is used and Rampion's fears prove justified, as the crust of the Earth develops an enormous crack that progresses rapidly along a fault line, causing earthquakes and tsunamis along its path.

Sorenson remains at the underground control center to record the event, despite pleas by his wife Maggie to evacuate with the rest of the project staff.

[1] Variety wrote that it was more believable than the usual science fiction premise and praised its special effects.