A scientist trying to better mankind nearly destroys the world as we know it in this sci-fi thriller. Dr. Stephen Sorensen (Dana Andrews) is doing research in geo-thermal energy; he's convinced that if men can find a way to drill through the earth's outer crust into the molten magma near the center, the heat can be harnessed and used to warm dwellings around the world. His assistant, Ted Rampion (Kieron Moore), is skeptical about this idea and believes that there could be dire consequences, but Sorensen boldly moves ahead with his plan, prodded by his secret knowledge that he suffers from a terminal illness and might not live long enough to undergo a longer testing period. However, Rampion's fears soon prove well founded when Sorensen's drilling causes a large crack in the earth which begins to rapidly expand, threatening to split the world in two with disastrous consequences. Crack in the World was praised on initial release for its intelligent approach and solid special effects work.
~ Mark Deming, All Movie Guide